NavaTechnical
Document 1342 Revislon 2.0
(0
Fobruary 1900
Engineer's Refractive Effects Prediction System (EREPS) Revision 2.0
,
W, L, Patterson C. P. Hattan H. V. Hitney R. A. Paulus A. E. Barrios G. E, Lindem K. D. Anderson
S)TIC
"4,,~lF¢,.r, 7.I
Approved for publio release: dltributlon Is unlImited.
90 03
22
069
I
NAVAL OCEAN SYSTEMS CENTER San Diego, California 92152-5000 J. D. FONTANA, CAPT, USN Commander
R. M. HILLYER Technical Director
ADMINISTRATIVE INFORMATION
i
I I
This project was performed by the Tropospheric Branch, Code 543, of the Naval Ocean Systems Center, San Diego. CA, with funding provided by the Office of Naval Tpchnol ,, .Arlington, VA 22217, under program element 0602435N.
Released by H. V. Hitney, Head Tropospheric Branch
Under authority of J. H. Richter, Head Ocean and Atmospheric Sciences Division
F
I I I I I I I I
3 5
TABLE OF CONTENTS
1.0
Introduction...............................................1I
2.0
Background................................................. 2.1
Structure and Characteristics of the Earth's Atmosphere............................................ Refraction .... ........................... Index o f Re fraction.......................... ;e.2.2 Refractivity and Modified Refractivity ... 2.2.3 Effective Earth Radius Factor...............
I2.2.1 I2.2.4 ISignal-to-Noise............................. I2.4 2.2
4 4 5
5 5 7
Refractive Gradients......................... 8
2.3
2.2.5 Atmospheric Ducts...................12 Standard Wave Propagation Mechanisms................ 16 2.3.1 Propagation Loss, Propagation Factor, 2.3.2 2.3.3
16
Free-space Propagation...................... 17 Standard Propagation........................17
Anomalous Propagation Mechanisms.................... 21 2.4.1 2.4.2 2.4.3 2.4.4 2.4.5
33.0 I3.3.1
Subrefractive Layers........................ Superrefractive Layers...................... Surface-Based Ducts......................... Elevated Ducts............................... Evaporation Ducts............................
21 22 23 25 26
Getting Started........................................... 28 3.1 3.2 3.3
Hardware Requirements................................ 28 Software Support..................................... 29 EREPS 2.0 Disk organization......................... 30
EREPS Distribution Diskette Files............ 30
3.3.2 EREPS 2.0 Support Files..................... 31 3.3.3 EREPS Directory Structures.................. 31 3.4 -Program Execution.................................... 32
4.0
EREPS Programs and Routines............................... 34 4.1 PROPR and PROPH...................................... 34
I4.2 34.5 I5.2 I6.0
4.3 4.4
5.0
COVER................................................. 41 RAYS.................................................. 47 SDS................................................... 56
FFACTR............................................... 60
Modes, Key Actions, and Input Parameters................. 61 5.1 Mode Definitions...........................61 5.3 5.4
Special Function Key Definitions.................... 67 Edit Key Definitions................................ 7 Input Parameter Defijiitions............................. 73
EREPS Limitations......................................... 87
i
7.0
EREPS Models ....................... . .................. 7.1 Propagation Models ................................
7.1.1 7.1.2 7.1.3 7.1.4
89 89
Optical Interference Region Models ........ 92 Diffraction/Intermediate Region Models .... 103 Troposcatter Region Model ................. 116 Water Vapor Absorption Model .............. 120 Raytrace Models ......................... ... ..... 121 Sea Clutter Models ............ ................................. 125 Radar Models ...................................... 131 ESM Models .......................................... 134 Implementations of the Models ...................... 135 7.6.1 PROPR ....................................... 135
7.2 7.3
7.4 7.5 7.6
7.6.2 7.6.3
PROPH COVER
7.6.5
FFACTR
7.6.4
........................... .. . .... . 136 ..................................... 137
RAYS .............................. *........ 138 ................... o ................
139
8.0
Application Example ...................................... 141
9.0
Glossary ............................................... .......................................... ...
10.0 References
149 156
Appendix A
Sample EREPS products ............................ Al
Appendix B
FFACTR program source code listing
Acooslon For
NTTS
CrA&I
DT'IC T,' !
r~ wrri Ju:,f.
,,1
Nf:%t, in
Dil.,tr" Ivi.ton/ Avntl.1Uhlt ty Codo ) 1..
t
nk
. .
. .
ii
..............
Bl
I I 1
3 3 I
3 3 3 3 3 3 3 I
LIST OF FIGURES 1.
Refractivity N and modified refractivity M versus altitude for various refractive conditions ..............
9
2.
Wave paths for various refractive conditions.i.........
10
3.
An example of extended detection/ESM intercept for a surface-based radar with its associated radar hole and height error .........................................
13
4.
M-unit versus height profiles for ducting conditions.
15
5.
Incident ray and reflected ray illustrating equal angles of reflection .....................................
19
Surface-to-air geometry illustrating direct and sea-reflected paths ......................................
19
6.
..
7.
PROPR INIT mode page format .............................. 35
8.
PROPR EDIT mode, threshold direct specification .........
36
9.
PROPH EDIT mode, ESM threshold calculation ..............
37
10. PROPR EDIT mode, radar threshold calculation ............
38
11. PROPH EDIT mode, signal-to-noise versus range ...........
39
12. COVER INIT mode page format .............................. 42 13. COVER EDIT mode, free-space range specification.........
43
14. COVER EDIT mode, transmitter parameter specification .............................................
45
15. RAYS program simple raytrace ............................. 48 16. RAYS program altitude error raytrace ....................
49
17. RAYS INIT mode page format ............................... 51 1P. RAYS EDIT mode, numerical environmental input ...........
52
19. PAYS EDIT' mode, graphical environmental input ...........
53
20. RAYS EDIT mode, characteristics environmental input.
54
iii
I I I 21. RAYS EDIT mode, pressure, temperature and humidity environmental input ....................................
55
22. SDS MAP mode, Marsden square world map .................
58
23. SDS SUMMARY mode display ................................ 59 24. Two path optical interference region ................... 93
I
25. Example of 9.6 GHz height-gain curves .................. 112 26. Height-gain curve for surface-based duct of arbitary height ................................................... 115 27. Geometry for troposcatter loss calculations ............ 117 28. Raytrace Variables ...................................... 124 29. SDS summary for Marsden square 142 ..................... 142
I
3 1
30. PROPR display for X band frequency and geometries in the Greek Island experiment within a non-ducting environment . .......................................... 143 31. RAYS display for the frequency and geometries in the Greek Island experiment under surface-based ducting conditions ............................................... 144 32. PROPR display for the frequency and geometries of the Greek Island experiment under multiple evaporation ducting environments ....................................145
5
I
iv
i i i I
I I I LIST OF TABLES
1.
Relation of N and M gradients to refraction ............
i
2.
Propagation loss values from PROPR-versus-evaporation duct height for the Greek Islands experiment frequency bands and geometries described. A * indicates duct heights beyond those recommended for use in PROPR ........ 146
3.
Percent of time propagation loss is exceeded for the Greek Islands experiment as calculated by EREPS from annual duct height distributions and as observed for all seasons measured at each frequency band. Geometries as stated in text ............................................ 147
I i I I I I I I I
I I
12
3v
v
U
| 1.0
I 3
Introduction
The contents
purpose
and
Prediction stand-alone assist
I
an
System
warfare,
for
in
helpful
model
into
models with
have the
allows for
addition, replaced with
the by
use
of
and
available user's
I
and
manual
!I
program
old will
upgrade
1988).
There
to
the
Effects
individual designed
electromagnetic on
to
(EM)
proposed
radar,
The
models
EREPS
diffraction,
and
under
surface-based
horizontally
PROPH,
the
the
in
than
revision
that
a
ray
propagation
The
propagation 1.0
model 2.0
and
2.0,
that
also
Because
revision 2.0
and
now
allows
omni-directional,
1.0. in
new
EREPS
Revision
other
below,
subroutine
the
revisions
effects.
released
completely
sea-clutter
"pathloss"
loss"
code
program.
revision
term
two
1.0
described
integrate
patterns
PROPR
revision
are
between
of
ducting
to
source
to
little
to
of
1.0
this
has
been
avoid confusion
definitions.
development.
technology,
programs limit
revision source
been
systems.
an
continuing
computer
EREPS a
a
have
evaporation
applications
"propagation
is
that
of
interference,
COVER and
antenna
widely-accepted
models
is
exception
by
system
absorption
wants
very
assumed
EREPS
and
who
evaporation
was
2.0
own
changed
a
atmosphere
optical
you
Refractive
assessing
propagation-factor
their
introduce
conditions.
2.0,
anyone
single
for
programs
refraction,
(Hitney,
transmitter
which
I
to
to
is
communication
water-vapor
revision
user-callable be
EREPS
lower
from
revision
1988
programs
or
atmospheric
EREPS July
the
is
Engineer's
properly
scatter,
and
homogeneous
of
effects
tropospheric
3 3
in
electronic
in
the
IBM/PC-compatible
effects
3
of
manual
(EREPS) .
engineer
ducting,
this
operation
propagation
account
5
of
its
2.0
code
will
With
additional be
refined
discussion
consists listing.
of
to
These
programs or
EREPS
five are
new
propagation will
become
modified. revision
executable
This
2.0.
programs
i I I I.
PROPR
propagation-loss, ratio versus from which maximum
range under signal
2.
than
generates
a variety
levels range
PROPH
-
of
relative
can be
signal-to-noise
environmental
to
a
of
specified
COVER
conditions threshold
or
determined.
provides
graphics
plot
variable
is
similar
receiver
to
height
PROPR
-
orea
RAYS
traj ector ies
altitude error
summary
COVER provides
a height-versus-range
where
levels
signal
of
a
displays
series
profile,
relative
SDS
of
RAYS
-
to
SDS
evaporation
of
and
displays duct,
an
used
as
a
primary
PROPH, and COVER
6.
FFACTR
rather a program source system
incorporated
to
your
program
language.
returns
propagation
I
an
option
specified to
display
annual
of
10
I climatological
duct,
degree
the
I
and
other
latitude
earth's
by
surface.
environmental
data
10 SDS
for
the
executable program
but
5
programs.
code.
produce
might
many
source
is
require FFACTR factor
not
an
It may be a
as
you is
compiled external
stand-alone
into your programs
latter use
system
for
FFACTR
-
your
surface-based
(Marsden) squares of
longitude
for
includes
parameters
EREPS
exceed
a standard atmosphere.
degree
PROPR,
or
altitude-versus-range
rays
meteorological
be
meet
graphic
I
-
refractive-index
S.
3
rather
thresholds.
4.
1
i
tne
specified
EM
display
range.
showing
the
graphic
PROPH
independent
3.
may
a
propagation-factor, or radar
free-space
except the
PROPR
-
to
a
called
for
as
or
subroutine,
translate FFACTR
structured
in dB
program
a
into
to
the
may
be
I 3
though another
subroutine
specified environmental
that and
i
parameters.
25
I U 3
Refractive
3
A
data.
libraries sources
such
parameter,
parameter,
such as
ERz2S
value.
the
improved to
using
of
features
programming, appendix
I I I I U I I3
B.
PROPH,
results
this
available the
program
from
each
source
code
environmental
one
duct height changes
designed
of
a to
for
these In
displays.
graphics
EREPS
has
been
applications.
of
number
products
illustrate a variety
program. of
only
relative
low altitude
and SDS
suited to
to showing
manual presents
COVER, RAYS,
well
or
or evaporation
for
not
by
"stardardized propagation model"
give better
PROPR,
is
only
interactive
divergent
may differ
length; when
with maintaJ iing
that
specifically
been
has
Appendix A of from
system
wind speed
studies
comparative addition,
given
a
for
performance
sensors
of two
variety of
entering
and
IREPS
rhus,
radar pulse
as
concerned
parameters
data.
performance
the
is
IREPS
existing systems
of
of environmental
comparing one
of
portion
large
to
in-situ measured environmental
of
by means
existing EM equipments
developed
a wide
assessment to
performance
operational
provide
by
United States
the
IREPS was
1978.
since
and other organizations
Navy
been used by
that has
(1987)
al.
Patterson et
described
(IREPS)
System
Prediction
Effects
Integrated
the
to
similarities
many
contains
EREPS
FFACTR
As is
an
aid
in
reproduced in
I I I 2.0
Background
2.1
Structure
The tcgether
99
earth's
with
Excluding dioxide,
suspended
and dust, of
two most
altitude
the
the
by
components
the
mixing decreases accordance
with
The
to
the
homosphere,
the
heterosphere.
the
troposphere.
altitude
while The
8
to
equator.
It
height
temperature degrees
air
the
content
is
is
oceans, heating
which
known
horizontal
many
and
earth's
evenly
about
80
gases
gases
sulfui
occupy
about
being
surface mixing
the
to of
an the
distributes
the
kilometers,
the
tend
to
I
solids.
stratify in
the
atmosphere
is
called
stratified portion
is
called
is
called
as
and
the
by
the
the
at
the
homosphere
earth's
polar up
a
the
to
18
temperature
tropopause.
10
kilometers
temperature
troposphere
surface
latitudes,
varies
an
to
12
at
decrease
ceases The
to
to
average
the
except
troposphere rivers
land wind
and
of gas
and
components
for water
comes
from
circulations
surfaces which
4I
the
vapor.
The of
reservoirs. produces
distribute
3
vertical 6
and
7
3
troposphere
I
water vapor water
from
Differential vertical the
I
decrease
between
evaporation
other water
ocean
of
3
with
per kilometer.
lakes, of
from
characterized
with height, the
higher,
latitudes,
point at
Celsius
of
At
kilometers
gradient of
little
currents
extends
The concentrations vary
liquid
80 kilometers, mechanical
bottom portion of
10
at middle
with
the
well-mixed portion of
kilometers
The
From
point where the
troposphere
of
of
of
their weights.
lower,
The
a collection
argon and carbon dioxide
atmosphere. the
Earth's Atmosphere
of nitrogen and oxygen
g~ses.
heat-driven of
is
the
such as water vapor, ozone,
volt ne with
abundant
of
particles
gases
of approximately
atmosphere
height.
atmosphere
variable components
percent
next
and Characteristics
3
and
water vr.*or
I
I I I 3
throughout
the
troposphere
rapidly
kilometers,
the
surface
it
the
condition of
the
of
At an altitude
approximately half the
con
3nt
is
the
of
1.5
of
the
only a few
Commission for
standard
having
an
Aeronavigation
atmosphere."
arbitrarily
characteristics
This
i-
selected set
reflecting
an
a of
average
atmosphere.
Index of Refraction The
bend
an
term
degree
of bending
defined as
from
refraction refers to
electromagnetic
the
velocity,
the
is
v,
in
I
wave
as
the property of a medium to
it
passes
determined by
velocity, c,
influence
I
of
the
the
through
index
of propagation earth
or
in
other
cf
the medium. refrac-ion,
free space
objects)
v 2.2.2
surface
to
the
(
1)
Refractivity and Modified Refractivity normal
varies
propagation,
number,
(away
the medium.
c
The
the
value
between index
the, efore
a
of
n for
1.000250 of
the and
refraction
scaled
refractivity, has been defined.
I
content
Refraction
2.2.1
n,
is
tropopause,
atmosphere temperature
The
with height.
International
real
--.por
is at tne surface.
pressure and
2.2
3
the
"international
hypothetical
3
At
1925,
the
water
waLer vapor content
thousandths of w'.at
defined
The
decreases
content.
In
I
troposphere.
4
ndex
atmosphere near 1.000400. is
of
not
For
a very
the
studies of convenient
refraction, N,
At microwave
earth's
called
frequencies,
the
I I I relationship for
air which contains
(n N N-n-
I)
refraction n and
index of
the
between
water vapor
is
p 77.6 ___
+
106 0
given as
x 3.73 ____
_
T
where e
is
the
e
=
partial pressure
6.105
x
refractivity N
e
10
(
,
2)
2
T
I
3
in millibars or
of water vapor
3)
exp(x)
100
where
25.22 x
-
x
- atmosphere's
T
-
RH
Thus,
absolute
temperature
- atmosphere's
relative
humidity
atmospheric
normally vary
Since the
atmosphere
decreases therefore
the
and 400
barometric
decrease
slowly
near
refractivity
between 250
refractivity,
in degrees Kelvin
3
in percent
the
earth's
surface would
I
N units.
pressure and water-vapor
rapidly with height
with
I
pressure in millibars
barometric
atmosphere's
the
273. 2I
e
T
p
T
x log e
5.31
- 273.2)
(T
height, normally
the
while
index
decreases
of
the
content of temperature
refraction
with
and
increasing
altitude.
I
6
3
I I I 3
i i i
As
an
tool
gradients
is
M - N + 0.157 h
for altitude h
in meters
M - N + 0.048 h
for altitude h
in feet,
often used
2.2.3
in place
Effective
straight
free
line
of
the
wave
and
Therefore, straight compute
actual
I
index
that
lines.
of
with an
atmosphere
in
terms
earth
factor,
.
COVER
refractive
region and
k
for
is
related
-
1/(l
-
average to
from
a
however,
to
traveling
in
actual
replacing
the
in nature.
is
defined
as
the
the actual earth radius, a, to give Therefore a - ka. The effective e parameter used by PROPR, PROPH, and
the average
10- 6a
k,
and
of
altitude.
replacing the
radius
same
index
downward
waves
is homogeneous
radius
the
convenient of
factor that is multiplied by the effective earth radius a earth radius factor k is thee to account
bent
be approximated by
that
and
the
in a
the velocity
increasing
be
more
effective earth
by one
effective
will
travel
is
however,
space
with
frequently
may
refraction
free
decreases
effects
This
of
atmosphere
earth's
than
is
refractive
radius
Factor
propagating wave It
as 4)
electromagnetic wave will
the
normally the
The
an
the
less
line.
straight earth's
space,
their
the refractivity.
Radius
because
is
refraction
of
Earth
Within
everywhere.
II
refractive
effect upon propagation, a modified refractivity, defined
In
3
in examining
dN/dz)
-
effects
N or M unit
1 /
(10
in
the
optical
gradient by
a dM/dz)
C
5)
I I U where
dN/dz
and z is
in
and
the same
generally
taken
refractivity dM/dz
dM/dz
are
the
units to
be
conditions
- 0.118 M-units
as
N
and
M
The
mean
a.
6.371
where
x
gradients,
10
dN/dz -
earth
respectively, radius,
meters.
For
-0.039 N-units
per meter, k - 1.33
or four
a,
is
3
standard
per meter
or
thirds.
I 2.2.4
Refractive
2.2.4.1
Gradients
Standard and
It
has
Normal
I
been observed that
the
within
the
atmosphere
is
height,
Bean
(1966).
exponential
the
earth's
close
to
regular however,
The
surface
to
allow
function by a linear by
the
known of
39
effective as
a
conditiun are wave
path
cause and
known as normal
and
or an
increase
modified
per
to km
a or
of
is of
1.
refractive standard between
of
function
N
with
This
of
height
is
sufficiently
the
exponential
function which linear
is
118
M-units
function
profiles
Figure
2
gradient.
gradient 79 and
per
but
is
for
this the that
between per
3
The
Gradients
157 M-units
gradients.
km.
illustrates
vary
3
assumed
characterized by a decrease
refractivity
in figure
standard
similar
N-units
decrease
approximation
radius model.
illustrated a
an
distribution
exponential
(within 1 kilometer)
gradient
and
for
effects
-79
earth's
per km
refractivity
refractivity an
function, a linear
standard
N-units
nearly
0
km are
3 3
I I I I 8I
I I I I I
4K
Lo
3K~o
Superrefractioi M
E
2K
S R
Standard refrac
on
Subrefraction
I 8
Figure
I I
1:
altitude
increasing
various
value
upward
This
is
termed in
N
the
350
N
458
550
650
750
MODIFIED REFRACTIVITY M UNITS
and
modified
refractivity M
versus
conditions.
of the atmosphere produce and humidity distribution
with
height,
energy
it
still
systems'
refractivity
the
would
subrefraction.
nature,
subrefraction.
I I
of
and
electromagnetic the
420
refractive
the motions temperature
bend
occurs
320
Subrefraction
If the
where
2?-0
REFRACTIVITY N UNITS
Refractivity
for
2.2.4.2
120
travel
Although
must
be
performance.
profiles
and
wave
the
path away
this
wave
path,
I
situation creates an
would from
actually
the
earth.
situation
rarely
considered Figures
a
when and
2
assessing illustrate
respectively,
for
I I I I I SUBREFRACTION
Figure
2:
2.2.4.3
STANDARD
Wave paths for various refractive conditions.
Superrefraction
As
discussed
in
section 2.2.3,
a standard atmosphere
has
" refractivity gradient which causes waves to bend downward from If the troposphere's temperature increases with " straight line. height (temperature inversion) and/or the water vapor content gradient will decreases rapidly with height, the refractivity decrease downward refractivity
from the from
standard.
The
propagating wave will be bent
As the a straight line more than normal . gradient continues to decrease, the radius of
curvature for the wave path will approach the radius of curvature for the earth. The refractivity gradient for which the two radii of curvature are equal
is referred to as the "critical" gradient.
At the critical gradient, the wave will propagate at a fixed height above the ground and wil.1 travel parallel to the earth's
10
I I I 3
surface.
Refraction between the
known
superrefraction.
as
refractivity
profiles
*
superrefraction.
3
2.2.4.4
critical
3
I
the
the
I
wave
refractivity
and
path,
the
radius
earth
and
reenter
the
area
downward
refraction.
trapping
since
the
troposphere.
The
tropospheric
"duct"
noted
that
true
sense
prevent
of
the
gradient of
2
gradients
is
illustrate
the
respectively,
for
earth's
undergo
a
of
wave
surface
of
the
escape
illus trate
the
respectively,
for
Table
1
for
of
waveguide since
energy
ref ractivity
will or
condition a
narrow
confinement "waveguide."
is
there from
the wave
wave
will
enter
not
are
the
prof iles
causes
is
called
region
and
is
in
rigid walls
guide.
the a
should be
a waveguide
no
a
only
region of
It
the
either
gradient which
to
this
or a tropospheric
word
the
refracted back upward,
confined
common term
for
beyond
reflection,
refractive
is
tropospheric
the
and
refractivity
This
decrease
curvature
standard refraction and be
associated
I I I 3
the
gradient,
region of
3
Figures
and
smaller than that
strike
to
and critical
Trapping
Should
become
normal
Figures
1
the wave
the
which and
2
path,
trapping.
summarizes
refractive
the
conditions.
refractivity
gradients
and
their
Table
1
Relation of N and M
gradients
to refraction.
N-Gradient
Trapping
<
-157
<
Superrefractive
-157
Normal
I I I I
M-Gradient
N/km
48 N/kft
<
0 M/km
<
0 M/kft
to
-
79 N/km
0
to
79 M/km
-
48 to
-
24 N/kft
0
to
24 M/kft
-
79
to
0 N/km
79
to
157
-
24
to
0 N/kft
24 to
48
>
0 N/km
>
157
>
0 N/kft
>
48
Subrefractive
I
U
M/km M/kft
M/km M/kft
I 2.2.5
which
Atmospheric
Ducts
As
in
defined
section
electromagnetic energy can
propagate energy within system's than for
energy
makes
one degree. lower
for
a
given
in order
Thicker
within
the
not
of
duct's
only
the
the
the
must
relationship
to assess
duct,
ducts
give
duct,
detected,
For may be
example, missed
duct and
the
target
is
coverage
is
known
as
duct
angle
in general
be
the
can
if the
also
target radar the
a
radio
radar or
12
the
receiver to
the
duct
ranges
duct
normally
or just above
This area of
"hole" or
for
effect
transcend
which would
i
frequency.
a dramatic
which
duct.
trapping
as
is within
just above
less
well
have
U
refractivity
radar detection
systems
an air
as
I
To
usually
at any particular
extended
in
electromagnetic
distribution of
effect
ranges.
support
considered
may
a channel
small,
transmitter and
they
is
over great
duct must be
transmitter/receiver
boundaries.
a
propagate
The vertical
situation
Ducts systems
a
with
frequencies.
geometrical
upon
2.2.4.4,
be the
reduced
shadow zone
and
I I 3
I
I 3
is
illustrated by
although the
duct
waveguide does for
I
like
It
should
a waveguide
surface
in
the
case
be for
of
is continually "leaking"
Therefore energy the energy
acts
3.
emphasized
that
the
this
energy,
not have rigid and inpenetrable boundaries, except
earth's
the
figure
surface-based
level within a radar hole may be
detection, it may be
the
from
duct.
ducts. While
insufficent for radar
sufficient for ESM intercept of the
radar.
' ITRAPPING
.REDUCED RANGE
TAPPING
:
I
-
>-~.ERROR
/
"
3
INTERCEPTOR
I 3
Figure
3:
An example of extended detection/ESM intercept for a
surface-based radar
3
its
associated radar
hole
and height
error.
I
a number of meterological conditions which will
There are lead to such
3
with
the
is
as
to or at
located
duct.
ducts.
that the base of the duct
referred to close
creation of
at
an
elevated duct.
the eaith's the
There are
is
If these conditions occur aloft above the surface,
the
duct
is
Should these conditions occur
surface such
that the base of the duct
surface, the duct -is referred to as
a surface
three catagories of surface ducts depending upon
13
I I I the
condition which
meteorological
location of These
are
commonly a surface
trapping layer
the
IREPS and
referred to by
created from
surface duct
created by
immediately
adjacent
latter
is
a nearly
as
an
duct
referred inputs EREPS
to
the
for
models
do
to
distinction constitutes
not
ducting. between the
rapid the
decrease
allow
however,
trapping
Of the
a
trapping gradient
layer and
feature,
surface
Figure
4
of
the
the
this
for
duct
it
duct. created
elevated,
figure
4,
Tz
sperate
illustrates
surface,
for
and a
humidity
evaporation
particular note within actual
layer,
Because
provides
the
for
layer.
profiles
relative
of
EREPS and
the
surface.
trapping layer,
world-wide
duct
the
interface.
air-sea
permanent
to
and
a surface-based duct;
a surface-based
surface-based
refractivity
evaporation
a
duct
elevated trapping as
EREPS
evaporation duct.
from a surface-based modified
relationship
duct created from an
a surface
duct
in
the
creates
is
the and the
3
troposphere which
resultant
duct.
I
I I I I I I I I
I I I I I
, i
w
SURFACE-
TRAPPING LAYER AESED
SURFACE DUCT
BASED
TRAPPING LAYER
DUCT
,I
I
i/
MODIFIED REFRACTIVITY (M)
I I
(a) Surface duct created from an elevated trapping layer
MODIFIED REFRACTMTY (M) (b) Surface duct created from a surface trapping layer
I, ELEVATED DUCT
TRAPPING LAYER
EVAPORATION (
DUCT
I' MODIFIED REFRACTMTY (M) (c)
Elevated duct created from an elevated trapping layer
Figure
I
4:
M-unit versus height
EVAPORATION DUCT HEIGHT
MODIFIED REFRACTIVITY (M) (d)
Surface duct (evapontlon duct) created by a decrease of humidity Immediately adjacent to the sea-surface
profiles for
ducting conditions.
I I I 2.3
Standard Wave Propagation Mechanisms
2.3.1
Propagation Loss,
PROPR propagation ratio,
and
PROPH
loss,
EREPS,
of
the
occur
loss:
at
factor,
The
The
results
or
ratio,
radar
in
terms
of
1
signal-to-noise
of
each
same
as
I
the
I
term,
the
the
in
dB,
of
direction of maximum
power
received
at
any
dB,
of
the
I
antenna.
The
factor:
range
expressed
in
to
the
in free-space
in
expressed
ratio,
strength at a point to
the
Signal-to-Noise
definitions
transmitted
an omnidirectional
field
their
antenna pattern
Propagation actual
dB.
radiated power
radiation point by
in
Factor,
is
Propagation effective
present
propagation
all expressed
used within
Propagation
field strength that
in the
would
direction of maximum
I
radiation.
the
signal
noise
received at
generated within
EREPS, target
the of
of
the
etc.),
and
the
radar
loss
used
patterns are
are
based
on
pattern and
is
allowed.
loss the
is
antenna
related
of
the
radar
itself. upon
the
as
radiated power,
used within EREPS 1.0
to
many
generally
absolute
because
Widely-used
to
specified. definitions includes
gain of
the
163
2.0
antenna
in place
PROPR
path
effects antenna,
a
gain,
of
of path and
loss
the
antenna loss
PROPH,
when
an
loss
is
Propagation of
from
factors.
definitions In
of
engineering
directional
antennas.
equivalent is
the
the
purposes
reflection
all
of
dB,
in
receiver to
For the
cross-section,
(such
revision
loss
omnidirectional
Transmission
based
omnidirectional
propagation
closely
is
expressed
ratio,
the applicable propagation
in
now
input
receiver
radar
Propagation loss path
the
level
specified
parameters losses,
signal
The
ratio:
Signal-to-noise
transmission from both an
loss.
I 3
antenna
whereas propagation
I
I
I loss to
only
1
includes
(i.e.
Therefore, *
plus
the
0
EREPS
to
indicate
that
the
pattern.
I
2.3.2
others
as
transmission free
are
case
of
Free
the
electromagnetic
front
influences
would from
is
of
transmission.
transmission
loss
factor
is
factor,
included. it
to clearly
We
chose
is consistent
you should the
frequently
be aware
effects
of
to
with
that the
the
antenna
electromagnetic wave propagation between a transmitter is
over The to
the aid
defined
homogeneous, earth's
wave
front
transmitter.
a ray.
with
are
include
space
of the
transmitter
illustrated
2.3.3
the
followed
define the
propagation
However,
isotropic,
the
from
to
factor because
a wave
from
directions
maximum
normalized
Propagation
space.
properties
the gain
pattern-propagation
factor does
simplest the
of
equal
antenna pattern effects
Free-space
with
in dB.
term propagation
SThe
*
by
direction
definition of
propagation
*
in
the
loss would be
term propagation loss.
EREPS
I
in
antenna gain
referred
the
dB)
pattern effects,
propagation
The
retain
the
time,
as
and
a
and
region
loss-free,
atmosphere. spreads
In
whose
i.e.
free
uniformly
If a particular point on
the
of
in
all
a wave
collection of point positions
receiver. rays
away
space,
ray would coincide with a straight the
is
a receiver
Often wave
such as
in
figure
line
propagation
is
2.
Standard Propagation
Standard mechanisms
propagation
and processes
atmosphere.
These
propagation,
optical
diffraction,
and
that
mechanisms occur
propagation
in the
scatter.
17
those
(or
propagation
presence of
mechanisms
interference
tropospheric
are
are
surface
a standard
free-space reflection),
I I I 2.3.3.1
Optical
When large
surface,
reflected that
an
ray,
The
of
of
the
sh
reflection surface,
energy
is
This
strikes
a
portion
of
the
equal
energy
is
to
that
of
the
5.
reflected wave
the
smooth
propagating along a path
surface
figure
nearly
is
determined by the
dngle
of
the
frequency
incidence,
and the
reflecting surface.
incidence
is
line
in the also
with
as the
strong
process of sight,
upon
the
as
near the
For
as
(i.e.,
As
and
the
near
the
rougher
transmitter
illustra:J-' by
figure
also
energy
in
a portion of wave
toward
motion. the
received by to is
the
incidence wave).
paths
ability
backward reflected
typical
two
initial
is
a
seas,
unity
grows
results
backward
energy
radar's
are
reflection,
direction of
reflected
smooth
and
ocean surface
decreases.
reflection the
angles
coefficient
almost
backward reflected interfere
the
radiation,
stated above,
propagated
target.
the
reflection
within
a
Reflection
a value which depends upon
coefficient
the
Az
This
if
llow
wave
ocean,
illustrated by
of
wave
and continues
with
speed increases,
wind
receiver
the
the
reflected
may
as
the
surface
coefficient,
For values
as
angle
polarization
roughness
of
such
strength
reflection
is
electromagnetic
from the
makes
incident
and
an
Interference and Surface
the
to
a
6.
energy
I
A portion
transmitter. the
distinguish
radar aid a
desired
called clutter.
I I I I
I I I I I
"~~%)
) 'C'E,
I Figure *
angles
5: of
Incident
ray
and
reflected
illustrating
II ~OR RADAR
I
equal
reflection.
I
I
ray
RIVER OR TARGET
|
TRANSMITI ER
I Figure
6:
reflected
*i
Surface-to-air
geometry
paths.
19
illustrating
direct
and
sea-
I I I Not only
is
the
but the phase of the vertically polarized change two at
upon
or more
arrive at and
the
in
space,
the
same
electric
of
field
phase,
As of
the
in
the
direct
varying
taken
of figure
object.
reflected
of
phase
is
the
geometric
6 changes,
wave
also
arrive
and
the
sum
the
two
resultant
arriving
of
the
The
the
may vary up
at
results
receiver
received
signal
to
which
lengths
6 dB
signal
strengths
above and
in
of
the
20 dB
transmitter
tends
to
follow
is
radiation
radiation
and
the is
and
referred to
as
to
optical the
changed
radar
In
by
that
or the
the
of
an
direction
of
spreads
into
object
earth-atmosphere
point
distance to
the
of
(using an effective
and optical
the
it
geometrical
frequencies,
surface
refractive
tangent
this
curved
which
straight-line
is just
as
the
so
an opaque
the
nonhomogeneous atmosphere radar
process
atmosphere,
referred
along
field.
receiver
a homogeneous is
m
or
i
shadow region of the
I
together
relative
change,
difference.
vector
diffraction occurs where
at
either of the
waves
interfere
interfere
free-space value.
Diffraction
propagating
earth
than
waves
Diffraction
Energy
For
If two
constructively
two
reflected path
reflected wave,
in
intersect
interfere.
I
phase
different paths
greater
destructively
which
lies
180
the
Whenever
to
the
angles, degrees.
they
If
For horizontally or
grazing
said
in phase,
direct and
2.3.3.2
low
are
alone.
and
and
the
altered.
reduced,
weakened.
path
amounts
below
at
reflected wave
approximately
they
strength,
more,
also
the
traveling over
geometry
direct
of
field strength is
is
the
is
point
they
strength
is
waves
trains
component waves out
wave
reflection wave
a point
magnitude
this
which
system,
between
the
earth's surface.
tangency
with
horizon. earth
point
horizon,
the
of
the
For
radius) tangency
a
and is
respectively.
I 20
I I i The I
beyond the
ability of horizon by
frequency. The diffracted.
I I
diffraction
lower
the
is
radar frequencies
the
optical
horizon
propagate
dependent
the
the
more
the wavelength
wavelengths,
to
highly
frequency,
the earth's dimensions At optical frequencies
is
upon
wave
is
small when
and little energy is or very short radar
represents
the
approximate
boundary between regions of propagation and no propagation.
2.3.3.3
Tropospheric At
I
electromagnetic wave
compared to diffracted.
dominated
5
At
the
Scatter
ranges far beyond the horizon, the propagation loss is by troposcatter. Propagation in the troposcatter
region is the result of within the atmosphere's
scattering by small inhomogeneities refractive structure as discussed in
section 7.1.3.
2.4
Anomalous Propagation Mechanisms
leads
A deviation from the normal atmospheric refractivity to conditions of subrefraction, superrefraction and
trapping as explained in sections 2.2.4.2,
2.2.4.3,
and
2.2.4.4
respectively. The term anomalous propagation, or non-standard propagation, applies to any of the above listed conditions but it is most often used when describing those conditions which lead to radar ranges beyond the normal. Many anomalous propagtion effects may be seen quite well with a raytrace program such as RAYS.
I 2.4.1
I
Subrefractive Layers As stated
in
section 2.2.4.2,
the troposphere would cause
a subrefractive
layer of
the propagating energy to bend upward
21
I I I or away from the earth's
surface,
thereby leading
to decreased
detection ranges and shortened radio horizons. Altitude errors for height-finding radars will also become evident in a
I
subrefractive environment. Subrefractive
layers
may be
found both at
the
earth's
surface or aloft. In areas where the surface temperature is greater than 30 degrees Celsius and relative humidities are less than
40 percent
(i.e.
large
desert
and
steppe regions),
heating will produce a very nearly homogeneous often
several hundreds
of
meters
thick.
surface
Since
this
solar layer,
layer
is
unstable, the resultant convective processes tend to concentrate any available moisture near the top of the layer. This in turn creates a positive This
layer
may
evening hours,
N gradient or
retain
its
subrefractive
subrefractive
especially
if
a radiation
stratum aloft.
nature
into the early
inversion develops,
trapping the water vapor between two stable layers. For areas with surface temperatures between 10 and 30 degrees Celsius and relative humidities above 60 percent, i.e. the western Mediterranean, Red Sea,
Indonesian Southwest Pacific,
etc.,
layers may develop during the
surface-based subrefractivc
night and early morning hours. advection
is characteristicly caused by
(blowing horizontally) of warm,
relatively cooler and generally
It
more
drier
intense
surface.
than
While
may
over
N gradient the
also be
a is
layer is found
in
Superrefractive Layers Superrefractive
2.2.4.3,
are
variations large
the
that described above,
often not as thick. Similar conditions regions of warm frontal activity.
2.4.2
moist air
largely near
scale
the
conditions,
associated with earth's
subsidence
surface.
(slow
223
as
defined
temperature
in
section
and humidity
Inversions aloft, due to
sinking
air)
will
lead
to
U
I I I superrefractive
layers
aloft.
Superrefractive layers will lead
to increased radar detection ranges and extensions
of
the radio
horizon. I
The effects of a superrefractive based
the
position
relative to the layer. penetration angle, propagation. the
Additional
U I
in the
a
Trapping
of
horizon.
the
can
an
the
layer
extension of
conditions
the
illustrated
figure
reflected
amplitudes
of
for
will
have
superrefraction
both
are
the
same.
layers will be presented
propagation
bringing
it
closer
warm
surface.
which may
lead to
be
the
changed The
pattern
EM
the
well
as
the
the as
direct
relative
the
the
of
ray
between the
duct on
angle
normal
caused by
surface-reflected
as
wave
an effect.
effect of the
the
lowest
linelobe,
surface.
ducts
occur
and
dry
in
There
are
several
the
upon
also has
relative phase
to reduce
to the
Surface-based exceptionally
The
rays.
is
lobing
ray and
6.
may
two
of-sight
conditions
is propagation beyond
normal
direct
path the
ducting
concern
the
interference of
*
is
effect
horizon however, ducting
alter
in
of
usual
Within the
Ducting
*
of an
superrefractive
discussion
propagation,
earth's
less
The steeper
Surface-Based Ducts
In
*
the
the
following section.
2.4.3
and
transmitter and receiver
angle of layer penetration.
meteorological
features
of the
Both of these factors are related to
electromagnetic wave's
because
earth's
For airborne systems, the effects of a superrefractive
layer depend upon
upon
a surface-
system is directly related to its height above the
surface.
the
layer upon
formation
when
the
comparison with
air the
meteorological
aloft air
the
conditions
of surface-based ducts.
23
at
is
I I I Over the ocean and near land masses, warm dry continental air may be this type the
advected over
the cooler water surface.
of advection are
Examples of
the Santa Ana of southern California,
sirocco of the southern Mediterranean, and the shamal of the
Persian gulf. surface.
This will lead to a temperature
In
addition,
moisture
is
added
evaporation, producing a moisture gradient trapping
gradient.
routinely leads
to
This
type
a surface
of
inversion at to
to
the
I
air by
strengthen
meteorological
duct created by
the the
condition
a surface-based
3
trapping condition, a surface duct type not modeled within EREPS. However, as one moves ocean,
this
from the coastal environment into
trapping
thereby creating
the
Surface-based ducts
layer
may
well
surface-based duct
tend to be on the
and may occur both during the
day
rise
from
the open
the
known by IREPS
surface, and
EREPS.
leeward side of land masses or
at
night.
In
addition,
surface-based ducts may extend over the ocean for several hundred kilometers
and may be very persistent
Another conditions air
method
of
is by divergence
under
a
producing
frequent as
the
during the
surface-based
(spreading out)
thunderstorm.
propagation
(lasting for days).
While
other methods,
this
it may
thunderstorm
i ducting
of relatively
method may not
still
enhance
cool be as
surface
activity, usually
on
the
order of a few hours. With
the
exception
based ducting is occurrence in more
surface-based ducts
such
conditions,
An
zone near skip
as
latitudes. with
interesting
feature
is
easily
of
time
the
increased
troposphere
activity
or
with
high
surface-based ducts
is
in which the duct has no
and well
i
wind
the
skip
influence.
a raytrace program
account for its efferts
24
is
I
decreased.
illustrated using
and a model to
with
during the warmer months,
ducting is
the normal horizon, zone
Any
frontal
surface-based
such as RAYS,
fair weather,
associated with
equatorial
mixed,
This
of
of thunderstorm conditions, surface-
3
is
included
i
3
I I I in
all
the
EREPS
duzt created this
skip
programs.
It
should be
f;om a surface-based
zone phenomenon and
noted that
trapping layer
again, is
not
the
does
surface
not
have
modeled within EREPS.
I 2.4.4
Elevated Ducts
I
Great centered cover lay
at approximately
the
the
ocean
systems, it
air
5
or
there
the is
overlaying
a
boundary
as
tradewind
the
ducts may
at vary
eastern
meters
at
the
California of
the
the
elevated
part
of
the
the
western
coast,
for duct.
an
cool,
moist
elevated ducts
be
noted
top
a surface-based In
marine
thereby
oceans
to
example,
occur
the
as warm,
air.
turning
The
dry
the
25
Elevated surface
the of
at
thousand southern 40 percent
meters. of
as
Along
10 percent
may
conditions
those
for
an
slope upward
to
continental air
duct
to
ducting
1500 meters.
same
tradewind
an elevated
600
the
referred
several
along
heated
called
the
meteorological
duct are
is
layer.
an average of
pressure
of warm, dry
is
an average of
tropical
strong
above
a surface-based duct
fdct,
elevated duct
boundary
elevation
that
a
systems
the
(often
create
occur
latitude,
high
inversion
top elevation ducts
these
air
systems,
of these
to a layer
meters
For
duct.
l I I
may
marine
part.
an average
of
resultant
tropical
an average
should
become
intensify
of
of Japan, elevated
It necessary
top
layer
and
south
of air which
leads
from a few hundreds
time with
*
inversion
Within
This
The
and
Poleward
subsidence
moist
pressure
and equatorward,
"tradewinds." scale
high
north
world.
westerly winds
cool,
the
surface
degrees
the
layer).
time with
the coast of
of
large
marine
the
30
undergoes compression.
condition
3
areas
mid-latitude
easterlies
as
semi-permanent
glides
inversion
into
a
may
over also
surface-based
I I I 2.4.5
Evaporation Ducts
As
can be
seen
from equation 2,
distribution without an accompanying lead
to
a
with the meters there
ocean's
above
is
some
trapping
a
vapor
surface
the
well
above
height;
will
cause M
height, reaches
as
but to
the the
two
in
meters
all
the
of
northern
the
have
is
The
in
the
and,
figure
usually
thereafter, 4.
The
over the
that the
strength
strength
is
also
atmospheric stronger
or a
its
ability
nights
function
conditions,
signal
strengths
of
be
(or
less
M
some a
degree,
meter
On
a world
duct
meters.
"height" is in order
located
relates
radiation. For
generally
to
The
to
the duct
unstable result
propagation-loss)
than
in do
U
weaker winds.
Since
the
surface-based trap
energy
evaporation systems
above
i
or
to as much as 40
velocity.
stronger winds
with
which
approximately 13
trap
wind
decrease
at
days.
evaporation
to
to
from
extended propagation, but a value which
duct's
of water
increase
ocean, to
an antenna must
below which
to
duct.
summer is
surface
height
varies
height
during
few
water vapor distribution
latitudes during winter latitudes
A
saturated so
the
M,
also
in contact
rapid decrease
evaporation
exist
air
can
vapor.
from
The
evaporation duct height
a height
not
the moisture
change
water
pressure
surface.
The duct
time.
It should be emphasized not
vapor
is called the
in equatorial
average,
air
a minimum
Evaporation ducts almost
the
in
modified refractivity
illustrated
a minimum
gradient.
at greater heights
reach
temperature
saturated with
of water
initially causes
with
is
surface,
decrease
value
refractivity
a change
evaporation
duct
is
highly
duct 3
discussed
in
frequency
is only
GHz.
duct
is
much
section
2.4.3,
dependent.
strong enough
weaker its
than ability
Generally,
the to the
to affect electromagnetic
5
I
I I I
The proper assessment of the evaporation duct can only be performed by making surface meteorological measurements and
I(1965)
at
occurring
of
advent
interface,
a radiosonde or
processes Jeske
demonstrated by
as
a microwave
high resolution
newer,
meteorological
The evaporation duct height cannot be
(1985).
and Paulus
the
from
height
air/sea
the
measured using the
duct
the
inferring
With
refractometer.
lowered
sondes which may be
to the surface from a ship, the impression is given that the For practical evaporation duct may be measured directly. applications however, this impression is false and a direct
3
*
of
the
troposphere at
one
measured
at
another
*
conditions
The
I
evaporation for most
time,
of an
that
the
areas
of
measured
is
statistical readily
refractivity not two
be
the
profile
same
as
measurements
profile
would
not
evaporation ducting conditions,
available
the world.
2 I I I I
the
assessment system must
long-term ducts
average
any
a
likely
even when
Therefore,
apart.
representative
ocean-surface,
would most
time
measured
seconds
the
at
turbulent nature
to the
Due
be attempted.
should not
measurement
one are be the
consider.
frequency
distribution
through
the
SDS
of
program
I I 3.0
Getting
3.1
Hardware
Started
Requirements
You may
100%
PC/XT, or
run EREPS compatible
(monochrome or greater. free
Your
color).
density,
IBM
computer
EREPS
memory
2.0 is
5 1/4
required
on an
2.0
PC,
with
Personal
a
requires MS-DOS
for
n
capability
I
of
release
150
2.0
or
kilobytes
of
(RAM).
distributed on
inch,
Computer AT,
graphics
computer must have a minimum
random access
EREPS
2.0
360 kilobyte,
operation,
an
three
double-sided,
flexible
internal
diskettes. hard
double-
While not
disk
drive
is
recommended.
EREPS graphics
or
necessary
for
want
not
to
printer.
EREPS
a
2.0
copies
commercial
will
does
text
paper
graphics,
2.0
of
graphics
contain
EREPS
dumping
program
that
wide
variety
of
Technologies, 98116,
(206)
2.0
the
controlling automatically
the
with
printers 4740
937-1081,
EREPS In general,
works
Inc.,
If
2.0
output,
programs
for
is
CGA,
A
EGA,
a cost of
may be
movement
senses
the
of
used
SW,
very
Suite
and
are
many
For
CGA
good
graphics
adapters
203,
from
and
a
Jewel
Seattle,
I n
WA
approximately $50.
in place
a cursor
presence of
printer
and other vendors
available
programs have been designed
mouse
not
there
and VGA
GrafPlus,
44th Ave.
a
3
dump
is
available.
printers.
to
a printer
you have
command supplied by IBM
work with Epson-compatible
dump
capability
Therefore
operation. an
the GRAPHICS
any
m
or
to
support a mouse.
of the
arrow
crosshair.
a properly
keys
for
n
The program
installed mouse.
m
2 28
3
I I 3.2
Software
I
All
of
QuickBASIC the
EREPS
requests
and
from
products,
3.0
programs
and will
While any
we
assume
2.0
source
changes no
made
code
by
in
for
Discrepancies
encountered
directed
is
Microsoft Copies of
while
will
not
be
any problems in
EREPS
running the
and questions
within
available by
others
responsiblity
applications,
should be
written
be maintained by us.
such modifications.
for special
are
made and freely distributed
EREPS
code
difficulties
EREPS
2.0
programs may be
request,
resulting
EREPS
group.
supported
use of
the
version
2.0
a working special
Support
2.0
programs,
concerning
the
to
Commander Naval Code San
Ocean
Diego, CA 92152-5000
Fax:
ASCII
may
be
help
file,
future
technical one per
619-553-1428
us
[email protected]
provide
technical
REGISTER.DOC disk.
filled
Registration any
or commercial
619-553-1417
distribution
I U I I
553-1428
Electronic mail:
To
Center
543
Autovon:
I
Systems
out
of your
upgrades
This and
provided
file contains mailed
EREPS of
is
the
2.0
to
us
a
EREPS
on
the
2.0,
EREPS
an 2.0
the
above
address.
insure
your
receipt of
software, Please
location or working group.
29
for EREPS
registration form which
at
disks will
supporting documentation.
physical
support
newsletters,
limit
registration
or to
I I I 3.3
EREPS
3.3.1
2.0
EREPS
Disk Organization
Distribution Diskette Files
EREPS files,
revision
one ASCII
files,
an
ASCII
2.0
consists
of
five
program file,
three
binary
registration
file,
and
run-time module.
These
executable program and one
ASCII
propagation loss versus range program.
PROPH.EXE
-
propagation
COVER.EXE
-
height versus
loss
versus height
range
program.
coverage program.
raytrace program.
-
- surface
BRUN30.EXE containing
I
are
-
SDS.EXE
data
a Microsoft QuickBASIC
PROPR.EXE
RAYS.EXE
I
A
-
ducting climotology program.
Microsoft
the necessary
QuickBASIC
subroutines
and
run-time
functions
module
for execution
of any QuickBASIC program.I MSDIST.DAT duct
a binary data file
-
distribution
statistics
-
MSINDEX.DAT the
evaporation duct
RS.DAT duct
and
-
for
a binary
the
data
statistics with
a binary data
miscellaneous
SDS
file
containing
the
evaportion
program.
file containing
an
index
to
I
the MSDIST.DAT
file.
containing the
surface-based
meteorological
parameters
for
containing
a
I
the
SDS
world
map
program.
WLDMAP.ASC used by
the
-
a ASCII
data
file
SDS program.
30
I
I I I FFACTR.BAS be
compiled
-
An ASCII
external
to the
REGISTER.DOC
EREPS
an
-
QuickBASIC
source code
listing
containing
the
to
system.
ASCII
file
EREPS
registration form.
I 3.3.2
EREPS
I
With file
is
range
2.0
the
execution created
of
color the
graphics,
For
will the
files are
be
used
time
needed
A number of for
for directory
on
any
or
file
subsequent draw
the
is
height
With
the
CGA.MAP.
program
world map.
it will
be
and
first
files will
For
and SDSEGA2.map. SDS
a *.INI
installed within
be the EGA
The *.MAP
executions If any of
to
these
regenerated with
the
particular program.
EREPS programs
allow you to create
subsequent program execution. structures and
defined by the
for
binary map
adapter
this
deleted,
defaults
two
SDSEGAI.MAP
to
EREPS program,
and path names.
graphics
graphics,
subsequently
files
the
of
start-up
program, one
next execution of the
*
contains
definitions,
SDS
CGA
these
files are
data
execution
depending upon
computer.
reduce
first
created which
units,
file(s)
Support Files
file
version of MS-DOS
You are
naming using
the
customized responsible
conventions
being used.
U 3.3.3
EREPS
3.3.3.1
I
Floppy Diskettes
A necessary is
the
all file
it was
distribution is
file
BRUN30.EXE
limitations,
3
Directory Structures
In your
for
the
support
execution file.
not possible
diskettes.
directory path,
to
Therefore,
31
any
Because
include
you will
of
this
of
be
the
able
program
disk
support
unless
not
EREPS
space
file
on
BRUN30.EXE to
execute
I I I the
EREPS
programs
recommend you insuring
created.
the
the
addition,
use
seperate
SDS
it
and
as
a
and
COVER.EXE program,
is
always
then
store
backup
in
the
the
and
the
for
each
BRUN30.EXE
BRUN30.EXE
be
p-actice
to
something
on
the
a diskette should
binary
and
be
ASCII
the diskette.
create
original diskettes
case
are
file
inc.A'ed on
We
program,
COVER program,
supporting
also
good
the
distribution diskettes.
diskette
files
described above must
diskettes to
from the
example, to execute
only
For
data files
a
appropriate
For
containing
In
create
the
diskette.
directly
working
in a safe
happens
to
I
place
the
copy
diskettes.
33.3.2
Hard
For
ease
distribution MS-DOS
from
any
structure
PR.PR,
PROPH
and
Mingling
naming convention a
support
A to
separate
of
execute
the
has
system such to
the
files
one
any
files
EREPS
using
without
has
programs
however,
RAYS
requires
later
of
and
the
use
confusion. for
each
the
a
own
single
mingling COVER,
qDS
I
environmental
of
a strict
file
recommend
you
program and
its
We
EREPS
U
the
changing
capability of creating your
and
subdirectory
the
structure
program
disadvantage
files
from
subdirectory
directory
EREPS
the
avoid
all
into
single
Since you have
directory
create
be copied
of being able
files
files.
operation,
command.
directories. data
of
disk may
copy
advantage
Disk
files.
I
I 3.4
Program Execution
Any directory pressing page
EREPS
containing
the
showing
point of
2.0 program
the
contact,
the key.
program and
may be
program, You
will
name,
a brief
executed by changing typing the be
the
program name,
and
presented
with
a
revision number and date,
description
32
to
of
what
the
title a NOSC
program
U
I
I does. for
From
user
the
the
data.
your
*.INI
page,
pressed that
and
user
as
the
asked to enter current
entering
data
Any entry
used
be
is your
without
all
directory. file
you will
default path
is
assume
current
in the
The
key
program will
i
title
directory.
a path
files are
the path
name,
path
the
contained within
of a path name will be default
If
for
stored
subsequent
program use.
To attact the
input
process 4 MHz
does
machines)
there
is
the
The
program the
any graphic
inverse name
COVER
The
slight
video may be prior
prompt
has
you nlo
hesitation during turned off by
would
3
I U 33
input
data,
While this
on slow computers
type
effect upon
is drawn.
for
inverse video.
flow,
to pressing .
program,
-S options
product
a
any
with
the program
execute
I I I I
highlighted
impede
. *
is
to
not
movement. to
field
your attention
cursor
appending
a
-S
For example,
to
COVER the
the
(i.e.
-S
and
speed with
press which
I I 4.0
EREPS
Programs
I
and Routines
All of the EREPS 2.0 programs are organized into sections or
activities
editing,
called
storing or
output product;
modes.
These
retrieving data;
or
modes
allow
customizing
customizing the
for
entering,
or displaying an
EREPS program itself.
While
mode names are for the most part self-descriptive and would allow an the
inexperienced EREPS
range
operator
2.0 programs,
of
EREPS
2.0
are common between common
name
evident
and
screen
function.
At
immediate
as you
2.0
behavior. prompts any
will
direct
within
5.0
discussion
their
complete
discovered.
of
Many
a
the
3
modes
a
self-
I
mode's
HELP
mode
function key. the
full
retain
mode,
through
program,
special
the
such,
particular
you
any
F2:HELP
a
the capability of
and as
any
available by pressing the provides
be
programs
Within
will
point
to
gain operation expertise
flexibility
EREPS
access
is
Section
individual modes and
functioning.
U
I 4.1
PROPR
and PROPH
PROPR and propagation in
a
dB
PROPH
factor,
versus
calculate and
or
range
propagation mechanisms
radar signal-to-noise or
height
From the select
the
determining a illustrates
PROPR
a threshold.
Figure 9
calculating
the
Figure
10
to
threshold the
calculating the
as
I
(section 7.1)
programs are
The
optical
scatter, evaporation
illustrated
display of
in
electric
illustrates
field for
the
based
the second
of
threshold based upon
3434
in
figure
addition
EDIT mode page
threshold
illustrates
ratio
loss,
respectively.
the
tropospheric
propagation
ducting, and water-vapor absorption.
INIT mode,
quantity
graphic,
considered within
interference, diffraction, ducting, surface-based
display
upon two
ESM
the
strength.
direct
PROPH
to
7,
you may
method
of
Figure
8
specification of
EDIT
mode
system
page
for
parameters.
PROPR EDIT mode
radar parameters.
pages Figure
for 11
3
I I I
I I I I I
illustrates
the
signal-to-noise
first
of
two
PROPH EDIT mode
for
the
radar
display.
SIM
I
pages
PROPH
Select one of the following displays: 1 - PROPAGATION LOSS or PROPAGATION FACTOR us. RANGE with up to 4 user defined thresholds. 2 - PROPAGATION LOSS or PROPAGATION FACTOR us. RANGE with one threshold based on ESM parameters. 3 - PROPAGATION LOSS or PROPAGATION FACTOR us. RANGE with one threshold based on radar parameters.
I
I
4 - RADAR SIGNAL-TO-NOISE us. RANGE.
Display option Propagation model Vertical axis Height units Range units Maximum range Number of lobes
D INTERNAL PROPAGATION LOSS dB ft To set startup height and range units nmi to current units, press key F4. 0 2
Display option (1,4)
Figure
I
7:
PROPR INIT mode
page format.
I I I I I I I I Frequency in MHz (108,2088)
IBe -
88P R 0 P 118A G A T 140---
FREQ
I
M
]I'
POLARIZATION HOR 75 TRAN HT ft 30 REC HT ft SINX/X ANT TYPE 10 VER Bu deg 8 ELEV ANG deg 8 EUDHT m
interference lobe
L 0FREE-SPACE
0 SBD HT m x 1.333 339 NSUBS ABS HUM 9/m3 7.5 18 UIND SP kts RNGE
S 208
or dB THRESHOLDS
1 0 N
range 23 nrti 173.9 dB prop loss
178-
1ee
-- - - flfi
Ii
nmi 8 ...................... ...mi 0 8 --...
d....... B
238
i
I
30
40
I
18
8
28
RANGE nmi Figure
8:
PROPR EDIT mode,
i
58 FREE SPACE
-
threshold direct specification.
36
-
-
-
I I I
i I
011I63 588e-
Frequency in MHz (188,28888) FREQ om POLARIZATION
4888H E I 3888 G H T 2888f t 1888-
8-
,ESM
238 I A Figure
I
288
178
148
PROPAGATION LOSS dB INN MR AII 9:
PROPH
gR'"B Ig i'l g 6=11 I.':1
118
HOR
TRAMl HT RANGE ANT TYPE VER BU ELEV ANG
ft
75
nmi
58
EVDHT SBD HT ]( NSUBS ABS HUN LIND SP PX POW ANT GN SYS LOSS ESM SENS
n m
OMNI deg N/A deg N/A 8 8
1.333 339 g/m3 7.5 kts 18 kW 285 dBi 32 dB 8.4 dBm -88
FREE SPACE - INTERCEPT
- -
88 THRESHOLD -------PROPLOSS dB 188.1 Olx l
EDIT mode, ESM threshold calculation.
*Ir g
I I I I I I I I 0I 801311 Be-
Frequency in MHz (188,20888)
FREQ
I
]
POLARIZATION HOR 7S RADR HT ft 38 TRGT HT ft SINX/X ANT TYPE 1s VER BW deg 8 ELEV ANG deg 285 PX POW kd 1.3 P WIDTH us
P R 0 P 118A G A T 140-
I O N 178 L O S S 200 d B 238
0
10 aIq
Figure
10:
PROPR
48
28 RANGE nmi38 ifi , aII ri; i
s.
EDIT mode,
N
32 ANT GN dBi 8.4 SYS LOSS dB 14 REC NF dB 1.5 HOR BW deg 658 Hz PRF 1s SCAN RT rpm 1 sqm RCS 0.5 PD 1.8E- 8 PFA 1-FLCT SW CASE , FREE SPACE 8 THRESHOLD -----FS RANGE nmi 14.5
s v4r
radar
5lq
1
threshold calculation.
I
FrqecInM~ 10200 108IFE POAIATOIO t 7 RAG ni 1
IARH
HT
GRADR
ft
75 183
xm RHG ANT TYPE g
880
HER BiU I60
I
185
EVTFACTO
AS HN
488A/NIS Fiur
deg
X.
/
11:N
288CLUTER
,sga -o-os
8
g/3 74.5
dDTmd eg essrn DIRP BAED3O
U I The threshold display
electric is
system to
not
the
exceed
exceeds
line
on
the
the
threshold.
the
the
threshold.
representing a different
detectibility Drawing of the
the
may
single
free-space
be
as
(section
exceeds
indicate
the
reference mark,
Of are
approximate model
is
a
text
an
output
values
RPE data
verses
vehicle
for
either and
In
will
a
free-space
display
below
of
clutter.
bound signal
able
the
provided.
clutter value
the
be
is
and
suppressed within
clutter
where
threshold
transmitter power,
an average
should
to
a
the
use
of
graphic
"interference
interest
Radio
be
is
a
to
(a
(double
U
strength
function.
clutter
level
will
lobe",
data
40
a directing have been
In
line,
a
added.
of
equation
full wave
Equation
RPE will be
range.
purposes.
the Propagation model prompt.
Parabolic
output
display
labels
a stand-alone
and
for
LABEL and XHAIR modes
parabolic
consisting
height
the
the Helmholtz
computers,
file
these
cases
I
section, etc.
11,
lower
signal-to-
thresholds may be
respectively,
loss/range value
addition to mainframe computers.
as
the
with each
the
developing
the
to four
illustrates
system
solution to
named
or
degradation.
particular
currently
line
strengths
words and
loss
11
8 illustrates
add explanatory
possible for the
graphic
and
For the
is not
may be
).
the
performance
case,
8
PROPR
signal-to-noise
reference line
upper
7.3
signal
Figure
this
an
clutter,
Conversely,
We
Figure
displayed
line*or
lines)
figures
the
the
target radar cross
factor reference
OPTIONS mode.
Clutter
to
on
on
display.
receiver sensitivity,
probability of detection,
seen
or
It
Up
line
PROPH
propagation
displayed simultaneously upon any one
As
(system's performance)
a horizontal
propagation loss
function when
ratio
strength
by
a vertical
function,
ratio must
noise
represented
and as
system to
field
model
equation.
(RPE)
model.
a matrix
files.
Our In
hosted upon personal
program which will
EREPS
to
of propagation loss
will By
generate
be
the
responding
display to
the
I
i i 3
Propagation model prompt used to cause
produce
EREPS
display
While
in the
RPE
is
function
You
may
3 i
4.2
range
also
able
The
COVER
the
to
loss
display the
systems.
within COVER
are
for
presence of
data
file
the EREPS
be
and
Display
distribution,
an RPE output
file
available.
parameters
which determine
propagation loss it becomes
strength
The
graphic.
versus
the You
height
or
available.
optical
may
electric
select field
propagation
simultaneously
transmitter
The
target
Figure
specification
of
13
the
the
contours
vertical
plane
of for
considered
diffraction, evaporation
illustrated
of defining
first method
free-space
in units
displayed,
power,
sensitivity, etc. direct
methods
either by
loss
displays
and water vapor absorption.
of COVER, as
strength.
threshold directly, or by
two
in
interference,
INIT mode from
and
propagation mechanisms
ducting, surface-based ducting,
be
available
calculates
field
surface-based
you
generated
or signal-to-noise
RPE when
program
electric
From the
I I I I
of
the
will
COVER
constant
3
choose
calculated with
3
I
be
the
models
Responding with RPE will
indicated by
not currently sense
EREPS
properly when RPE becomes
physical appearance also
the
independently
fashion as
revision 2.0 will
and will
will
graphic.
read RPE's
the data
option. EREPS
to
INTERNAL,
desired
the
with
of dB. each
to
cross
illustrates threshold.
the
threshold
in units four
representing
radar
figure
is by specifying
range Up
the
in
of the
range
thresholds may a
different
section, EDIT
of
12,
mode
receiver page
for
I I I I I I I I' 3
0COVER i
Select one of the following displays: 1 - HEIGHT vs. RANGE coverage with up to 4 user defined thresholds 2 - HEIGHT us. RANGE coverage with one threshold based on radar parameters. Display option Propagation model Height units Range units faximum height faximum range
I INTERNAL ft nmi 50000 200
No. of lobes
6 C
Range axis
To set startup height and range units to current units, press key F4.
I
I I
Display option (1,2)
Figure 12:
COVER INIT mode page format.
I
I U U I I I I I l
Frequency in MHz (188,28888)
I
5Ik H
40k
E I
38k
H T
28k
FREQ
EUD HT SBD HT -.
f t
-.
18k 0 l
- 4
-.
,- ,
8e
'.
Figure
13:
COVER
EDIT mode,
nmi
180
nmi nmi
8
200
free-space range
I
I
0 1.333 ABS HUM g/m3 7.5
l
160
RANGE nmi
43
8
m m
FREE RANGES or dBSPACE THRESHOLDS
128
I
31T1Ml
POLARIZATION HOR TRAM HT ft 75 ANT TYPE OMNI UER BW N/A ELEV ANG N/A
specification.
8
I I I The threshold
second is by
parameters Figure
14
of
method
of
defining
specifying the
a radar and
illustrates
system's
parameters.
changed,
the
the
various
the
electric
electromagnetic system
characteristics
of the
the second of two EDIT mode pages Note
that
as
each
appropriate free-space
field
system
target. for the
parameter
is
range value is immediately
I
displayed. You may also
choose the
parameters
physical appearance of the cover graphic. axis prompt
i
allows
which determine the
For example, the Range
for a curved or flat earth presentation.
You
are cautioned about selecting the graphic height and range combinations employed with the curved earth display as improperly selected values may make
the coverage display
hard
to
interpret
3
or misleading upon casual inspection. The search
coverage diagram may be
radars,
either
2D or
3D;
used for
long-range
and for
communications.
should not be used
coverage
display
surface-to-air for
surface-search radars employed against surface targets or for any type of gun or missile fire-control radar unless you fully understand the limitations of the coverage models. For
surface-search
performance assessment
is the
I
for surface-search radars when
employed against low-flying air targets; The
air-
radars,
a major
target's
radar
consideration cross
section.
I I
in A
target's radar cross section is a function of the target's shape. Large, flat, smooth surfaces may reflect a large amount of energy,
but
the
scattering will be
Smaller, more angular surfaces may
not
but the area over which the energy is indeed. It has been shown ship target is not from
primarily in one direction. reflect as
much energy,
scattered may be very large
that the major energy return from a its smooth, large hull but from its
superstructure with its highly angled and complicated In addition, for very large targets, becomes a function of viewing angle.
44I
the
structure.
radar cross section also
The models employed in
3
I I I I I I I I *
g1
Frequency in MHz (188,28888)
111 J1w FREQ POLARIZATION HOR 75 RADR HT ft ANT TYPE SINX/X 19 VER BW deg 8 ELEV ANG deg
58k
3 3
H E I G H T
40k
t
I8
38k -
28k
"-,PRF
-.
0 -
-
80"-.
"
P" POW
k P WIDTH us ANT GN dBi SYS LOSS dB RECNF dE HON B deg Hz
200 60 21 6 S
rpm
6 0.5
SCAN RT PD A168 SWCASE
RANGE nmi
i
i45
Figure 14:
FS RANGE nmj
11
300
1-FLCT
95.8
COVER EDIT mode, transmitter parameter specification.
I I I generating a coverage display make the assumption that
the target
is a point
angle
source
target,
independent
of
viewing
and
composed of only a single reflecting surface. The
very
nature
of
fire-control
radars
dictates
an
antenna which trains both in azimuth and elevation.
The coverage
for an antenna aimed at the horizon will not be
same
coverage
for
is designed elevation
an antenna when aimed aloft. to
show coverage
angle.
If
the
the
as
i
the
The coverage display
of a radar with
a
fixed antenna
fire-control
radar is employed in ai search or track mode at a single elevation angle, such as may be the
case
of
a horizon search for
low-flying missile targets,
the
coverage display will produce an accurate representation of the actual radar coverage. It must be understood however, that once the elevation angle longer valid elevation
and
the existing coverage display
elevation angle,
In
addition
to
considering
the
antenna
3
the amount of energy directed toward the target
taken into account since fire-control
generally scan
the
rotates.
is
This
is no
coverage must be recomputed based upon the new
angle.
must also be
changes,
target with accomplished
a single pulse through
the
radars as
use
of
the
do not antenna
the
proper
free-space range. There are two limitations of the you
should
be
aware.
First,
COVER program
COVER
uses
a
of which
parallel
ray
approximation to the propagation model given in section 7.1.
The
3
approximation assumes that the direct and sea-reflected rays arrive nearly parallel at the receiver/target. This assumption
i
is
i
quite
good
at
>ung
ranges
and higher heights.
However, as
ranges and heights decrease the assumption becomes poorer and the COVER program will be
in error, with the error becoming worse as
ranges and heights decrease. make
the
parallel
program are
The PROPR and PROPH programs do not
ray assumption.
If the
suspect, they may be compared
results of the COVER
to those obtained from
I
5
PROPR or PROPH which will be correct for all geometries.
I
as
Secondly,
coverage diagram decreases
the
lobes will
corrected by
For
13).
the
altitude,
fail.
scale
the
some
on
spacing
lobe
For
combinations
a of
routine used to shade
graphic
these cases,
increasing the
The RAYS
program traces
electromagnetic
segmented is
(figure
the
shading problem may be
and replotting
the graphic.
RAYS
4.3
of
and
range,
frequency,
,
increases
frequenc,
rays,
the
paths,
in
15,
based
figure
height upon
refractivity-versus-altitude profile. using
accomplished
the
and
The
a
range,
linearly
ray
tracing
approximation to Snell's
-.,all angle
law.
3
The for CGA figure
3 3
RAYS
graphic
computers,
Height-finder standard
a
and
raytrace
to
COLORS modes
5.0
to make
and LEGEND modes
to
path.
For
calculated
computer
error
the as
only product
illustrated
is
in
This
for
a
in
the
height
of
by
47
upon
is
be
for is
in
a
EGA a
error or
VGA
raytrace
specified height illustrated
responding with a Y
INIT
altitude
RAYS
to your
product
discussion
the
will
configured
'>eight error color displa;
based
non-standard refractive
product
is obtained while
altitude
according
scheme.
This product
section
determine
graphic
height
color
the Alt Error prompt
Refer
I I I I
your
secondary
and
16.
ray
target's
If
this
displaying increment
the
3).
graphics,
to
product,
is a simple
radars
atmosphere
conditions,
figure
graphic
15.
(figure
3
primary
by
(yes)
or OPTIONS mode. on using
the
OPTIONS and
assignments and error
legend.
the LABEL
I
•
II
I I I I I I I I
ITransmitter
antenna height in ft (3,58888)
*
28880-
TRAN HT ft 1Z NO. OF RAYS .d HIH ANG mrad MAX ANG mrad 18 REFLECTED RAYS Y PROFILE HEIGHT(ft) H-UNITS 8 358 1888 385.96
16880H E I 12888-
G
N
I
H T f
tI 4888-
I 8
48
88
128
168
RANGE nmi Z:S P* 3:INTI:XHI' . g'I |, Figure
15:
RAYS program
*'NU
288
I
simple raytrace.
I
I I I I I I I Hove cursor to desired position and press F4 to relocate legend. 20000TRAM HT ft NO. OF RAYS
H
It. Error (ft) 8 2588 5ee 38 1888 3588 1588 4888
E
2888
4588
I 12888-
2588
>4588
16008
188 s8
HIN ANG mrad -18 MAX ANG urad 18 REFLECTED RAYS WA PROFILE CHARACTERI1STICS
G H
DUCT TOP ft
1888
DUCT BTM ft LYR THX ft
8 188
T 8888-
3
f t
8
Figure
i
16:
'048
RAYS
88RANGE xvi1280
program
168
altitude error
288
raytrace.
LYE LYR LYR LYR
TOP ft 1008 ETH ft 908 TYPE B GRD M/kft 68
LYR LYR LYR LYR
TOP ft 18888 BTM ft 17888 TYPE P GRD N/kft 15
I I I From the INIT mode of RAYS, as illustrated in figure 17, you may select from three methods of entering environmental data. You may also choose appearance
of
the
and range units Range
units
the parameters which determine raytrace graphic.
may be
they may
be
the Height units and
changed
individual prompts such as Kaximum height. exercise
caution with
physical
Note that while the height
set globally with
prompt,
the
independently You are
for
advised to
this freedom as mixing units may lead to
later confusion. Upon method
1
entering the
EDIT mode with environmental
(numerical/graphical
selected,
the
page
illustrated
Height and refractive keyboard.
height-refractivity in
figure
18 will be
unit values may now be
By pressing the
input
levels)
displayed.
entered from the
or key,
the graphical
edit page,
figure
may now be
entered with the use of the arrow keys or the mouse.
19, will be presented.
Upon entering the method page
2
(refractivity profile
illustrated in
refractive height,
figure
The refractive profile
EDIT mode with
environmental
characteristics)
20 will be
input
displayed.
For example,
a surface-based duct with a layer from 900
to
1,000
feet;
top
at
1,000
an elevated
Up
to
three
figure 20 illustrates feet and layer
a trapping
from
9,000
10,000 feet with a subrefractive M-unit gradient of 60 M/kft; an
elevated
layer
superrefractive and may
M-unit
third features be
ducts.
feature
bounds
being
recommended point.
are
specified Input
that
from
as
17,000
gradient
labeled as T
is
superimposed you do
of
15 M/kft.
layers
(trapping),
checking
not
18 , 000
to
thereby
fee t
their
upon
override
another.
the
bounds
It
a
I 3 I
second
gradients
creating
performed which will
to and
with
While the
(LYR),
U 3
selected, the
features may be specified by describing the features'
strength, and nature.
I
elevated
prevent is
checking
one
highly at
I
this
5
50
1
I I I I I I I I I
RAYS
SI~
Select one of the following environmental input methods:
i
1 - Numerical/Graphical height-refractivity levels 2 - Refractivity profile characteristics 3 - Pressure, temperature, and humidity
Enter method
I
Height units Range units Angle units Refractivity units Smoothness Maximum height ft range nmi Alt error
ft nmi mrad N-units 3 2eee
Iaximum
I
Figure 17:
I
RAYS
To set startup height and range units to current units, press key 4.
zae N
INIT mode page format.
I I I I I I I I 13I3I6 I Transmitter antenna height in ft (3,50008)TRAHT ft
Press PgUp/PgDn for graphical input.
Use INS or ENTER to add levels to profile. Use DEL to delete levels from profile. Use arrow keys to move cursor.
Figure
18:
NO. OF RAYS
58
MIN ANG mrad
-18
1o MAX ANG mrad Y REFLECTED RAYS PROF ILE HEIGHT(£t) H-UNITS 350 8 1888 385.%
RAYS EDIT mode, numerical environmental
52
too
I I I I input.
I I I I i I I I I
9 ).
II ,
NOt M)'
e
I
r
r I
Press PgUp/PgDn for numerical input. Dashed lines (standard gradient)
,
,
I
are shown for reference.
C
/
Use INS or ENTER to add levels to profile. Use DEL to delete levels from profile. Use arrow keys to move cursor.
/
, ,
':
".; :
A I]
/ C
I C
COASE
MINE
H: 188.8 Ml:
Figure
I
19:
RAYS EDIT mode, graphical environmental
C
/I
V
1:ES2HLOTOS5LBL7 :IE
I
f
/, I388
C
1
I
C:t € ,
3
C
€. ,'
C ,'C
, I;
.
C
it
,j
$
, ,
t
, I
,
,
-
1
/
input.
I
V
1119
10:PL
386.8
Upon
entering
the
EDIT mode with environmental
input
3
method 3 (pressure, temperature, and humidity) selected, the page illustrated in be
figure 21 will be displayed.
Pressure values must
entered in decreasing order.
19g13
I I I I
Transmitter antenna height inft (3,5888)
i
TRAN HT ft
NO. OF RAYS
i 188
58
HIH ANG mrad -18 MAX AIG mrad 18 V REFLECTED RAYS PROFILE CHARACTERISTICS DUCT TOP ft DUCT BTH ft LYR TH ft
Figure
20:
RAYS EDIT mode,
LYR LYR LYR LYR
18888 TOP ft 9880 BT ft TYPE Bi GRD t/kft 68
LYR LYR LYR LYR
TOP ft 18888 BTM ft 178008 P TYPE 15 GRD /kft
characteristics environmental
54I
1888 8 188
input.
i
i
I I I I I I I U m
Transmitter antenna height in ft (3,58888)
Ue ! "r ENT E ER to aAd lekiels to profile. Use DEL to delete levels from profile. Use arrow keys to move cursor.
I I
ia
7
Figure *
21:
l
I~l~
too
NO. OF RAYS 58 HIH ANG urad -18 MAX ANG mrad 18 REFLECTED RAYS Y SONDE HT ft 8 PROFILE P(mbs) THP(C) H.) 1813.2 15 88 258 -52 8
GI!ili']g~
RAYS EDIT mode,
environmental
I
ll
TRAMHT ft
Fl
pressure,
input.
55
temperature
and humidity
I I I From any page or
height
and
profile enter
keys
only
EREPS
will
longer
to
view
units
or
the
Returning
with
to
the
the
a
Once
reminder
text,
appear
on
the
the
numerical values
method
display.
of The
used
to originally
INIT page via the
key and
raytrace i.e.
the
pressing
graphical
input method will
defaults.
the
EDIT mode,
you
edited
different
screen, no
allow
be
data.
selecting a the
will
refractivity
may
the
within the
"Use
screen.
reset
the
graphic INS
or
The
environment exists
ENTER
to the
on
to add
editing
keys
will
I
3
remain active however.
If the
entered environmental profile
the
height of
the
of
118
(36
M/km
Additionally, height,
4.4
duct
graphic
display,
M/kft)
if
the
will
a standard
be
appended
does
will
be
The
program displays
extend
to
refractive gradient to
transmitter height exceeds
no rays
not
the the
profile.
3
graphic plot
drawn.
SDS
SDS
summary
The
for
an
consists
of
showing the percent
occurrence of
description which
includes
include
and
listing
wind velocity,
earth radius
The
assembled
statistics
by
assembled by is
evaporation
the duct;
percent
of
of
duct
3
a surface-based duct occurrence,
locations,
miscellaneous
average
number
of
information
to
and
refractivity value,
surface
histogram
and
effective
factor.
meteorological
analysis
a
an
source
radiosonde
observations;
surface
or more Marsden squares.
one
summary
thickness,
annual climatological
data the
the
displayed within SDS
bases;
GTE
Sylvania
National
based on
the
Climatic
Radiosonde
are
derived
Data
II
Corporation
and
Data Center.
The GTE Sylvania
approximately 3 million worldwide
56
from two
Analysis the
DUCT63
radiosonde
U
I I I soundings taken during a 1973
to
1974.
150 years obtained
The
5 year period,
DUCT63
analysis
of worldwide surface from ship logs,
observations,
from
1966
to
1969
and
is a 15 year subset of over
meteorological
observations
ship weather reporting forms, published
automatic buoys, etc.
While
the
world is
divided into 648 Marsden squares, the SDS climatology is provided for only 293 Marsden squares. This number
was
selected
for
two
reasons.
First,
EREPS
is
specifically designed for maritime application. The 293 Marsden squares cover the open ocean and coastal waters. Second, a minimum of 100 valid observations per month within a square was imposed to reduce the effects of any spurious meteorological I
measurements on the distributions. The map,
square(s) of
figure 22, by positioning
highlighting key.
3
interest is
it
(them) with a
As seen in figure 22,
(are)
a cursor
selected from a world over the square(s) and
special
function key or a mouse
as the cursor moves over the map,
its
latitude, longitude, and Marsden square position is displayed. For this example, Marsden squares 113 and 112 have been selected. The
world
average of
all Marsden
selecting the box labeled
I
Figure squares
112
23
and
obtained by
"World Average."
illustrates 113.
squares may be
In
the summary obtained from Marsden example, the surface-duct
this
statistics were obtained from a single radiosonde source, oceanographic observing station 480
West
longitude.
If
located at
more than
350
North
a fixed
latitude,
one radic ,onde source
is
located within the selected squares, their averaged observations would be provided. If no radiosonde source is located within the selected square, the closest great-circle For I
I
this
reason,
it
is
source to the location of
important interest.
source would be
to note
the
used.
proximity of
the
I I I I I I I 9-
30
-98
.
60
60
3
38
..---
30I
380
188 128 CROSSHAIR LOCATION -- > IaHMAI
A
Figure 22:
=I
60 8 35 N 45 U MSQ:113 4
idN
68
128
188
go
SDS MAP mode, Marsden square world map.
Through the use of special function keys, other functions such
as
screen
labeling
or
file
accomplished. 58
manipulation may
also
be
I I I I I I I I
IEVD HT I
I
810 T'0 2 TO 4TO 6TO
8108.
180TO 12 . 12 TO 14 a 14 TO 16 m 16 TO 18 . 18 TO 28 m 20 TO 22 22 TO 24 n 24 TO 26 n 26 TO 28 . 28 TO 38. 380TO 32 n 32 TO 34 n 34 TO 36 . 36 TO 38 n 38 TO 48 > 48 Figure
I
3m5
x OCCUR 8
2 2 m 4m 6m 8.
23:
5
--3.8-SURFACE 3.8 3.5 E 6.8 9.5 A
18
15
28
25
ANNUAL DUCT SUMMARY _
SURFACEOBS: AVERAGED 2 SQUARES
12.8 P
13.3 13.3 11.4 9.1 6.6 4.4 2.8 1.7 1.8 8.5 8.3 8.2 8.1 8.1 8.8 8.1
SDS
0 B A T I 0 N D U C T H T
SUMMARY mode display
AVG EVD HT: AVG WIND SP:
12.5. 13.9 XTS
UPPER AIR OBS: RS
4YE
FIXED SHIP, NORTH ATLANTIC OCEAN LATITUDE: 35.88 N LONGITUDE: 48.88 U SBD OCCURRENCE: 7.8 y AVG SBD HT: 128. AVG NSUBS: 352 AVG X: 1.52 SAMPLE SIZE: 2887
I U I 4.5
FFACTR
FFACTR routine,
is
a collection of
written
in
pattern propagation and environmental all(-. iou the be the
called
if the
factor
information.
at
only once. the
of
this
fashion,
it
Because may
not
compute
varying range
system
extracted
is
routine
to
may
structured
in
For example, is
desired,
initiali-ation subroutines need be
They would be
the
incorporating
particular task.
for
EM
routine
this be
callable
a
called
from FFACTR and placed within
calling routine.
code.
an
the
intent
directly.
a constant height
The FFACTR
and
The
manner for your
common application,
a
that will
own application programs,
in an arbitrary
loss
into
in dB when provided certain
propagation models
most efficient
formed
Microsoft QuickBASIC,
to create your
EREPS
models
the
Variables within
list.
A
is
the
input parameters
argument
section
routine
are
well documented within
routine are passed
to
discussion of
the
program
passed via a common block the
the
FFACTR routine
FFACTR models
through
appears
in
7.0.
FFACTR program which
is
shows
also the
provided possible
with uses
a demonstration for
the
FFACTR
FFACTR may
be compiled under Microsoft
QuickBASIC
executed as
a normal
the
program to observe
driver
I
routine.
3.0 or
4.5 and
demonstration.
I I I I I 60
I I I 5.0
Modes,
Key
Actions,
and
InpLt
Parameters
Maneu'yering between the various
EREPS
2.0
program
or performing actions
within a mode
special
an edit key, or a mouse button.
function key,
modes
is accomplished by pressing a Labels
for
the special function keys, Fl through F10, are displayed at the bottom of the screen. Special function keys which are not applicable to a particular mode are not displayed. While special function key
labels
use will become An attempt has
are
been made
numbering
assignments
some
however,
cases
careful
to a great
clearer as to
therefore
familiarity with
retain
between
this
extent self-explanatory, their
you gain
was
all
not
to
read the
of
the
common the
special
EREPS
always
the
2.0
function
key
programs.
In
possible.
labels prior
program.
You
to pressing
1ust
be
a special
function key.
i
A
3 *
special
summary function
description of
5.1
EREPS
edit
used
to
COLORS
mode
enhance
the
give
may
a
keys
a
and
input parameters
reference
mouse
list
buttons,
of
all
and
a
follows.
Each
particular
EREPS programs except
displays.
While
a
"palette"
color
letter
is
you
of
may
chnge
a
special
colors
letter the
colors
Therefore,
available
assigned
SDS,
and
color
of
were
Is
chosen
application the
from
by
color
COLORS
which
to
specifying
the
plot
a
axes,
You may exit the COLORS mode, make
changes permanent (by storing the color changes to the or temporary (until you exit the EREPS 2.0 program) hy
Spressing the bottom
the
appropriate
line
of
the
active special
screen.
COLORS
EGA and VGA systems.
1
2.0
impression, your
text, overlays, cursors, etc. color *.INI)
EREPS
a differing color assignment.
presents
choose.
In all
-
pleasing visual
require
mode
1
modes,
Mode Definitions
3 to
and
EREPS
61
function key display on
mode
is
available
only
for
I I I CROSSHAIR mode at
the
center
at
the
crosshair's
of
The
-
the
screen last
It
the
The crosshair
screen.
direction
by
lower-right the
beyond
at
arrow
of
a boundary,
crosshair.
not be
rightmost
crosshair at keys
of
the
the
previous
only when a graphic is
5 pixels
the horizontal. the
of
a mouse.
will
wrap
key will
the
is in
If
the
appear
is
the
place
place
key will
side
the
the
the
the
display.
crosshair at
the
is
top
the
moved
to
side.
move
in the
the
center
crosshair
key
of
in
opposite
The
and
positioned by
crosshair
place
to
vertical
abscissa
crosshair
to
call
displayed on the
The
crosshair
around
display.
leftmost
will
during
crosshair
to CROSSHAIR) or
screen. The crosshair
The
side
first
a
accomplished when using a mouse
The
the display.
display,
or
it
call
center
the
keys
(for the
displayed in
the
corner
Wrapping will
of
available
pixels
values
ordinate
using
5
displays
position
CROSSHAIR.
is
CROSSHAIR mode
at
the
will place
the
The
and bottom
I
and
of
the
respectively.
I
I EDIT
mode
entry/edit point, capabilities. 2.0
program's
screen.
data the
to page
value
Within
screen of
vary
feet, 1000,
data
within a field.
will will
be is
upon
displayed
called the
A field the
appear within appear within field
appear
adjacent
left
of
value
to
field.
(if each
upon
a page.
program
value units
primary
for the
the
The
and
data
field.
For
actual
The
value
the
unit
to
example,
a a
height,
say
height,
say
field
and
the
field
3
of
located upon
The unit of The
the
a unit field or
are appropriate
other with
computer's
quantity
is
it contains.
field.
EREPS
format of
the
of data
may be called
data
the unit the
the
data necessary
transmitter height.
will
the
any
as
may allow minor entry/edit
individual piece
depending upon
its associated unit
serves
other modes
will
Each
program input may be
mode
a mode,
depending
display.
field
EDIT
although
operation
Each
page will
The
-
I
3
value) to
the
I
i
I I I tab,
arrow,
then
fields,
title,
within
selected by
list
In
the
the
to deviate
from
The
item
is
are
pre-
them.
They
of choices
alternate control
complete
the
In addition, a default
through a list
have
You
if
able
no
to
item, an
the
units
cases,
over
screen.
allowable
not be
some
the
on
All
field.
mouse
cursor moves
units
possible
a
the new value,
title descripition of
of
"toggling"
bar.
As
using an
by
or
item, typing
the
valid responses.
will
possible.
be
will
a long
the
you
and
programmed
the
a
key,
space
prompt will appear
a range of
and
appear
may be
backspace,
change
for
selected
key.
consist of
abbreviated
will
the
informational
will
numeric,
tab,
be
flashing cursor over
pressing
an
prompt
reversc
the
position and
value may
unit or
A
of units
choice the
of
using
by
values
however, as you are allowed the option of overriding the recommended range of validity by simultaneously pressing and . Note! An entered value which is outside of the
3
valid range
may
abort
a
cause
with
yield
to
therefore,
error,
runtime
other
some
results,
erroneous
cause
to
exit
the
You
recommended limits
the
the
program
to
computer memory, or
of
consequence.
undesirable
adhere
loss
cause
are
encouraged
when changing a
value.
You
1
the
of
displayed on
bottom
FILE mode file
to a disk
3
or
delete
change
the
a
for
previously
or
list
filing operations
I
functions
are
in the
of the
FILE mode
future
directory
directories,
special
The
-
line
use, saved
which
the
to
pressing the
INIT mode,
or
by
data
pressing
through
FIO)
of
entered data
to save
previously
file.
files are
In
to be
stored
data,
addition, you may
stored,
create new
existing directories. pressing one
through F10)
63
(Fl
keys
allows you
retrieve
contents
(Fl
by
any
screen.
accomplished by
keys
time
at
function
special
active the
EDIT mode
return you
which will
key one
may
of
displayed at
the
These active
the bottom
of the screen.
Additional
screen prompts will
be provided as
needed. For PROPR, you may retrieve a file that was stored using EREPS
revision 1.0.
However, parameters not found but required
by EREPS 2.0 will assume EREPS retrieve In
a RAYS
addition,
the
the
it
mode
is
saved
name you
easily
adding
programs add
.DAT
the
is
EREPS
or
the
to
all
EREPS
mode
the
-
The
may
select
the
physical
appearance
the
mode,
display.
separate
mode
except
is
a display
nmi or km)
there The
described below.
are
of
the
file
names stored under data
data
3
directory
for
I 5
pressing
the
I
way
file
I
the
files may
other program files by Another
3
in
directory
of MS-DOS
any
time
return you
the
by to
to prevent
logical This
pressing type
the
mode the
no choices
on
the
SDS
key.
In
entry
that
control
not
have an
physical
starting point
reached
of data
does
for SDS
I
point
may be
or method
display.
INIT mode.
starting
and parameter values
the
logical
at
SDS.
a program by
(e.g.,
since
files.
INIT mode
set units
of
conventions
to file
key which will
programs,
you
a
stored
created.
within a directory,
the
FILE
and
INIT mode
be
if
saved
I
programs.
from any point within this
to
crate
INIT mode for
follow the
an extension
extension
You may exit EXIT key
it will
not be
that are
directories,
distinguished from executable or
a
of
exist,
When listing files
file confusion each
not
of results will
parameter values
When changing
2.0
do not
overlays
current
enter does
FILE mode. be
the
files.
naming and
You cannot
that
or previous
only
EREPS
default values.
was stored using EREPS revision 1.0. custom screen labeling you may have done under
any
LABEL
since
file
2.0
3
appearance is
its MAP
I
I
I i I Once are
are
considered the
session.
If
provided by as
may
program. Units
default units
2.0,
default be
Once
changed,
default use
active
the
bottom line
field
on
exit the
function
of
the
mode
-
modify
bottom line,
which
You
the
use
screen.
The
the
cursor the
next row
will
move
row.
key
to
if
down
and
the
in
the
left
3
will
throughtout until
any
use
the
entire
changed again.
by
pressing
by
the
F1O)
displayed
a mouse
both
column.
position past
left
keys
the
side
character
screen, except
the
left
(11, 81.
of the
will place
21,
The
column
31,
move
etc.)
or
screen and
the
the
character.
one
The
at
labels.
cursor.
current
key will
column
last
enter custom
function key
cursor The
to
any
to move
erase
the
you
the
special
at the
on
EDIT mode.
typing on
the
or by pressing one of
allows
anywhere
tab
time
through
placed in
move
to the
cursor
and the to key
down one
at
the
top
screen respectively.
-
W 4 thin
is
chosen,
center
of
the
of
for
function key.
Upon pressing
or
already
option
corner
(Fl
reserved for
next
the cursor
of
the defaults
saved
special
program,
legends
in that
the
LEGEND mode Error
EREPS
arrow keys
The
and bottom
is
character
right
be
program
function key will remain for
LABEL mode
and bar will
may
remain
at
the
keys
row/column positions
erase
3 3
terminate
normal
may
will
INIT mode
or
to
other than
a
pages
the special
labels
3The
I
they
page, you will be
LABEL
key
5
special
the
pressing
the
however.
key which will the
by
INIT mode, they
remainer of
you enter
on various
stored by pressing
future
from within the for the
the units
units
changed
You may
3
selected
you usually work with units
EREPS
future
Units
*
units
the
the
the
RAYS
program,
program will
65
Each
the
Altitude
display a color
screen with a crosshair legend box.
if
shown
colored
at
the
legend upper
segment of a ray
I
corresponds to the height difference, using the error increment specified, as compared to the same ray (equal launch angle) in a standard
atmosphere.
anywhere
on
the
LEGEND mode is LABEL mode,
In addition,
legend
may be
moved
screen by using the arrow keys or a mouse.
entered
the
the
from the
LABEL mode.
legend will disapper from the
The
Upon exiting the screen.
preclude later confusion with an overlay should
the
This will
legend also
contain as a background, a portion of a previous raytrace.
MAP mode - Within the SDS program's MAP mode, a world map with a superimposed 10 degree latitude by 10 degree longitude Marsden square grid is displayed on the screen. A Marsden square defines an area from which climatological data may be retrieved. A single Marsden square or combination of
I 3 3 3 ! I
3
squares may be selected (or a previously selected square unselected) by placing a crosshair, using the arrow keys or the mouse, within the square and pressing a special function key or a mouse button. For
a
reference, each selected square will be
3
of
color.
When all
the
highlighted by
a change
desired squares have been selected, pressing
or a special
function
key
will
produce
the
SDS
climatological summary display. You may exit the MAP mode by pressing the key whic, will exit the SDS program or perform other functions such as filing data by using the active special function keys displayed on the bottom line of the screen.
OPTIONS mode scale of the prompted
-
The OPTIONS mode allows you to change the
plot axes and other parameters
for
in INIT mode.
essentially
equivalent,
Prompts except
that were
initially
in OPTIONS and INIT mode are in
the
OPTIONS
mode,
previously created graphics display remains on the screen. operations such as changing display colors, resetting defaults,
etc.
any Other
EREPS
or exiting the OPTIONS mode may be accomplished by
pressing one of the active special function keys displayed on the bottom line of the screen.
66
I 3 I 3, 3 3 i
i
I 5
One special function key exception is the OVERLAY key. You may not change the vertical or horizontal scales of a graphics display and then overlay the new display upon the previous dislay.
Overlaying two graphics displays with differing
scales is not allowed.
SUMMARY mode
Within
-
the SDS program, the summary mode
is used to display the evaporation duct height histogram and the surface-based duct climatology. You may exit the SUMMARY mode by pressing Lhe MAP special function key or the key, both of
3
which will
1
5.2
return you
to
the MAP
Special Function Key Definitions The
special
function keys used within EREPS
CHANCE PERMANENT:
I
mode.
Active in COLORS mode.
any changes made to color definitions will be
2.0 are
When pressed,
stored in the *.INI
file for use as start-up defaults. CHANGE pressed,
any
THIS
changes
changed until you exit
3
SESSION: made the
to
Active color
in
COLORS
definitions
mode. will
When remain
program.
CHOOSE UPPER AIR: Allows
selection
Active when in summary display of SDS. of a single radiosonde station when multiple
stations are used for the summary of a given square. COLORS: COLORS mode
whereby color
COARSER: required. movements.
Active
It
is
in
OPTIONS
definitions
mode.
Places
may be
changed.
you in
the
Active whenever movement of a crosshair is used to increase the step size for arrow key
COARSER has no effect upon any mouse movements.
67
I I DELETE FILES:
Active
in the
FILE mode.
Allows deletion
of previously stored data files. EDIT:
Active in the
INIT mode.
Places you
in
the EDIT
mode whereby parameter values or units may be entered or changed. EXIT:
Exits
Active in all modes except INIT, COLORS, and EDIT. from current mode to previous mode. For instance, if you
enter the CROSSHAIR mode from the EDIT mode,
pressing EXIT will
3 1 3
return you to the EDIT mode. EXIT W/O CHANGE: COLORS mode,
Active
ignoring all
FILE: mode whereby
in the
COLORS mode.
Exits
the
color changes made.
Active in the
EDIT mode.
parameter values
may be
Places you in saved or
the
I
I
FILE
retrieved from
files. FINER: required. movements.
It
Active
is
used
whenever
to decrease
movement the
of
step
a crosshair
size
for
is
3
arrow key
FINER has no effect upon any mouse movements.
GET FILE:
Active
in
the FILE
and
MAP modes.
Allows
retrevial of previously stored data files. HELP: active special KEYS:
Active in all modes.
5
Displays definitions for all
function keys within the current mode. Active
display of special
in all
modes.
function key
It
is used
to
remove
the
5
labels from the bottom line
of the screen thereby allowing "clean" hardcopying for viewgraphs, etc. LABEL: display of SDS.
Active
in
the
EDIT
Places you in the
mode
and
in
the
summary
3
LABEL mode.
I
I I LEGEND:
Active
in
the
LABEL and LEGEND modes
when the altitude-error display option is chosen.
of RAYS
From the LABEL
mode, places you in the LEGEND mode.
5
LINE:
Active
in
the CROSSHAIR mode.
from a previously defined point to the Pressing
the
LINE key or
beginning point keys
or
a
rubberband or
the
line
will
cursor position.
right mouse button will
for a line.
mouse
right
the
current
Will draw a line
Moving
activate
a
the
signify the
cursor with
the
"rubberband" line.
arrow
After the
is positioned as desired, pressing the LINE key mouse
button will
draw
a
solid line
beginning to the ending point of the rubberband line.
from the The entire
process must be repeated to draw a subsequent line segment. LIST DIR: files
I
in
the
MAP mode
MARK: marker on the
the
FILE mode.
Active in the summary display
3selected.
5
in
Displays
a
list
of
current directory.
MAP: in the
Active
from which one or more
Active
in
the
of SDS.
Places you
Marsden squares may be
CROSSHAIR mode.
Draws
a small
screen at the crosshair's current position.
MOVE LEGEND:
Active
in
the
LEGEND mode.
Will display
the color legend at the cursor's current position. NEW DIR:
Active in the FILE mode.
Allows you to create
a new directory for data file storage.
3
OPTIONS: OPTIONS mode where
Active
in the
EDIT
mode.
Places you
in the
scaling and other display-oriented parameters
may be changed.
5
OVERLAY:
Active in
the
EDIT mode.
Superimposes a new
graphics display upon a previous graphics display.
I I
69
Note!
In the
I I COVER program, this function is not active when display option 1 is selected and more
PLOT: Clears
the
and want of
current
current
the
the
Active
Note!
graphic.
graphic
input the
INIT,
EDIT,
from the
and
OPTIONS
screen and
old parameter, use
the
change
modes.
displays
a new
graphics
for
a parameter
If you change
parameters.
effects of
compared with
I
those
I
the Overlay key.
square
a Marsden
Unselects
in MAP mode.
Active
given.
key will only display the
of
to observe
world map.
the
to
in the
Active
RESET: values
the
plot
REMOVE: from
in
The
set
threshold is
than one
the
EREPS'
OPTIONS
default
values
mode.
Resets
and places
all
you
in
current the
EDIT
mode.
SAVE FILE: to store
data
to a data
Marsden
square
of
Allows you
FILE and MAP modes.
file.
the MAP mode.
in
Active
SELECT:
in the
Active
interest
for
Allows
retrieving
you to
specify a
climatological
3 I
information. SET DEFAULT: height and range in subsequent
Active
units
in the INIT mode.
the
to
*.INI
file
for
Saves the current
use
as default units
program use.
Active
SUMMARY:
in
the
MAP
mode.
Displays
annual
1
in the
I
surface-duct summary from selected Marsden squares.
XHAIR: CROSSHAIR mode
Active such
that
in
the
EDIT mode.
graphics
Places
result values may be
you
digitized. i
70
I 5.3
Edit Key
The
I
Definitions
edit keys used within
Backspace
key
- Moves
within a field and enters
Ctrl *
to
insure
that
Del will
Enter
delete
the
the
present
field, If
the
will
cursor will
is
at
wrap
the
not enter
End key
of
the If
topmost
the
the
cursor the
right
a units
- Moves
to the
left
test
is performed
is within recommended limits.
RAYS program,
present
value value
field
cursor
to the
to its
the bottommost
to
space
level highlighted by the
position.
cursor will move
the cursor
cursor
I
field
one
Enter, except no
Moves
-
cursor
EDIT mode
environmental
Down arrow key its
as
the entered value
Within
-
the
2.0 are:
a blank character.
Same
-
EREPS
this
key
cursor.
next field below field
is
a
associated value
unit field.
field on
the
field
the page.
on
page,
the The
from above.
to the
last value
field on
the
page.
3
Enter key if it's field beep
3
limit
within acceptable
to
the
will
topmost
- Accepts
limits
right or below.
sound
line
the currently
and
of the
an
error
page.
and
moves
If a value
that
the cursor is not
to
or value the
next
within limits,
a
on
the
Ctrl Enter will override
the
message
Note
displayed unit
will
be
displayed
testing.
Esc
key
-
or MAP page,
moves
INIT
page.
or
5program
MAP will
When pressed the
cursor
When
from any page other to
pressed
terminate.
71
the from
the
INIT or MAP page,
the
value
field
INIT
on
first the
than the
I I I Home
- Moves
key
the
cursor
to the
first
value field
on
the page. Ins - Within the EDIT mode of the RAYS program, this key will allow you to insert an environmental level. A level line will be opened immediately above the current cursor position.
Left arrow key to
the
left
Moves
-
the cursor one character position
within a value field.
most position of a immediately
field, the
adjacent
to
If the cursor is in the left
cursor
the
left
will move
Mouse
May be
-
the
used
page.
to
value
field field
field above
if
the
MAP mode,
cursor
or
the
clicking the left
mouse button will select and the right mouse button will unselect a Marsden square. Within the CROSSHAIR mode, clicking the left mouse
button will
crosshair position key.
Within
draw a mark on
the
screen
The right mouse button will
the LEGEND mode, clicking the
at
the
current
enter
an
environmental level.
left mouse button will
Clicking the
right mouse
button will delete an environmental level. PgUp/PgDn keys - Changes the page displayed on the screen to
the
next
available,
or
previous
page.
If
no
1 3
simulate the LINE
draw the legend on the screen at the current crosshair position. Within the EDIT mode of the RAYS program when the environmental data is being entered graphically, clicking the left mouse button will
3 I
position
Within the
the
(generally the unit
associated with the value field) or to the the value has no associated unit.
crosshair on
to
3
additional
pages are
I 3 3 5
a beep will be heard.
Right arrow key
-
Moves
to the right within a field. position of field below.
the cursor one character position
If the cursor
is
in
the
rightmost
a field, then the cursor will move to the next value The
cursor will
not enter
a unit
left.
72
field
from
the
5
1
I
I Shift tab key left
or above.
Moves the cursor to the next field to the
-
This key may also be used to enter a unit field
from an associated value field.
3 3
Space bar blank.
For numeric
-
For fields which
choices,
such
as
km,
or
contain
nmi,
character values,
a limited number
or sm
for units
enters a
of specific
of range,
it
will
toggle between choices.
I
Tab key or below.
N
*
3 U 5 I
3
The cursor will not enter a unit field from the - Moves
Up arrov key above
I
Moves the cursor to the next field to the right
-
its
present field
topmost field on the page, value field on the page.
5.4
the cursor to the next value field
position.
If
the
cursor
is
at
the
the cursor will wrap to the bottommost
Input Parameter Definitions The following
order,
of short
values for all
is a reference
titles,
any
listing,
associated units,
in alphabetical and the default
input parameters within EREPS 2.0.
ABS HUM
-
absolute humidity.
(grams per cubic meter).
Units
are
fixed at g/m3
Value must be z 0 and : 12.
Default
is
7.5. ALT ERROR
display
-
produce
is available
an
only for
VGA card and 64
kilobytes
(yes) or N (no).
Default
altitude
error display.
This
computers equipped with an EGA or
or more is N.
I
I I
left.
73
of memory.
Value must
be
Y
I I I ANGLE UNITS angle.
The
Default
is
GN
(decibel
Default
is
degs
over
32
for
isotropic).
transmitter
-
for
antenna
:
be
:
100.
pattern
type.
0
and
COVER.
radiation
1.
OMNI
I 3
2.
SINX/X
(sin(x)/X)
3.
CSC-SQ
(cosecant-squared)
4.
HT-FIN
(generic height-finder)
5.
GAUSS
(omnidirectional)
may
not be
3 or
4 in PROPR/PROPH
SINX/X
CLTR calculations. chosen
in
Default
used for
-
or
or
radar
applications
display option
of
appears
prompt PROPH.
Value
OMNI
(i.e.
otherwise.
display options
2 in COVER).
clutter
model
be
use
within
display option 4 is
only if
may
to
U 5
AVERAGE
or
BOUNDS.
is AVERAGE.
from
clutter
model
the Georgia
incorporated
Institute
model, modified by NOSC
to
thought
within ±5
to
be accurate
of AVERAGE
BOUNDS
and
radar applications
type
This
PROPR
The taken
for
TYPE
3
(Gaussian)
OMNI
that
21
must
fixed at
are
are
is
lines)
starting
(milliradians).
Units
gain.
Value
PROPR and PROPH,
Default
value
with raytrace
(degrees) or mrads
antenna
transmitter
-
ANT TYPE Values
may be
associated
mrads.
ANT dBi
value
units
-
will
will
display
representing
may be
present
lower the
for
COMP PW - radar (milliseconds),
us
the
and
for
average
and
(GIT)
ducting
dB within
upper
minimum
PROPR
of Technology
account
display
in
is
clutter and
is
radar horizon.
A
clutter.
and maximum
sea
effects,
the
clutter
PROPH
bounds amount
A
value (2
of
5
of
dashed clutter
U
a given range or height.
compressed pulse
(microseconds),
74I
width. ns
U its
may
be
ms
(nanoseconds),
or
ps
3
I I I (picoseconds).
Value
must be
0.1
and :
9,999.
Default
is
1.3
us.
dB BOTTOM
for
must
the be
is
the
It
the
dB values are default
I
default
for
the
to 10 units
- the
and :
i -200
ratio
noise
plotted
are
If
For
at
dB.
display
o;
Normally, the
dB
the bottom on
the
the
bottom the
graphic
top
of
by
and bottom
the
ordinate
top.
propagation
the
top
of
fixed at
loss,
Units
5
the
300. the
default
default
is
propagation
It
is
at
factor,
the ordinate
dB.
is
propagation
the
are
For display of
signal-to-noiRe
reversing
80.
reverse
loss,
Units
graphic product.
with
abscissa.
to
than
at
appear
ratio,
factor,
fixed
increasing and propagation
the
appear
to
and
at
the propagatinn
-
signal-to-noise PROPH
or
vertical
or for
Value must be
300.
dB LEFT
the
are
Note!
and bottom.
different
to
of the
decreasing toward
propagation
ratio
is
20.
loss
dB value
PROPR graphic product.
-200
is
ratio
top
Units
default
possible however
equal,
signal-to-noise
or
is
entries
dB TOP
-
the
signal-to-noise
the
factor,
For display of propagation loss
plotted with propagation or
reversing
the
the
at
product.
300.
ratio,
factor,
ordinate.
will
appear
and :
-200
signal-to-noise
factor
left
propagation loss
80.
For
display
Note!
Normally,
loss
increasing
and
possible
equal,
the
dB.
20.
ratio
decreasing however
dB value
factor,
of the
fixed at
to
at
of the
or
abscissa
for
Value m,'st be or signal-topropagation dB
scale
propagatioi the
left
reverse
the
graphic
the
is
factor
toward
the entries for left and right.
dB values are
5
bottom
PROPR graphic
scale
I
to
ordinate
propagation
3
propagation
ratio
or
3
propagation loss,
signal-to-noise
Value
3
the
-
on
the by
If the left and right left
of the
abscissa
will default tu 10 units different than the top. dB RIGHT signal-to-noise
1
-
the propagation loss,
ratio
to appear
at
75
the
propagation factor, right of
the
abscissa
or for
I I I the
PROPH graphic product.
Units are
fixed at
dB.
Value must be
-200 and 5 300.
DET FAC Value must
detectability factor.
-
be 2
-25
and
DISPLAY OPTION
25.
Default
Units is
are
fixed
at
dB.
0.
I
-
For COVER the display options are 1.
3
HEIGHT versus
RANGE coverage with up
3
to 4
user-defined thresholds. 2.
HEIGHT versus based
Default
For
RANGE coverage with
on radar
is
1.
range
versus
user-defined
versus
based on
on
Display
pattern propagation with up
or height
loss
range or
Display propagation
based
or
are
to four
3
or pattern propagation
height with
one
threshold
ESM parameters.
factor versus
4.
display options
thresholds.
Display propagation factor
3.
the
Display propagation loss factot
2.
threshold
parameters.
PROPR and PROPH,
1.
one
loss
range oi
or pattern propagation
height with one
threshold
3
radar parameters. radar
signal-to-noise
versus
range
or
height. Default
is
DUCT BTM 2
of
less
the
RAYS
than
that
DUCT of a
the 0 and
I.
the bottom of a duct
-
program.
Units
specified
with DUCT TOP.
TOP
-
the
RAYS program. < the
maximum
top
may be
of a duct
Units graphic
may be
ft
height.
specified by
ft
or
m.
The
The value must be
default
specified by or The
m.
Enter method
The
default
is
0.
Enter method 2 value is
must
1,000
be
5 3 5
ft.
I
ELEV ANG - transmitter
may be
degs or mrads.
and 200.
3
antenna elevation
Value must be
angle.
Units
-10 and : 10 degs or
-200
Default is 0 degs.
Enter method
For the RAYS program, the environmental
-
input methods are 1.
Numerical/Graphical height-refractivity This
method
allows you to
input
levels.
an environmental
profile numerically and/or graphically in height and refractivity levels. The default atmosphere obtained by this method is one with a standard
2.
gradient of 118 M-units/km. Refractivity profile characteristics. method enables top
layer
atmospheric
3
default
The
to
two
their height,
and relationship
a duct with
and thickness
in addition
layers.
described by
The
to describe
and bottom height
trapping
3
you
two
from
to
1,000
gradient calculated to produce
3
layer from
a gradient of
60 M/kft;
layer
a gradient of Pressure,
15
from
millibars
temperature,
humidity
(mbs), (%),
versus height default with
I
and an
17,000
M-unit
an elevated 10,000
feet with
elevated super-
and humidity.
to enter
levels (C
or
from which an M-unit profile will be
feet with
1.
7 77
of
Using this
of pressure F),
118
this
in
and
or N-unit
calculated.
obtained by
a standard gradient is
same
to 18,000
temperature
atmosphere
Default method
9,000 to
is
feet with a
the
feet;
method
duct formed by
M/kft.
method enables you
3
as at 0
subrefractive
refractive
3.
this
a trapping layer
feet
are
entered duct.
atmosphere obtained by
1,000
layers
refractivity gradient,
foot surface-based
at
its
additional
one with a 1,000
value
of
its
additional
to any previously
900
Using this
method
M-units/km.
The is
one
I I I prompt
ENVIRO
@ RANGE
for
operator
an
specifications environment
of
will
file name will be
ERROR scale
of
Value
must
500
is
stored
screen
RPE
will
error
and
<
its
not
multiple
allow
own
disk
initial
a
Each
file.
If
environmental
label.
display.
2,000
and
a function of range.
as RPE, the this
label
altitude-error increment.
-
1
a
within
specified
altitude
be
is
input.
listed under
INCR
the
This
-
environment as be
Propagation model
0
ft
or
Units
Defines
the color
may
ft
1 and 1,000
be m.
or
Default
is
3 ESM
SENS
fixed at
be
3 3
m.
ft.
are
U
-200
dBm
and
ESM
-
antenna
and receiver
(decibel referred 0.
EVD HT
Default is
to
1 milliwatt).
Units
Value
must
-80.
evaporation duct height.
Value must be
sensitivity.
Units may
be
ft
or
m.
3
s 40 meters or 0 and 130 feet. Default is 0
0 and
m. FREE-SPACE RANCE/dB THRESHOLD threshold
either
parameters, thresholds
or
specified directly, calculated
may be
specified.
For
PROPR and
the
dB value must be between
value 180.
must The
Default
GHz
are
within
calculated
ESM
Units
-200
may
5 400
-
and
0,
0,
display
PROPR
and
and
the
from
parameters. be
range value must
100,
SPACE REF
line
be
300.
nmi,
Up
km,
sm,
t 0 and For
dB value
radar
to
COVER,
four
or
dB.
99,999
and
the
must be
range
0 and
5
I
and 0 nmi.
the
free-space
PROPH.
3
propagation loss
Value
must
may be
MHz
be
Y
or
N.
is Y.
FREQ or
the
L 0 and
defaults
FREE reference
PROPH,
be
from
a system's performance
-
-
transmit
(gigahertz).
frequency.
Value must be
Units . 100
and s
(megahertz)
20,000
MHz
or
3
0.1
7
I I I and
5
20 GHz.
Default
is
5,600 MHz
for
PROPR
and
PROPH,
425
MHz
for COVER.
H
relative humidity for environmental
-
Enter method 3 of
RAYS. Units are fixed at percent. Value must be ? 0 and 5 100. Within the atmosphere, a relative humidity of 0 is not a natural occurrence. applicable provided is
I
80%
By
to
specifying
optical
average
percent
refraction.
which define
at a pressure
0
Two
however,
RAYS
arbitrary
defaults
a standard refractive gradient.
of
1013.2 millibars.
tropopause pressure of
250
The
will
second
be are
The
first
8%
at an
is
millibars.
HEIGHT UNITS - For PROPR, PROPH, and COVER, the value may be
5
ft,
m,
kft
ft or m.
the
units of height
default
BW
ft.
This
or environmental
Default
is
1.5
degs
for
5
For
input
for other values
Value must be > 0 and
will
such as
the
serve
as
transmitter
inputs.
beamwidth. 360
PROPR
RAYS,
degs
and
Units may be
or
PROPH,
0
and 6,283
11
degs
for
COVER.
HORIZONTAL horizontal axis
AXIS
INTEG
TYPE
calculations (incoherent)
3
K <
5.
-
LYR Enter method
of
or C
-
type
radar
is
BTK 2 of
1.333
-
the
quantity
Value may
of
signal
free-space Default
radius
range. is
the dB
program.
79
Value
used
may
in
be
I
I.
factor.
(a standard 4/3's
RAYS
on
PROPAGATION LOSS
integration model
the bottom altitude the
be
displayed
Default is PROPAGATION LOSS dB.
(coherent).
effective earth
Default
-
of a graphic.
or PROPAGATION FACTOR dB.
1
(kilometers).
transmitter horizontal
-
or mrads.
mrads.
km
Default is
height, receiver height,
degs
a
or
value may be
HOR
3
(kilofeet),
Value must be
> I and
earth).
of
Units
a layer as may
be
ft
defined with or
m.
The
i i I value
must be
greater
than
or
equal
to any lower layer or duct
top; less than any above layer or duct bottom; and less than its own layer top. The default is 9,000 and 17,000 ft for the first
I
and second layer respectively. LYR GRD
- the
gradient
of
refractivity
or modified
refractivity used within layers as defined with Enter method 2 of the RAYS program. Units may be N/kft, N/km, M/kft, or M/km. The value must be those defined within table 1. The default for a subrefractive, 60 M/kft,
standard, superrefractive,
and trapping layer is
35.9 M/kft, 15 M/kft, and -10 M/kft respectively.
LYR THK
the
-
thickness
of
the
trapping
layer used to
create a duct as defined with Enter method 2 of the RAYS program. The
units may be
ft
or
m.
The value may range
not including the height of DUCT TOP. LYR TOP
-
the
less
than or
greater than any lower own bottom.
The
to but
The default is 100 ft.
top height of a layer as defined with Enter
method 2 of the RAYS program. must be
from 0 up
equal
Units may be to
or m.
The
value
3
any higher layer or duct bottom;
layer or
default is
ft
i
duct
10,000
top;
and greater
than
and 18,000 ft for the
its
first
and second layers respectively. LYR TYPE - the type of refractive gradient used within layers as defined with Enter method 2 of the RAYS program. The value must be T ( t r app ing) , P (superrefractive) , B (subrefractive), or S (standard). The default is B and P for the first
and second layers respectively. MAX ANG
-
transmitting antenna's maximum elevation angle.
Units may be degs or mrads. -99 and 99 mrads. MAX
m, kft,
HEIGHT
or km.
Value must be ? -10
and 5 10 degs or
Default is 10. -
maximum
graphics height.
Units may be
ft,
For COVER, the value must be > 0 and : 99,999 ft,
80
3
U I 5
I I I 3
25,000 m, RAYS,
100 kft,
25
9,999.
<
km
with a default of 50,000 ft.
t 100 and :
the value must be
with a default and
and
of 20,000
ft.
50,000 ft or 30 and
For
scale to present a reasonable display.
km,
or
sm.
default of with
3
200 nmi.
If a value
the
For RAYS,
200
nmi.
of 0
-
be
ft,
m,
3
and s 5,000
value must be
graphic
will
2 0 and
self-scale
Default is 0.
Value must be 2 -10 and : 10 degs or is -2 degs or -10 mrads, depending
minimum
-
kft,
MIN RANGE
maximum range.
2 10
500 with a
transmitting antenna's minimum elevation angle.
or
-
sm.
graphics
km.
specified maximum height.
be nmi, km, or
10 and :
be nmi,
selected in Angle unit above.
MIN HEIGHT may
Units may
the value must be
entered, the
Units may be degs or mrads. -99 and 99 mrads. Default upon the units
range.
For PROPR the
is
The
height
value
The default
for
must
be
PROPH.
Units
2
s
0
and
minimum graphics range for PROPR. The value must be 2 0 and : the
Units may specified
The default is 0.
displayed within
value must be
3
NO. graphic.
the
5 10 with
1 and
optical region.
a default
I and
OF RAYS
of
100 with
-
6.
number
of
For
rays
The value must be 1 1 and : 300.
I 81
lobes
For COVER, the value must PROPR
a default of
I
I
the
is 0 ft.
NO. OF LOBES - number of constructive interference be
self-
The default is 0.
must be 2
value
to present a reasonable display. MIN ANG
3
maximum graphics
-
For COVER
a default of
1,000.
30,000 m
PROPH, the value must be 2 0
If a value of 0 is entered, the graphic will
NAX RANGE M
For
to
and
PROPH,
the
2.
draw
Default
on is
the 50.
RAYS
NSUBS
surface refractivity.
-
The value must be a 0 and : 450.
The units are fixed
to N.
Default is the world average of
I I I 3
339. P
pressure
-
Units are fixed >
250.
for
at mbs
environmental
(millibars).
Value must
be : 1100 and
Two standard atmosphere defaults are provided.
is a world average earth's
surface pressure of
second is 250 mbs which is an average P WIDTH ns,
Enter method 3 of RAYS.
or
ps.
Value
must be
and :
0.1
1013.2 mbs.
The
tropopause pressure.
transmitter pulse width.
-
The first
Units may be
9,999.
Default
ms,
us,
is 1.3
us
I
5 3 3
for PROPR and PROPH, 60 us for COVER.
PD 0.9.
Default
PFA _
12
x 10
probability of
-
and -1 2
!
is
0.9
2 (e.g.,
PK
PROPR and
probability of
-
and
for
detection.
POW
(milliwatts),
-
W
PROPH,
false
Default
(watts),
kW
peak
power.
(kilowatts),
t 0.1 and :
Value must be
Z 0.1
and
I
COVER.
Value
must
be
between
1
8.
(decibels referred to 1 milliwatt), Watt).
for
false alarm must be
is
transmitter
0.5
alarm exponent.
probability of
1 x 10 2).
Value must be
Units
MW
may
be
(megawatts),
mW dBm
or dBW (decibel referred to 1 10,000.
Default is 285 kW for
PROPR and PROPH, 200 kW for COVER. POLARIZATION are
HOR
-
transmitter antenna
(horizontal), VER
(vertical),
or
polarization.
Values
(circular).
Default
CIR
3 3 3 3
is HOR. PRF (Hertz) Default
or
-
pulse kHz
repetition
(kilohertz).
frequency. Value
is 650 Hz for PROPR and PROPH,
must
Units be
may
: I and
300 Hz for COVER.
be
Hz
I
s 9999. I
8
I
5
PROPAGATION NODEL
electromagnetic
-
model used to generate the graphic.
wave
Value may be
propagation
INTERNAL for
the EREPS models or RPE model.
When RPE
for NOSC's Radio Parabolic Equation (RPE) selected, propagation loss is read from
is
previouly-stored files generated by the NOSC RPE program.
I
EREPS 2.0 does
not contain
4.1.)
is
Default
-
PULSES
the
RPE
program.
Refer
to
(Note. section
INTERNAL.
number
integration model.
of
pulses
to integrate within
Value must be 2
1 and
the
99,999.
<
signal
Default
is
10.
RADAR technique.
CALCS
Value
may
(detectability).
3
pulse
radars
selecting
S,
use
must
must
enter
or
noise
ratio
3probability sM.
the
of
false
-
nuiber
of
pulses
integration
for
alarm.
a given
range axis,
-
to
is used. i.e.,
D
for rotating
Default
By
By
selecting
integrate By
the
and
selecting D,
if you
minimum signal-to-
probability
of
detection
and
is S.
receiver/target range.
AXIS
or
integration.
pulse repetition frequency.
Value must be 2 1 and : 10,000. RANGE
mainly
pulse
integrated will
detectability factor,
required
RANGE
calculation is used
of pulses
calculation
scan rate
incoherent
enter the
range
(integration),
calculated
transmitter's
you
I
be
and
coherent
(simple),
horizontal beamwidth and horizontal
antenna's
I,
S
free-space
noncoherent
number
from the the
be
Simple
that the
radar
-
Units may be
nmi,
km, or
Default is 50 nmi.
For COVER, determines
the
appearance
either as a flat or curved earth graphic.
curved-earth display, the radius of curvature
of
the
For a
is dependent on the
earth's radius times the standard effective earth's radius factor of 4/3.
I !8
Value may be
F (flat)
or C (curved).
Default is C.
I 3 I RANGE UNITS
km,
nmi,
or
of
-
must
be > 0 and :
a
(decibels above
or dBsm
(square meters)
sqm or z
99,999
and : 50 dBsm.
-30
be
sqm
Value
meter).
square
I
range.
may
Units
section.
cross
radar
target's
for
range
other values such as maximum graphics range or free-space RCS
is
Default
sm.
default unit
the
serve as
input will
This
nmi.
may be
units
-
1
I
at dB.
I
is
Default
sqm.
REC NF Value must be 5 for
t 0 and :
or
kft,
1 and
RAYS
within the
is
(no)
field.
environmental
the
-
may
be
Default
Value
screen.
computer
value
corresponding
to
each
every
screen
will
be
uninterpolated data will the
display is
specified faster
in a courser
than that mesh
ERROR
symbols
N/A
will
screen
appear
PIXEL, number
used for
to be
or
RPE
M-
data
output
PIXEL
or
FILE.
interpolated
to
produce
pixel. By
Using
3 3 3
specifying
While
for RPE
this
By a
FILE,
location
method
of
files which contain
of pixels
on
the
I 5
method,
this
its proper pixel
resolution.
than the
Y,
is M-units.
activated.
of
RAYS is
(refractivity)
must be
be plotted at
graphics
the
ALT
displaying
data will be
RPE
pixel
of
3 n
If
N-units
3
I and 30 kft,
ft,
30 ft.
is
(yes). the
ft,
is Y.
method
specifying PIXEL, the
data
Units
Units of refractivity
-
(modified refractivity).
the
Y
Value may be
input.
RESOLUTION
under
PROPH,
reflected rays within
and
Default
REFRACTIVITY UNITS
upon
and
30,000
<
Default
or
applicable
not
input
3 and
display
-
be N
Value may
entry
must be
1 and 10 km.
or
10,000 m,
graphics.
units
PROPR
for
- receiver/target height.
Value
km.
REFLECTED
this
14
fixed
COVER.
REC/TRGT HT m,
is
Default
100.
Units are
figure.
noise
- receiver
3
screen, a
8 84
3 I I "spotty" display may result since not every screen pixel will be *
activated. SBD HT M.
surface-based duct height.
Value must be a 0 and
is
Units
are
1 and
transmitter's
fixed at 9,999.
s
Default is
SMOOTHNESS of milliradians ray
trace.
Default
antenna horizontal
ray
-
smoothness factor.
angular
Value must be
15 for PROPR and PROPH, 6 for COVER.
incremented at each new
Using
scan rate.
This
angle
increments
in
is the number
performing the
allows you
to vary the
appearance of the
rays by adjusting the smoothness factor,
small
making the
that
increments the
smaller
increments and, the be
M.
rays
appear very
rays appear more jagged.
the
smoothness factor, the
therefore,
You
The value
meters.
3
must
smaller the angular
0 and
5 30,000
-
(steady) or I-FLCT
Swirling case number. (slowly fluctuating).
SYS LOSS - system losses Units
are
fixed at dB.
8.4 for PROPR and PROPH, TEMPERATURE environmental input. Default
The value must
Units may be ft or
feet or
0
and
10,000
be
0-STDY
Default is 0. SW CASE
I
be
should note
the greater the time needed to perform
radiosonde launch height.
-
i.e.,
smooth and large
ray trace. Units are fixed at milliradians. 0.1 and 5 10. Default is 3. SONDE HT
3
ft.
rpm (revolutions per minute).
increments making the
3 3
1,000 m or 0 and 3,000
s
0 m.
SCAN RT
3 3
Units may be ft or
such
as
Value may
Default is l-FLCT. line,
beamshape,
Value must be > 0 and 5 100.
etc.
Default is
6 for COVER. UNITS
-
Units
of
temperature
for
Value may be C (Celsius) or F (Fahrenheit).
is C.
85
TNP - temperature for RAYS. and
Units may be
: -1100
C or
and : 1250
provided.
The
F.
F.
is
a
world
temperature
of
reduced with
a standard atmospheric
pressure of
The
second
average is
-520
lapse
5 5 ' C,
-800 and
defaults
earth's
C,
which
rate of
3 of 0
surface is
-6.50
are
150
C
C/km to a
millibars.
3
TRAN/RADR HT - transmitter/radar height. Units may be ft i and 100 m. ft or 250 5 Value for COVER must be > 3 and
or m. The
250
C.
must be *
Value
Two standard atmosphere
first
150
Enter method
environmental
I I I 3
default is
100
ft.
and : 300 ft or 1 and must be
Values for
00 m.
PROPR and PROPH must be
Default is
7j
ft.
Value
3 and s 50,000 feet or 1 and 30,000 meters.
3
for RAYS
3
Default is
100 feet.. VER or mrads.
BW
-
antenna
Value must be
Default is 10 degs
vertical beamwidth. : 0.5
of
the
45 degs
or
may be
9 and
785
degs
mrads.
for PROPR and PROPH, 19 degs for COVER.
VERTICAL AXIS - the axis
and :
Units
graphic.
quantity displayed on
This
prompt
is
active
the
vertical
only when
PROPR
Value may be PROPAGATION LOSS Display option is 1, 2, or 3. or PROPAGATION FACTOR dB. Default is PROPAGATION LOSS dB. WIND DIR be degs
or rads
and 2 rads.
WIND
-
wind direction relative to upwind.
(radians).
Default
SP
-
is
wind
(meters/second), mph Default
* 0 and :
dB
I
Units may
180 degs
or
0
0 degs.
speed.
Units
(miles per hour),
Value must be 2 0 and : 100 and 99 km/h.
Value must be
I
may be kts
(knots),
m/s
I
or km/h (kilometers/hour).
kts, 0 and 50 m/s, 0 and 99 mph, or 0
is 10 kts.
I
I
I 6.0
Limitations
EREPS
I
The
limitations of the
a.
Frequency:
are
EREPS programs
to 20 GHz
100 MHz
as
follows:
PROPR, PROPH,
in
COVER
and FFACTR.
b.
I
to
only
I
over-water
justified at
is
should
be
only
Optical the
used
null
Evaporation
f. single-mode
of
radius
valid
not
models
All It
the
for
assume
this
believed
is
a
described by
time,
as
(K):
The diffraction
to
factor
dependent upon K.
not
study
in
changes
the
may
locations
exceed
duct
height:
All
the
than
5 GHz,
14 meters at
10
and
GHz,
the
of
lobes
are
small-angle is
No check
programs
an evaporation
greater
duct
30 meters at lOm at
should give acceptable
18 GHz.
use
and
3 GHz,
a
may 22
Below 2
results for all ducts
meters.
Surface-based ducts:
a single-mode
region
1.33.
in error.
to be
Variations
optical
number
large
duct heights
all programs
g.
angles
a
for
error
meters at
If
of propagation for
model
between 0 and 40
*
are
apply
these large angles.
made by the programs for
GHz,
models
85%
region:
elevation
causing
assumptions,
5
models
Otherwise K should be kept at a value near
requested,
in
FFACTR
least
earth
Effective
e.
be
and
atmosphere.
and evaporation duct models are
nulls.
COVER,
of
(1985).
d.
K
exception
homogeneity:
homogeneous
horizontally
in
single
The
paths.
Horizontal
c.
limitation
the
paths.
terrestrial
Hitney
PROPR, PROPH,
the
troposcatter,
With
paths:
Over-water
empirical
model
to
87
All programs, approximate
except RAYS,
use
surface-based duct
I I I propagation which
is best used to illustrate the skip zone effect
This surface-based duct is one created and range extensions. from an elevated trapping layer and not from a surface-based trapping
layer
(see
section
2.4.3).
refractivity profile would have solution program in order to beyond the scope of the h.
Model
approximation to approximatiorn
achieve accurate
vertical
3
results,
this
is
EREPS programs.
geometric
assumes
exact
to be provided to a full-wave-
approximations: the
An
that
COVER uses
a parallel
ray
model given in section 7.1. The
the
direct
and
sea-reflected rays
This assumption arrive nearly parallel at the receiver/target. is quite good at long ranges and higher heights. However, as ranges and heights decrease COVER program will be
in error, with the error becoming worse
ranges and heights decrease. make
the parallel
program
the assumption becomes poorer and the as
The PROPR and PROPH programs do not
ray assumption.
are suspect,
If
the
results
of
the
CO'
R
they may be compared to those obtained from
PROPR or PROPH. i.
Graphics
i shading
routines:
As
the
frequency
or
antenna height Increase, the lobe spacing as shown by figure 13, decreases. For some cases of the COVFR program, the spacing may become
so small that the graphic
will fail.
For these cases,
by increasing
i
routine used to shade
the shading problem may be
the scale and replotting the graphic.
the
lobes
corrected
3 3 II [
88
3
I 7.0
EREPS Models
U
The
various
described below RAYS,
5
and
FFACTR
implemented
each model
I I
7.1
5
3
are
of
speed
somewhat
EREPS
through 7.5.
based on
these
and graphics differently.
programs
PROPR, models;
are
PROPH, COVER, however,
for
presentation, each program The
implementations
for
Propagation Models
the
transmission
in
free
from
the
the
simplest of
space.
properties
are
a
vary,
from the
i.e.,
the no
distributed
over
level
any
along
the
sphere's
The
power
space,
Pa
of
space
a
is
transmitter
the
and
defined
homogeneous, earth's
wave
total
front
amount
losses an one
to
ever ray
radius.
"
and
as
a
spreads
receiver
region
loss-free,
atmosphere.
a
In
whose
i.e., free
uniformly
away space,
in
energy
ali
decreases is
),
transmitted does
absorption,
enlarging
This (W/m
of
surface.
a
the Thus
the
free-space
sphere
at
not
energy the
inversely with the
called over
etc.,
is
energy
square of
path-loss.
any point
in free-
t 4w
the
between
is
transmitter.
density,
5 P
wave
wave propagation
is
Pa
where
of electromagnetic
isotropic,
electromagnetic
While
case
Free
influences
directions
is
all
the
are briefly described in Section 7.6.
The
3
underlying
in section 7.1
considerations is
models
is
the
radius
of
power the
(
6)
r2
radiated by sphere
the
in meters.
89
transmitter
in Watts
and
r
I I I In
free
space,
times
sphere's
surface
receiver
antenna,
Ae .
The effective
also
area
the
the
called is
aperture
the
of
sphere
antenna's
related
at
a
loss-free,
density over
the power
is
receiving antenna
isotropic
density
power
the
to
the
the
covered
entire by
I
the
effective aperture, wavelength
(A)
of
radiation by
A
G A2
-
I
7)
Ae
where
is
G
antenna, G
Pr
the
Thus
is
unity.
-
P a A e2 -
For
gain.
antenna's
power at
the
a
loss-free,
the
receiver,
PtA 2 (4
isotropic Pr
is
(
8) I
7rr )
I
The free-space path loss is expressed as
2
(4r)
Pt
L
P2r
A
where r and A are in the same
units.
9)
2
I
The
free-space
path
loss I
expressed in terms of frequency is
Lfs
for
32.44
r in kilometers
+ 20LOG 1 0 (r)
and
4
+ 20LOG 1
0
(f)
(10)
I
I
f in MHz
I 90
U I I If
non-isotropic
considered within
the
antenna
radiational
loss calculations, the
as propagation loss rather than path loss. can be
to
the ratio
of the actual strength that
5
I
directed toward the point in question.
the
field
under free-space
F
3
with the
beam of
is
at the same
an
( I1)
the magnitude of the electric
field under free-space
identifiable
such
effects
is a desirable
parameter in most
It contains
diffraction
quantity since
radar-detection-range
all the information necessary to
as
sea-surface
it
reflection, in the
account
atmospheric
atmosphere, and
from the bulge of the earth's surface.
Thus,
if the
functional form of F is known then the propagation loss at any point can be determined since the calculation of the free-space field
is
quite
simple.
antenna patterns,
L
-
There methods
for
propagation
I
investigated
point.
equations. for
transmitter
Symbolically this is
refraction, scattering from inhomogeneties
I
the
conditions and E is the magnitude of the field to be
is
3
at a point in at the same range
IEI IEo0
-
E0
conditions
The propagation factor
3
is refered to
The propagation loss
field strength would exist
space
where
loss
are
described with the aid of the propagation factor which is
defined as
3
patterns
I
L fs
are
is
-
The propagation
equivalent
(in
dB)
including
to
(12)
20LOG 1 0 (F)
three distinct regions which require different
obtaining loss)
loss
as
signal
strength
a function of range.
91
(or, The
equivalently, first region is
I I I called
the
extends the
optical
roughly
optical
which begins
obtained by
meters,
radio
horizon.
lies
between the
a
linear
the
all
interpolation
and
the
region
are
optical
in
between
third region,
this F
values
in
n
the
sum D,
EM
the
the
1
systems
all
and
heights
angles
in
are
in
the of
the
the
paths
as
ray
shown
will
difference
earth's
or radar
which arrive
reflected
3
radians n
operated near
field components
the
due is
to
the
path-length reflection
made
their
that
same
the
spatial
addition
following
absorption or
[f(e
models
kilometers,
sea-reflected
of
very nearly
in
in
the
field at a receiving antenna
and
assumption
factor
are
of
lag
surface,
target
is
the
at
that point via
in
figure 6.
the
phase
in path lengths.
The
of
The
3 3
the
total
$
3
e, of the reflected ray with respect to the direct ray
lag,
change,
F -
levels
U 3
region
Interference Region Models
component of
the
gives
s'gnal
A
The
stated otherwise.
direct path because
is
The
discussion ranges
sum of
direct
phase
surface-reflected waves.
the
region,
In
coherent
just beyond
region.
electric
phase
dominated by two-path
and
region
horizon.
diffraction/troposcatter
For naval
the
radio
the
Optical
vector
to the
This
is
specifically
7.1.1
the
is
region.
and diffraction regions.
In
unless
region
optical
transmitter
direct
intermediate
diffraction
optical
the
between
distinct
called the
from
or
region, propagation
interference other
interference,
is
expression
from
2
) D R)2
the
direct
6,
and
surface.
In
the for
the
such
that
phase difference. F in
the
absence
phase
EREPS
and sea-reflected
direction,
refractive effects
)2 + (f(f
difference,
rays
the have
the
major
Kerr
(1951)
of
I 3
abnormal
as
+ 2 D R f(c
92
1
) f(U
2
) COS(6)]
I /2
(13)
3
I I I The
f(ei)
and the
factors describe the
angles, ei.
divergence
are shown in figure 24.
into account the spherical nature of R is the reflection coeffici.L ;,f the
surface (the
and incident fields).
ratio of the magnitudes of the reflected F varies from maximum to minimum as the
total phase lag, 8, changes by
I
and can assume values between 0
and 2.
o-
i
I
Figure
24:
D is called the
factor and takes
the reflecting surface. reflecting
(normalized to 1) antenna pattern
Two
path
optical
interference
region.
I I I The values
expression
e such
of
than or equal angle
is
which
the
This
olim
-
to
given
earth
divergence
given by the
TAN
I[(.001
the
effective earth
is
defined
the
as The
calculated
by
optical the
evaporation duct
is
less
region
is
obtained by
01
grazing Scaled - 21
as
-
angle
(8 - 2n)
If
difference,
optical
all 6,
and
is
the
all
greater
(1966)
factor
becomes
invalid.
the
f is
the
wavelength the
the
reduced
the end
where
from
above
the
following
duct
of the
optical
first
optical
formula
I
quarter wavelength or
than
10.25 meters use
I
e
value.
except
between
I 3
(15)
the
greater
3
that
if the
,
at
ae
effective earth radius is
U
ae
scaled evaporation duct height.
the
region maximum
programs
frequency in MHz.
the
COVER,
the
direct and
path
length
reflected
rays
I
I
given by
6 -
at
(14)
(scaled) evaporation
e1 )
of e
3
in meters,
region limit
range
-
f)i
3
grazing
Russell
using the
value
and A is
in radians,
for
and
in height
the
evaporation duct heights the
6,
(.01957)/(k
optical
1 + (A/10.25)(2f
limit,
Reed
times
meters
finding
the
valid
or at which
region maximum range
10.25
represents
For
is
than
occurs
radius
not zero.
is
8lim
, is and
applicable
height
region peak
radius,
earth
is
expression
grazing angle,
the
by
A)/(2 7 a e)i/3
is
is
13
path-length difference,
limit
0
where
equation
a
is
k.
in
spherical
where
factor
the
F
to one-quarter wavelength,
equal
limit
that
for
2w
(2 H t , Hr ')/(1000
r A).
94I
(16)
I I I Here
r
is
the
antenna heights.
I
and Hr'
are shown
- H
(000
r- 2)/(2 a )
- Hr
(1000
r 22)/(2
and H r are
the
'
Hr' where H t
respectively. be
r1
ae)
transmitter and
and r 2
are
the
determined by solving
the
cubic
2 r13
r
+
I
Ht'
and Hr
'
This
equation
I
002
is
2 + (r
a
H
the effective
in figure
24 and are
r/2
-
(m),
(17)
(a),
C 18)
receiver/target
reflection point
can
.002 ae (Ht + Hr))r1
r
-
0
( 19)
.
also has
p COS((O
p [(4/3)(.001
the formal solution (Hr
+ x)/3),
a e(H t + H r) + (r/2) 212C21)
and
I I
r1
equation
where
I
ranges.
heights
frequently solved using a Newton-method
iterative technique, but
r-
3
'
given by
Ht
3
and Ht
ground range,
total
95
Ht)
(20)
I I 0 - COS_ 1 [(.002 ae (Hr - Ht)r)/p 3 ].
R,
and
phase shift, 0,
grazing angle, 0.
a
-
These angles,
.001(H r
-
.001 H t '/r
H t)/r
I
-
require
of
The the
in radians, are
r/(2 a e)
(23)
,
24)
,
-
r1 /ae
,
(25)
-
"7
p,
( 26)
in terms of quantities shown in figure can be
knowledge
24.
[I +
on
the
( 27)
(2 r I r 2 )/(r ae #)]/2
parallel.
assumption that
the
direct
The path-length difference
(4w/)
I I
I
For the COVER program only, the path-length difference is based
I
The divergence factor
calculated using the equation
D -
I
angular
about the angles a and 0 as shown in figure 24.
information magnitude,
require
f(ei),
antenna pattern factors,
The
(22)
and
reflected
rays
are
for this model is given by
1/2
[H 2 + 1000a (1000a + H t)
SIN2(#)
3 3
(28)
I 96I
where
i
[TAN 2(a)/9 + 2000Ht/(3ae)] 1 / 2
-
The grazing anglc
I
-
I I
and fi,
-
The
a + 7
-a
divergence
TAN(a)/3.
(29)
for the COVER program is calculated using
( 30)
,
the launch angle of
I
-
-
the reflected ray, is
equal to
(
2-y.
factor
is
given
in
terms
of
the
31)
quantities
of
equations 29 and 30 as
D
-
[1 + 2/SIN()
( 32)
/2
The parallel ray assumption simplifies the
determination of
the
cover contours since each contour is described by
U
r
I
- R fsF COS(a)
( 33)
,
for all angles a within the main beam of the antenna and greater than the Lower angular limit of the optical region. Here Rfs is the
free-space range
in kilometers.
97
I
I I I The magnitude as
calculated R,
and
the
of
a function 4?,
phase shift,
and vertical
RH
and phase
- 1
the
of
polarizations,
shift of
the
reflected ray
grazing angle 0.
the
reflected
respectively,
magnitude,
The
ray
for
can be
horizontal
are
,
0 H- W
where n and V
is
35)
n 2 SIN(b) - [n 2 n SIN(O) + [n 2
the
(complex)
indicate
circular
I
(34)
RiV
the
index
polarization
is
Cos 2 ]/2 COS ()] 1/2
of refraction and
polarization.
the
subscripts H
0C
The
.5[R
-
H
magnitude
roughness included Barrick
R - R
of
-
2
SIN'
of
the
in terms of
the
EXP(-2
using
([2
21/
+
2
the
i h
RvRH COS(O H
SIN($H +
reflected
reflecting the
I
horizontal
I
(Rv
the
following
(1971)
+ RH
I
for
and vertical coefficients
RC -
I
36)
The reflection coefficient
calculated
I
V)/(
ray
surface.
models of Ament
-
2
is
V)]I
2
( 37)
Rc)).
also
( 38)
affected by
Surface (1953),
the
roughness
Beard
(1961),
is and
formulas
SIN(O)I/
98
I
I )2
(h 0)/A
<
.110
,
(39)
I I -
R - R 0 (.5018913
I
R -
.15
.55819)2)1/2)
#)/A)
((h
-
(.2090248
.110 : (h 0)/A
:
.260
,
(40)
(h 0)/A
>
.26n
,
(41)
R
I where R 0 the wave
is
the
root-mean-squared wave height and height
Phillips
is
The
(Ws)
square
of of
polarizations
where
c
-
is
I I i
function
of wind
The
a
in
rms
speed using the
( 42)
the R
index and
cZ
of
refraction
for
required to make
vertical
and
circular
given by
are
the
conductivity, respectively,
function of
A the wavelength.
h is
model
e - i(18000 a)/f
and
frequency
a
a smooth surface,
in meters/see.
calculation
n
as
ocean-wave
for
.0051 W 2
-
for wind speed
*
obtained
(1966)
h
the
reflection coefficient
MHz.
The
ordinary
dielectric
of sea water, and f is
constants
frequency using
C 43)
,
Blake's
themselves (1970)
are
constant the
EM
and
system
obtained as
equations,
as
follows
a
i I I Case
1:
f
1500
-
80
( 44)
-
4.3
(
1500
<
a
Case
2:
a
Case
3:
80
3000
<
45)
f : 3000
0.00733(f
-
- 4.3
a
For
3
:
1500)
-
+ 0.00148(f
f :
-
69
-
6.52
frequencies
I I
( 46)
1500)
( 47)
I I
10000
0.00243(f
-
1
3000)
+ 0.001314(f
greater than
( 48)
( 49)
3000)
-
10,000
MHz
the
10,000 MHz values
in equation
13,
f(ci),
are
i
used. The
remaining terms
antenna
pattern
factors,
antenna
pattern
type,
are
determined
beamwidth,
and
as
a
the
normalized
function
pointing
of
angle.
the Five
difterent
antenna types are used in EREPS 2.0; omnidirectional, sin(x)/x, cosecant-squared, generic height-finder, and Gaussian beam. The simplest case is that of the omnidirectional antenna which,
as
directicnz.
The radiation
its
name
That
is,
implies, f(p)
has
- I for
second
case
is
pattern
of
this
the
a
all
gain
unity
in
all
angles p.
sin(x) /x
antenna
of
I
is
antenna symmetric
type. about
The
i
the
1
100
1
I I! (pointing) angle
elevation
3for
I
this
antenna
f(p)
- SIN(x)/x
given by Blake
f(p)
The
antenna.
the
(1970)
as
-
"max
> 0.03,
factor
pattern
-
'pmax'(
50)
(
51)
where
x
and
c
-
0.7071
1 0
A
when
3definition
of
c -
the
,
-
±
p
that
dBI
occur
the beamwidth
c
is is
BW
the
antenna
at p
-
of
chosen so
half-power
the antenna.
That
Angles
the
of
greater
±
0
Jmax
where A - w/x to
TAN
the usual
is
to
limited down
to
the
1 / 2
)
those -30
angles
dB
level
within (f(p)
than
(A / (1
are
limited
an
antenna
condition easily
(20
( 52)
are
antenna
-
This
points
which is
the
f(p)
beamwidth.
the
± BW/2,
p
that
1.39157/SIN(BW/2).
beam
equivalent
of
where
BW/2,
ensures -3
value
The
in
and maximum angle
the elevation angle
are
factor calculations
main
0.03).
-
(f(p))
IPattern
M
respectively.
normalization LOG
-
SIN(p
p max
and
;
main beam,
U
is
of
+ A)
to a pattern with
its
factor
of 0.03.
first sidelobes
achieved with modern antennas.
101
(53)
at
This -30
dB,
is a
I I I The
generic
the sin(x)/x beam upward the 1
direct
for
is
swept
an
values,
tapers
The
antenna pattern
e,
p,
for
the
p,
of
the
direct ray
the to
A fourth This
t
upward
gradually
antenna
is
a special case
of
antenna. Height-finder antennas typically sweep the in elevation. This can be simulated by subsituting
ray
all
height-finder
pattern
the
-30
antenna
pattern
factor
dB
type
is
not
elevation angle po" set.
As
for
the
factor
Then
the
f(p)
-
antenna beam
reflected
ray
level.
is
the
cosecant-squared
symmetric
about
the
:
antenna.
elevation angle.
is calculated using
f(')
-
I
Po
f(M)
-
SIN(BW)/SIN(p)
p
f(p)
-
[I
(o
-
-
I
p)/BWI
>
A
:
Ao
po
+
BW
f(p)
BW
+
( 54)
,
5 3
3
55)
( 56)
p < Mo
i 0.03,
I This
antenna
beam
antennas
pattern
the
the
-3
orientation of
be
used
an
airborne
that
for
the
angles then
radar
first
describe
always
dB, the
shipboard
below
antenna
different
since
coincide with The
is
are
or
the
of
half-power,
sin(x)/x this
or antenna
points is
of
the
Gaussian does
the one
not
5
antenna. that
would
radars.
Cosecant-squared antennas used on normally oriented in the reverse sense such
beam
to be
the
antenna given above
elevation
orientation
assumed
beamwidth
two equations the
from
is that
above angle
taper not of
would describe p.o
above
optional
The the in
third
the
a surface-based
ray
3
equation would
elevation EREPS,
direct
the
angle. antenna
The is
system.
1 102
I
I I I The final antenna option is the Gaussian beam antenna. The ?attern factor for this antenna is symmetric about the
I
pointing angle and is given by
- EXP[-W
f(p)
2
(P
p
-
f(p)
I
) 2/41 0.03,
-pmax : P :5 Amax
(57)
where
I
P
3
P
I
Ie
SIN(.)
-
(58)
- SIN( 0)
( 59)
W - (2 LOG e(2))
1
/2/SIN(BW/2)
(60)
,
3
and where the normalization factor W is chosen
I I
maximum angle is calculated using equation 53 for a value of
1 U 3
0.7071 when
-
p 0 ± BW/2,
A - [10.11779 SIN
7.1.2
2
such
that
f(p)
similar to the sin(x)/x antenna.
(BW/2)] 1 / 2
-
The
(61)
Diffraction/Intermediate Region Models Beyond
the
horizon,
electric
field are
ranges,
tropospheric
from
the
chief contributions
diffraction and,
scatter.
The
103
at
to
the
somewhat greater
diffraction
field
can be
I I represented as the
a sum over
solution
to
the
and
determine in
the
only
the
the
describing
mode
is
evaporation ducts especially
the
in
involves
the
region.
logarithm
valid
range
This method of
in
the
the
pattern
optical
is
to
the
a
to
to
the
due to
This
is
the
solutions
minimum
are
range
applicable
given by Reed and Russell
rd - rhor +
where
the
rho r
-
3.572
is
((k
and
which the
(1966)
230.2
horizon range
at
factor first
(k 2 /f)
the
from
on
the
last
in
the
range
diffraction
intermediate
field
region ends
is
3 3
I
I
as
1 / 3
(km)
( 62)
,
I
3
given by
H t ) 1/2 +
I
field
interpolation
diffraction region.
The
3
interpolation"
estimate
linear
I
field
close
slowly.
"bold
used
a
adequately
However,
rather
propagation
region
For
or surface-based ducts
and a method of (1951)
are
field converges
describe
former.
originally described by Kerr this
also
solution converges
region"
the
which
theory.
necessary
A single mode may
series
"intermediate
series
single
field.
presence of
the horizon the
the a
to elevated layers,
of modes
fundamental equation of mode
standard atmosphere, rapidly
the possible number
(k Hr)
I
/2)
(km)
1
(63)
,
I for H t and H r is meters. A minimum effective earth 1.33 is assumed for the calculation of rd.
The determine and
diffraction/intermediate path
heights
interference
loss
below
region
as a function of height the
region.
lower
There
angular
are
104
four
models
radius
are
and range
limit
models
of used
of k
used
-
3
to
3
for ranges
the
optical
to calculate
3
U U I loss
in this
then the
region.
If
the evaporation duct height is zero, standard diffraction loss is calculated by the methods
outlined by Blake (1970). If the evaporation duct height is not zero, then the least loss from standard diffraction or a model derived from the NOSC waveguide program is used. If a surface-based
duct
calculate loss.
is present
an empirical
model
is
At somewhat greater ranges troposcatter
used to loss
is
calculated using a model taken from Yeh (1960) which has been modified by the addition of a "frequency gain" factor from Rice, et
3
The
al.
(1965)
that gives
troposcatter
loss
better values for low-altitude paths. is calculated for all range height
combinations beyond r d and added to the standard diffraction or evaporation duct loss until the troposcatter loss is 18 dB less than the applicable loss. Beyond that point only the troposcatter loss is calculated.
I 7.1.2.1
I
I
Standard Diffraction Model
The total propagation loss due to standard diffraction is given by (from equation 12)
- Lfs fL
in
I
terms
20 LOG 1 0 (F)
-
of previously defined quantities.
The loss term Ld is
determined using
Ld
20
-
LOG 1 0 (f(p))
much energy lowest direct
is
directed
ray angle
(65)
,
where the antenna pattern factor,
I
( 64)
L
f(p),
gives
a measure
of how
toward this region and p represents the in the optical region. Blake's (1980)
1
105
I I I standard diffraction model specifies the one-mode solution for F as
F - V(x)
I U(z ) U(z
-
/3
in kilometers,
H
2129.4 f
-
range, x,
is equal
V(x)
in meters,
to r/R
term
I
receiver/target height, The natural
3
units
and height, H, are given by
s
and f in MHz.
(67)
U
( 68)
i
The natural
U
where r is the actual range, and the
natural height, z1 , is equal The
1
.66)
190 f-i/ 3
2
H
to Ht/H.
is called
the
Similarly, z 2 - Hr/H. factor
attenuation
and is
to
3
! V(x)
- 10.99
The U(z) are the decibels,
U(z)
,
"natural units."
scale factors of range, R,
equal
I
transmiting antenna height and
respectively, expressed in
for R
)
x, z I and z 2 are the receiver/target
for a standard atmosphere. range,
2
+ 10
LOG 1 0 (x)
height-gain
-
17.55
functions
x
(dB).
and
(69)
are calculated,
in
as follows
- 20
z : 0.6
LOG 1 0 (z)
106
,
(70)
i
I I IU(z) IU(z)
-
- 4.3 + 51.04
-
19.85
Strictly
(z 0
"4 7
[LOG o(z/0.6)]
1
.4
0.6 < z < 1.0
_ 0.9)
speaking these
z a: 1.0.
(72)
equations are only valid for horizontal
polarization and a perfectly conducting generally
71)
earth,
but
they
are
applicable to other polarizations at frequencies above
100 MHz.
I 7.1.2.2
I
NOSC
Evaporation Duct Model
The evaporation duct
I I
L
-
51.1
+
r
-
F zt-
loss (in dB)
may be written as
10 LOG 1 0 (p)
Fzr +
+ ap
- Ld
73)
L d is defined by equation 65. r is the excitation factor, Fzt and Fzr the height-gain functions for the EM system transmitter and radar target/receiver, respectively, p the (scaled) range and a the attenuation rate. The specific values of these quantities are obtained as functions of the duct height. The functions which produce
these
values are
the result of curve-fitting the
various quantities to waveguide program solutions. by subsitution of equation 73 into equation 12. I -
The waveguide solutions which were
to develop
the
evaporation duct model were made at a single frequency, 9.6 GHz. The evaporation duct solutions for other frequencies share a family
I
used
F is obtained
resemblance,
the height of
the
duct which produces a
particular propagation characteristic varying inversely with the frequency.
This
fact
allows
the
I i
107
solutions
at
9.6 GHz
to be
I i scaled to other frequencies. multiplied by the
RN
ranges and heights are
scale factors
f
4.705 10
-
All actual
74)
and
f 2 /3 ,
ZN - 2.214 10
respectively, 9.6
GHz
( 75)
to scale the solutions at other frequencies to the The coefficients ensure R - Z N - 1 when the
I I 3
3
values.
frequency is
set
equal
to 9600 MHz.
Using these scale factors,
the actual evaporation duct, receiver, and transmitter heights are scaled to the 9.6 GHz equivalents and the range is similarly changed to conform to the 9.6 GHz requirements. scaled
duct height,
height,
6, times
ZN.
A,
is
equal
to
For example, the
3
the actual evaporation duct
Similarly, if r is
the actual
range and H t
the actual EM system transmitter height then the scaled range, p, is R N times r and the scaled transmitter height, zt, ZN times Ht. t
is
The height-gains expressed as a function of height the duct
are
of
scaled duct
two different forms, depending on whether or not
height
The height
given by
gain
is sufficient function
(in
to
support a well-trapped mode.
dB)
for scaled duct heights less
than 10.25 meters may be written as
F(z)
-
CI z C 2 + C3 zC 4 + C5
108
3
l z
t 1.0
,
(76)
5
I I I 3 3
where or
z
the
duct
is
radar
scaled height
of either
target/receiver.
heights
necessary
3
te
between
to obtain
10.25
the
For
and
- Cl
LOG
F(z)
- C-5
(z/4.72) C6+
[SIN(C2
(z/
4
23.3
. 7 2 )Cj
EM system
meters,
two
either
scaled
the
case,
duct
transmitter
the
height, or
are
+ C4
1.0 : z
C7
Z
(77)
( 78)
z > Z
radar
coefficients z
is
the
Ci
scaled
are
determined
height
target/receiver and Z max
of is
the
from
EM
the
system
calculated using
formula
SZ
= 4 e - ' 31(A
where A duct
*
functions
max
In
3
scaled
in dB
I *
transmitter
well-trapped modes,
height-gains
F(z)
the
is
the
heights
10.0)
-
+ 6
scaled duct height. less
than
10.25
(79)
The
meters
coefficients are
calculated
for
scaled
using
the
following formulas
3
Cl
-
(-2.2
'
244A
I
C2
=
(4.062361
104
e
C3 -
(-33.9
C4 -
(1.43012
e-
+
17).
_ (A
1(82)
104
_ (A
3
(80)
2 1 1 8 6 4 C2
+ 4.4961)2)1/2
). 2
_ 201.0128
( 81)
_ 119.569
( 83)
1 1 8 6 4 C4
+ 5.32545)2)1/2
109
4 1
C5 - 41 e.
A + 61
(84)
The coefficients for scaled duct heights between 10.25 and 23.3 meters, are calculated using the following formulas
C1 -
-. 11896
+ 5.5495
C2 -
(1.3291
SIN(.218(A
C3 -
3/2
C4 - 87
(85)
10)-
7 7
) +
.2171
LOGe (A))
,
(313.29
(A
-
I 1
(86)
(87)
-
I I I I 3
1
(88)
25.3) 2 )1/2
U C5 - (Fmax/((Zmax /4.72)C6
C6
,
89)
- (Z max/ 4 .7 2 )(S/Fmax)
C7 - 49.4e
'
1699(A
-
(90)
10) + 30
,
91)
where
1.5 Cl C2
5 I
II S -
5
(Zmax/4.72) 1 1 2 /TAN(C2
110
(Zmax/4.72)3/2)
,
(92)
I i
I and
F
- Cl LOG (SIN(C2
(Zmax/4.72)3/2))
which are necessary to make slopes continuous about Z . equations height
3
will
for
duct
well-trapped modes have
functions
F(z)
and
Using these coefficients
heights
below
an initial
10.25
increase
their in
the
increase with
meters.
The
with height for
a
thereafter displaying very little variation
The minimum scaled height used is
height-gains
93)
of z near the surface, peak and then decrease with
height to some value, with height.
two
C7
-
produce height-gain curves which
scaled
limited range
the
+ C4
1.0
meter and heights below
for
calculating set
the to
this
are
equal
23.3
meters have more
this value.
I
Scaled than the
3
duct
one mode which multiple
modes
combinations
and
the
region
optical
heights
greater
can propagate is
than
in
the
to add constructively at
destructively at others,
interference.
greater
Examples shown in
and a.
of
figure
23.3 meters
are
height-gain curves
factors
The
excitation factor, which
r
the
-
some
of
range/height similar
to
this variation is not the
scaled duct
23.3
meter ducts.
program,
treated as for
effect
evaporation
ducts
are
25.
Two
strength of
I
the
than
The
a condition
Since
predictable without using a waveguide heights
guide.
from equation
mode,
216.7
in dB may be
+ 1.5526A
73
remain is
to
be
a measure
of
specified, the
relative
obtained using
A :
II 111|
3.8
,
r
(94)
I I I I DUCT HEIGHT (m)
0
10.0
50 23.3
40 I- -
0 -
30
~I
20 -
I
10 -
35
40
50
60
80
70
90
100
110
120
dB Figure 25:
r
Example of 9.6 GHz height-gain curves.
-
222,6
The attenuation rate
a
-
(92.516
-
1.1771(A
A >
3.8)
( 95)
3 8
in dB/km is
- (8608.7593
for values of a _: 0.0009, used. It is convenient equation 73, ap, with fir,
-
(A
which is
-
20.2663)2)1/2)
the
lowest
,
attenuation
( 96)
I 1
I I
rate
to replace the attenuation rate term where r is the actual range and
in
I
112
3
I I -
RN.
97)
I The
attenuation rates
orders
I 3
of
magnitude
height) rate.
7.1.2.3
NOSC
Slayers based may
I
I
is on an
as
where
Fzr
is
C -
is
32.44 this
either.
+ 20
the
and L d
used in
is
for
complex
empirical
L - C -Fzr
by
model
+
as
the
several
diffraction
duct
evaporation
experimental
LOG10
(zero
from
elevated
duct model.
data.
The
loss
It
is
(in dB)
20
LOG
1 0
function
(f).
and no
of
dimensions ducts
The
are
normally
affect
duct
greater
than
1 GHz.
model
terminal
with
height
obtained by
This
choice for
Here
C
scale term
of
this
specified as
on
the
rate
which has
terminal model the
is
radar
subsitution of equation
I I 113
only the
dB)
given is not
are
used
used in equation 98
100
height. of MHz
affects
heights.
As
hundreds and
into
of
below,
of
being
The height-gain
calculated
for
target/receiver height. 98
the
frequencies
disadvantage
always
is
term
factors
order of
receiver/target (in
attenuation
frequencies
evaporation
in EREPS
the
radar target/receiver
the
term used
65.
only height-gain
the
for
range or height
unlike
anisotropic
(98)
defined in equation
gain
these
L
height-gain
model
the height
meters,
I
be
Duct Model
a surface-based
fit of
Similarly the
"guide"
is
standard
may
be written
height
I
than the
Surface-Based
NOSC not
the higher duct heights
smaller
meter duct
The
3
for
equation 12.
the F
The height-gain function for the surface-based duct model is calculated as a function of arbitrary
frequency and duct height
for any
I
radar target/receiver height z:
100 < f
Case 1:
Fzr
-
150
-60(z/D
i
-
.5)2
1.14(z/D) - 6.26
Fzr-
-10
z/D <
.8
z/D
.8
( 99)
,
(100)
150 < f 5 350
Case 2:
zr
F
-
10
-
Fzr - 7.5(z/D) 13.3
.5)4
z/D <
1.0
(101)
,
z/D ? 1.0
_ 10
(102)
F zr
-
10
F
-
12.5(z/D) 8
200(z/D
-
.5)4
z/D
15
< 1.0
,
z/D a 1.0
(103)
Is
produced by the
1
(104)
I
zr
Here D
1 3
f > 350
Case 3:
3 3
U
200(z/D
-
3 I I 3
the
duct
these
height-gain
height.
formulas curves
as should be expected
Examples
are
are
given
of the height-gain
in figure
characteristic
26.
The
curves
shapes
of
3
of well-trapped modes
from a surface-based duct.
114
3
32 150 >f(MHz)> 100: A 350 >f(MHz) 150: B
C
f(MHz) > 350: C
I I I U 3
-20
0
-10
10
dB Figure
26:
Height-gain
curve
for
surface-based
duct
of
arbitary
height
I The
3
the
M-versus-height
10%
of
10
to
/ae) .
height
duct
are
Below the If
is
a
trapping
below
of
the
the
the
assumes
top
layer
and of
the
effective
transmitter
trapping
a
laycr
and a
that
the
certain
is
assumption
layer
the
trapping
inverse
model
The
between
the
both
duct
profile.
refractivity
zero.
equal
I
the
modified is
3
surface-based
that
the
duct
the
the
and
the
radar
"skip-zone"
in
surface
gradient
radius
to
upper
difference
refractivity earth
shape
(dM/dh
is -
target/reciever is
modeled.
A
minimum ray path between
the
two terminal heights is calculated
and
set
as
the
resulting
trapping
range
by the duct
is
exists
(i.e,
115
the
minimum
range
at
which
full
the far end of the skip zone).
I I At
lesser
ranges,
frequencies, model
is
7.1.3
an
increase
based
on
Troposcatter
ranges
electric field.
in decibels
I dB/km
Yeh
in
the
(1960)
than
all the
the
troposphere gives
the
-
-
0.2
rang(-, rho r is value, and H
rhor)/k
+ 20 LOG 1 0 (r)
Ns
+ H
Ld
horizon begins
to
troposcatter
3
(105)
.
the horizon range, N is the surface is -he frequency-gain function from
al.
(1965). L d is defined in equation 65. F is obtained subsitution of equation 105 into equation 12. The
troposcatter model
can be effectively
suppressed by
if comparisons
desired with other
models which
for
for
ranges,
as
30 LOG 1 0 (f)
Here r is the refractivity
greater
irregularities
114.9 + 0.08984(r
+
by
as
greater
I
sufficiently
dominate the
et
set At
Region Model
from
Rice
is
measured data.
scattering
L -
loss
given by equation 98.
At
loss
of
are
setting N - 0 do not
account
troposcatter.
The importance frequency
for
low
is very
calculation
equal
frequency
gain
antenna
low.
of
the
(s
r 8)/(I
The
function,
heights, procedure
effective
H
,
i.
especially
- imarily if
the
for obtaining H 0
scattering
height,
ho,
of
system
requires which
a is
toI
ho -
+ s)
(km)
116
(106)
3 5
5
I I I where
3
figure
r
is
27,
1
s
I
ground range, e
the and
s is
/
"
the
scattering angle,
as
shown in
defined by
(107)
10.0 2: s 2- 0.10.
x
SCATTER VOLUME
I\
~ho
HI
H
*
e2
I
Figure
i
The
27 :
angles
1
Geometry
from
for
troposcatter loss
these equations
are
117
calculations.
given by
I I 0
-
r/a
1
-
r 1 /ae'
82
-
r 2 /a
(110)
(111)
,
8/2 + 81 + (H t - H r)/r
-
X
(109)
,
=
8/2
+ 82
in terms
of
the
effective
ranges
I
r
and
r
+
(H r
-
Ht)/r
earth
terminal
(112)
,
(113)
,
radius,
ae
the
heights H t and Hr,
range, r, as shown in figure 27.
tangent and
The tangent ranges,
the
1
3 I I
ray
total
r I and
r2 ,
are equal to
The
r I f (.002
ae H t)1/2
r 2 - (.002
a e H r ) /2
tI
(km)
(114)
,
(km).
(115)
I I
frequency gain function is then defined as
H
1
+ AH
-
HI
-
(Ho(R
I
) + Ho(R
2
)1/2
+
AH
118
H0
0.0
(dB).
(116)
I
IIf
AH0is
H1
h
greater than H 1 then H 0is equal to twice the value of
function
3H(R
1)
1 is calculated using
c1
(R1 + c 2 ) 43,(117)
CR ) o( 2
3
where
c1I (R2 + c2 )-
R Iand R 2are
system frequency,
functions
1
c2
-
the
terminal
heights'
and EM
(119)
f Hr
+
(120)
,
c1I and c2 are
16.3
of
f H tE)
R2-00419
3c 3 I
18
f in MHz,
RI-00419
and the terms
4/3,(18
-
defined as
13.3 q~
- 0.40 + 0.16 q7
(121)
,
(122)
.
The factor q7 must be calculated as a function of h
?is
(0.5696 h0 )[1
+
(0.031
-
EXP(-3.8 h 06 10- 6
0.00232 N s+
5.0 ;t n
119
5.67N s210- 6
0.01.
(123)
U I I The
remaining term, AH1
AH
- 6[0.60
where
q is
7.1.4
all
model
0
(q)
(dB),
(124)
R1 )
10.0
q
! 0.10
(125)
U
term AH
is
zero
of
3.6 dB
for
Y.
for
4.0,
s
highly
- 1.0,
or q - 1.0
asymmetrical
paths
i i
Water Vapor Absorption Model
loss
attributable
other losses is
taken
dependent
on
temperature is
LOG 1
1.0.
The to
(s)
i
and has a maximum value -
10
given by
The correction
9,
calculated using
LOG 1 0 (0s)]LOG
-
q - R 2 /(s
when
is
equal
of
computed by
directly
the 15
C is
the
models
of
section
from CCIR Recommendations
absolute °
to water vapor absorption
humidity
assumed.
in
7.1.
(1986)
grams/cubic
The water vapor
is added The
and
is
meter.
A
absorption loss
to
L
where a wv
I =
is
attenuation
r a
,
(126)
the
water vapor
rate
in dB/km
awv - (0.067 + awvl
attenuation
rate.
The
water
vapor
3
is
+ a wv2 + a wv3)f
H a 100.0
,
(127)
I 120i
I I I temperature
3
is
equal
of
150
i
The water vapor absorption loss
to
wV
U
C is assumed.
where a WV
wvra
is
attenuation
-he water vapor attenuation rate
a
(]26)
-
in
dB/km
rate
The
water vapor
is
(0.067 + a 1
+ awv 2
+ awv3)f2
H
100.0
,
(127)
I where H is
the absolute humidity,
f is
the EM system frequency in
MHz and
I
aa
= 3 /
Swv2
= 9 / ((0.001
if wv3 -4.3
For
frequencies
((0.001 f
f
/ ((0.001
below
-
22.3)2 + 7.3)
-
183.3)2 + 6)
f
323.8)
about
10
(128)
,
(129)
+ 10).
(130)
GHz, this attenuation is but at the highest frequencies used in EREPS, 20 Ghz, the contribution can be quite noticeable, in particular at long ranges. No model is included for oxygen absorption, since the
negligible,
attenuation is negligible below 20 GHz.
I I !
121
I U U an
M-unit
array
with
like-numbered array. two
arrays
the
corresponding
A third array can be
which contains
the
gradient
M-unit
value
in
a
constructed from these
between
adjacent
I
layers.
The general definition for this array is
dMdh
where
elements,
trapping
layers.
element,
the H-unit
A
for
the
is
dMdh3
element
in
the
is
RAYS pressure,
also
relate
these
Dutton
(1968).
M(z)
where z is section
terms H
maximum
is
equal
the height
of
(4/3 earth) highest
the
j
is
values
not allowing
height
dMdh
gradient
is
array
index of
zero
I
are
i
height
the of
the
the
are
not
the M-unit values
of
equal.
to
input
relative
to M are
H.3 denote
values
the
dMdh
to
you
and
- N + 0.0157
the
M-profile
humidity.
taken from Berry
The
(1945),
in
terms
models
of
that
and Bean
and
to
z
where
(132)
,
N
is
determined
from
equation
2
I I
of
2.2.2.
A critical heights
allows
temperature
above
array.
to be
(131)
the
atmosphere
.000118, where
equivalent
adjacent height values
H)
Negative
gradient =
H
-
1
array and
standard
that
allowed, which
M i)/(Hi+
respectively.
usually defined
last
(M i+-
M.J denote
the
array
3
10
-
within
launch
ducts.
angle This
(positive or negative)
positive critical
angle
can be
determined
critical angle
for
transmitter
angle
is
defined
trapped
in
the
as
duct.
the The
is given by
1 122I
U a
I 3
the
while Ht
1
-
[2
maximum negative critical angle is equal to
the M-unit value
is
(133)
Mn)]I
(MHt
transmitter
the
at
-a
and Mmin
Here
.
is
the
mimimum M-unit value at some height greater than H t . H t must be in the duct for equation 133 to be valid, though if H t is above the duct, -a c would define the launch angle for a ray tangent to Rays launched with angles ac the duct at some range. -ac will be trapped within the duct.
the top of
S>
a <
The general raytrace equations using the H, M and dMdh arrays can be divided into three categories, rays with the terminal range known, rays with the terminal height known, and Figure 28 rays with the terminal elevation angle known. a ray with a positive launch angle, but the equations apply to negative launch angles also when proper care is taken with respect to the layer indices and sign of the launch angle. illustrates
equations given apply only to range and height values within All heights are in meters and ranges in individual layers.
The
kilometers. Case
a'
-
I
2:
0.002 dMdh i (h'
(a
r' - r +
Case
0.
1: h' known, a
(a'
r' known, a
a'
-
-
#
a + dMdh.
(134)
(135)
a)/dMdh
0.
(r'
-
r)
,
I I
- h))
123
(136)
H14
28Iata Fiur aibe
figr te 28:
e
haeirac
Varible
th
124
a
a
ecedamxmm(r
I I U 5
I
in the than
case of
h'
In
.
this
(minimum) are
r'
-
a downgoing case
ray, a minimum) height
the
a'
r
- a/dMdh.
covered by
the
this
if
dMdh
case
at
141
this
above i
ray
will
can
of
altitude error. of
the
the
ray maximum
(140)
dMdhi)
range
0
the
(141)
,
and height. is
ray
become
the
will
a
One
special become
downgoing
iteratively
used
to
an
unique
case
case
-
a
not
0.
In
upgoing ray,
ray.
Equations
trace ray paths
if 134
through
stratified atmosphere.
the user-selected options Altitude error is
in RAYS
is a display of
computed as the absolute value
difference between a ray's height and the height at which
a ray with the under
>
be
the user-specified
One
of
,
equations
dMdh
< 0 the
i
through *
0
-
and height
(greater)
given by
h' - h - a 2/(0.002
while
range
less
standard
Superrefractive errors
such
same
elevation
conditions and
that
angle
(i.e.,
a
would single
be
at
altitude
is
same
gradient of
trapping gradients usually
apparent
the
118 M/km).
produce
greater
range
altitude
than the
actual
altitude.
*
7.3
Sea
Clutter Models
Sea-surface PROPR
3
radar
or
PROPH
clutter
graphics
signal-to-noise
or height.
The
plot of
ratio of
clutter
the
power
sea
or
is
displayed
option 4.
level
clutter
in decibels level
is
clutter-to-noise
the
In
average
EREPS
this graphics is
plotted
displayed by power.
clutter
125
in
when
using
option,
versus
the
range
superimposing
Either
power ± 5 dB,
the the
a
average clutter
I I U power bounds, can be displayed. The clutter-to-noise ratio in decibels is equivalent to Pc - P , where P is the clutter powerI in dB and P is the noise power in dB. The average clutter power in decibels
where
r the
and
c
range is
antenna
gain
associated surface.
in km,
the
Pn
in
and
the
ray
10
the
LOG 1
0
width
in microseconds. of
range
NuSC-modified
angle
model for
but
is
thought
the
clutter
under
to
in
of
the
1978).
this it
in
dB
and
is
the
factor the
included
Georgia
models
The
GIT
pulse
ratio
is
a
of
model The
the
Technology
The
grazing
GIT
model allow
normal horizon
NOSC model for
provides
low
grazing
sometimes
dramatic
clutter power
I
using a
NOSC modifications
The
ducting conditions. the
the
differ below 1
beyond
conditions.
on
is
in EREPS
Institute
extended
the
sea
a constant.
are
± 5 dB.
r
clutter-to-noise
to
surface-based ducts
is
G
(143)
valid
than
dB,
I
be
ducting
in
+ Nf
These
to be
dB.
intercepts
and ducting conditions.
calculations
wavelength in
pattern
states
reflectivity
effects of
PROPH
that
(142)1
,
losses
in
sea
angle/evaporation
modeled
for
system
a
is
figure
In PROPR
version
evaporation
greater
10 15))
+
the
is
antenna
launch angle, a, in decibels
A
L
-
section
the
clutter effects
(Horst,
low
in kW,
cross is
receiver noise
Sea-surface
(GIT)
f(a)
(4/(r
Nf
+ 2 Gt
miscellaneous
clutter
dB
where
function
is
noise power
-
is
Ls
average
with
The
f(a) 4)
transmitted power
the
is
Pt
given by
+ 10 LOG 1 0 (P t A 2 r
-123.0
Pc-
m,
is
level
are
not
3
EREPS.
I 126
I I i The
3
GIT
model
decibels relative
where
is
of
the
dependent
clutter cross radar
in
cross-section,
as
(144)
,
section per unit cell
resolution
area a*
(dB).
(dB) is
a
for a horizontally polarized rpolarization variable,
radar
-
and
10
LOG 1(.0000039
A
00.4 Ai
(dB)
Au A W)
(145)
for a vertically polarized radar
I
- a H °H - 10LOe 1.05 LOG
a
3 *
(dBsm)
average
area
H
i
clutter
to one-square meter,
the
the
A cis
Iand
I
a*
the
+ Ac
- a*
a
gives
+
1.27
avg + 0.02) (havg
4
) + 9.70
(havg
+ 0.02)
LOGe (0 + 10-
+
1.09
f ?
LOG e (A)
3000
(146)
,
or
I a
0H
-
U
+
-
2.46
1.73
LOG
LOGe (0 +
10
4
) +
+
22.2
3.76
LOG
f < 3000
(A)
(147)
,
I
where
0
the
is
average wave circularly
grazing
height
angle,
in meters
polarized system
by Nathanson
is
(see
and A is
figure
24) ,
havg
the wavelength.
calculated following
a
a°
is C
the for
a
suggestion
(1969)
127
I
I
I I aoC -
where
a*ma x
is
the
Aw
is
max-
a
is
the
wind
grazing angles
The
speed
between 0.10
"fully
is
sea).
a*
to
142
is
A.
factor
and
applicable
for
10.I
on
be
calculated above.
upwind/downwind
sea
state
than wave height.
assumed
arisen"
the
Equation
and
of
or a V as is
factor.
dependence
height
of a
factor, A u
function of wind speed wave
(148)
,
larger
interference the
6
only
a
is
more
However
function
The average wave height
in
of is
strongly EREPS,
wind
speed
a
the (a
given by
I
25 h avg-
where is
is
the
(149)
,
wind speed
in m/sec.
The wind speed
factor,
I
AW,
determined using
Aw
The
W
(W s/8.67)
-
[(1.9425
interference
W s)/(l
+ W s/
term, A i ,
4
Ai
where
a
-
is a
-
a
4
15
) ] 1.1(A
+
is
defined as
)
,
0.02)
0.4
(150)
I I
4
/(l.0
+ a
4
(151)
roughness parameter
(14.4
given by
A + 5.5)(0 havg )/A.
(152)
I 128I
I I I
The upwind/downwind factor, Au,
is
determined using
-0.4 A
COS(O)
EXP[0.2
-
(1
-
2.8 0)(A
0.02)
+
]
(153)
,
where 0 is the angle between the radar antenna boresight and the upwind direction (0* to 180). The area of the radar clutter cell,
resolution
A c - 10 LOG A
I
the
range
e H c r ce)/(4 LOG (2))]
(154)
c
the speed
r
radar
system compressed pulse
antenna horizontal
beamwidth
for
of
light
sec,
and
in m/sec,
eH
is
the
radar
the
in radians.
angles
grazing where
width in
below 2 GHz
frequencies
range
maximum
in km,
r
r is
alteration
in 144
equation
the GIT the is
model
range
used without
is
to
0.10
applicable
is
10
°
.
The
determined
using
R.5(-2
uRi
I where angle
grazing
the for
a ae
052
any
-
I I U
10 [(1000
where
For
*
calculated using
is
Ac,
range
+ ((2
k
angle
e
)2 +
-
.008 H t
t
.001745 radians
than R lim
less
H t/(1000 r)
-
a
r/(2
a e)
129
a )1/2) e
(0.1°).
(155)
The grazing
is determined by
(radians)
,
(156)
for all
0 s l0.
these values
The
launch
angle a associated with
each of
of 0 is given by equation 23 with the H r term equal
to zero. At radar range analogous
frequencies
to equation
of
2 GHz and greater, the maximum
155
is determined using a raytrace for the evaporation duct profile. The limiting ray for this case is the ray launched at the transmitter height that intersects the surface at
the
angle equal
to
a - 10 3(
a
-
2
(MHt
farthest
-
-103 ( 2 (MHt
Mm n))1
-
possible
/ 2
6
-
Mmin)) 1/2
range.
This
t < 6
i06
Ht
6
ray has
.
launch
(radians),
(157)
(radians),
(158)
where MHt is the M-unit value at H t and Mmi n is the minimum value on the evaporation duct height profile height,
6).
The M-value
(which occurs
at
the duct
at any height z for an evaportion duct
is calculated using
M(z)
- M
+ (z/8)
where M s is equal to
-
(6/8)
LOGe ((z
+
.00015)/.00015),
(159)
the M-unit value at the surface and S is the
evaporation duct height. Thus Mmi n is determined using equation 159 with z - 6. The evaporation duct profile used in the raytrace
is
determined using equation
0.368, 1.0, 2.7,
7.4,
159
for heights z
-
0.135,
- U1t for H t < 54.6.
20.1 and 54.6 meters as well as z - 6 and z If 11t > 54.6 a standard atmospheric gradient
of 118 M/km is added
to the M-unit
value at
54.6 meters.
This
piecewise-continuous profile of M versus height is used to trace
130
I rays
I 100.
The grazing angle associated with a is determined using
0 - (a2
1
such that
to determine range for all ranges less than R
_ 2(MH
(160)
M s)10 6 )1/2
t
for all ranges less than Rlim*
for
The clutter level using
the
clutter
average
is determined
ranges beyond R lim cross
section,
at Rlim
a*,
The
.
reflectivity at this limiting grazing angle is modified using the That is evaporation duct attenuation rate from equation 97.
I $
a° -
where
a*li m
m
r > rli
2 0 r
-Oli
the
denotes
angle associated with Rli
m
value of a*
at
the
m
(161)
,
limiting
grazing
determined from equation 156 or 160.
Radar Models
7.4
I
PROPR, PROPH and COVER all contain the ability to convert radar system parameters such as frequency, pulse length, etc., to The models free-space range for further use within the program. to
do
this conversion are
of radar
calculations
"integration",
5
and
taken from Blake
are allowed
"visibility
calculation is normally used for uses
noncoherent pulse
The signal-to-noise
a
by
the
factor."
(1980). program A
Three types "simple",
"simple"
rotating, pulsed
radar
type that
integration to increase its sensitivity.
ratio
required for
a given probability
of
detection and false alarm rate is known as either the visibility factor or the detectability factor, D , For a simple radar with a uniform-weight integrator and a square-law detector D
I
131
is
I I U Do
[X0/(4 N p )](I
-
+
(I +
(16
Np/X 0 ) 1/2Lf
(162)
,
where
(gfa + gd)22
2
gfa -
gd
t
Here N per
3 6
1.23
0.9(2
-
is
the
scan),
Lf
t(l
-
2 I1/2 ) /2
(166)
of pulses
the is
where
the
loss,
probability of
Pd
the detector
is
false
the
(8 H fp)/(6
0h )
Np
in Hz,
fluctuation
fluctuating
of the
(167)
I
target.
If
loss, a
and Oh Lf,
[-LOG e(Pd)
is
is
1,
132
)
]1
is
the
pulse
rate
a Swerling Case 0,
target
kF - 1,
(1 + gd/gfa
fp
the horizontal scan
1 for
fluctuating
calculated for a Swerling Case
Lf -
For
1.0
eH is the horizontal beam width in degrees,
The
(hits
probability
alarms.
I I 3
faa
repetition frequency rpm.
integrated by
fluctuation
simple radarI
Np
(165)
1)
Pd
detection, and Pfa
t
3
(164)
'
[LOG10(Pfa)]
number is
(163)
is
selected
chi-square
in
nonLf
is
target
(168)
I I I While
between
i
is
type radar
where
coherent
[X /(4N p)
-
]
the
[1 +
for the
D
)]
(16/X
type
must supply
dealing
"visibility
option
This
complicated signal processing
of equation 1.34
arbitrarily set
set
to
2900
factor",
then the user
most
K.
of
in place
useful
systems
to
users
that
With
to
the
to calculate
The bandwidth correction
range.
temperature
If
radar
is used
free-space detection was
the
the
radar
defined.
use
schemes.
1.34
equation
(1980)
Blake's
be
may
(169)
to be used
factor
sophisticated
modern
with
to
value of visibility
the
162.
equation
set
is
"integration"
Lf
/2)
quantities have been previously
where all
linear
is used
integration
(1 +
difference
the
commonly used
more
than 1 dB.
generally less
detectors
calculation i
and
square-law detectors
D0
i
assumed a square-law detector,
equation 162
1,
some
and
the
algebra
radar
factor,
system this
Cb,
noise
equation
becomes
I
-
R
where
Pt
section
is
58.0
the
frequency Z is
parameters.
1
Z
|
transmitter power
in square meters,
system's
I I
[(Pt a T Z)/f2]
-
[2G
r is the
in MHz,
I/ 4
(km)
in kW,
a
is
the
(170)
,
target
pulse width in ps,
and Z is
f is
a function of several
crossthe
EM
radar
given by
- Nf
-
D
-
s]/10
10
,1
133
(171)
I I I where
G
figure
is in
the dB,
miscellaneous
antenna gain in D
is
dB,
previously
Nf is
the
defined,
system losses in dB.
receiver and
L
noise
is
s
All losses not specifically
mentioned above must be accounted for in the system losses, as
transmission
processing
loss,
threshold range
for
line
beam-shape
PROPH
or
from equation 170
The target
radar
signal
S/N
where
Pr
noise
is
the
width
and
in
the
mismatch
etc.
into equation
ratio
is
The
12
of
to
the
power, which
signal range
subsituting
ratio
is
derived
from
equation 1.18.
The
target
in dB
power
is
I (172)
received dBW,
target power
The
noise
receiver noise
received target power
in dBW
in dBW and Pn
power
figure
is
given
is
the
system
a function of the by
equation
pulse
143.
The
is
I
424 Pr
where and of
7.5
r
is
the
all other F is
LOG10[(P
range
a F )/(f
t
in km,
terms are
discussed
as
F is
r
the
Lf)]
+ 20
Ls ,
(173)
pattern propagation factor,
previously defined.
in section
-
The
calculation
7.1.
I 3
I
ESM Models
The as
+ 10
-73.4
I
received
Pn
-
the
section 7.1.
from Blake's
equal
loss,
such
free-space
obtained by
signal-to-noise
sytem noise
Pr
-
power
loss,
power calculated
the
filter
PROPR can be
target
signal-to-noise divided by
loss,
the
the
propagation
decibel
difference
threshold
for
between
134
the
ESM systems effective
is calculated
radiated
power
I
I I I and the
ESM receiver
system losses. G in
dBi,
sensitivity,
as
adjusted by
For peak power P in kW,
appropriate
transmitter antenna
gain
ESM
system sensitivity S in dBm, and system losses L in dB, the propagation threshold T in dB, is calculated as
T -
I
10LOG 1 0 (P)
-
5 dB,
then
T
+ G
-
S
if P = 100 kW,
For example, L
+ 60
185
-
dB.
- L s.
G -
(174)
S -
30 dBi,
Normally,
includes receiving antenna gain and line
ESM
-80
dBm,
and
system sensitivity
losses.
Thus
L
would
be used to account for the emitter's transmission line losses and other losses associated with the transmitter. Under PROPR display option 2, the threshold loss propagation-loss display as a dashed line. less
to
T
is plotted on the Propagation losses
than the threshold correspond to intercept capability.
The same display option and system parameters may be used assess communications systems. The only difference is that
system sensitivity should be adjusted to account for to-noise
I
margin
Implementations
7.6.1
with
a
given
level
of
of the Models
PROPR The
purpose
of
other quantities sufficient program
and
begins
PROPR
already
detail
region lobes *
associated
communications quality.
7.6
I
ratio
the signal-
to
present propagation loss (or described) versus range, showing
clearly
other by
is
to
define
relevant
determining
are
valid.
of
optical The
the
the
maximum such
Computations
135
structure
propagation mechanisms.
transmitter to the reflection point rl calculations
the
range
from
that optical for
each lobe
region in
the
I I I optical
region
corresponding
are
performed
next
null
propagation plotted. been
is
found
to give
computations
For
sufficient excess
are
and/or
and
troposcatter limit,
heights
greater
from
vapor Of
than
the other
variable
in the
of
range limit,
range
used.
7.6.2
smaller
is
between
a range
in
used.
is
other
the the
computed
and
optical
range
point
within
added to of
is
rl
regions. of
the
in
the
PROPR,
the
At
losses.
independent
ranges
1/100th
the
duct
water-
the other
as
the
I 3
than the
already described, and
increment
of
(for
less
I
for
diffraction region.
computed
I
region
diffraction, ducting,
is
ranges
use
region
optical
last
have
For all ranges beyond
loss
computed and the
the
used when it
all
the
interpolation
applicable
region, as
all
to
which
range points
After the
rI and
at
are
loss and
Linear
duct
At
in PROPR is
for
range
The
I
point
minimum valid
point
the
starting
r
the
use
beyond
the
3
total plotted
I
PROPH
fixed the
range. optical
Computations determine using
The
for
a plot of
first
limit,
step
each
a Newton-method
computed
loss is
lobe
in
versus
receiver
to determine
in a similar
the next higher
successive nulls is
first
models.
PROPH generates
at
used
zero) and
optical r
optical
the
surface-based
particular note
is
next
8 points
resolution
models are
attenuation loss
total
is
the
into
total
found.
at and beyond rd,
optical
loss
the
the
computation.
r d is in dB
or
these
completed,
factor
region
ranges
linearly
connecting
diffraction models
optical
last null
loss and corresponding
requiring
propagation
the
divided
The vectors
without
find
to a null using a Newton-method iteration.
interval between either the
to
manner
the
height
region
are
receiver height corresponding
iteration.
The
is split into multiple
and plotted.
For each
limit, a check is made to determine
136
if
height
made
to
to a null
for which
fixed
loss
the
optical
range
exceeds
height below
3
PROPR.
interval between
segments the
a
the receiver height
as described for
optical
at
3 3 3
I
I the
minimum
valid
range
for diffraction. If it is, the appropriate diffraction, ducting, and/or troposcatter model is used. Otherwise, linear interpolation is used on the propagation factor in dB between the optical-limit maximum range and the diffraction-region minimum range at the current receiver height.
3
As with PROPR, loss
from
heights)
the
and
water-vapor the
3
surface-based
the
attenuation is
the
increment
height in optical
the
and
2 meters
to
At
of
in the
1/300th
of
that
for all
the
lesser
heights,
Note
of
the
non-zero duct
all
loss.
1/300th
1/10th
limits
or
(for
receiver height
region,
diffraction
greater of
added to the
is
limit,
model
is used.
being set
optical
optical
duct
other models
independent variable
with
the
at heights below the
the
in PROPH
calculations,
the maximum plotted height
between
the
interpolation region, and
the
maximum plotted height
otherwise.
I 7.6.3
I
COVER
The purpose contour
that
always be
has
been
transmitter
and
receiver
long
Sand
point
ranges,
low
made
to the but
receiver
propagation
to generate an altitude-versus-range
than a specified value.
assumption
at
that
is
can
be
being
the
ray to
This
a constant
for
any
in turn permits
fast
range
at
When applying COVER to
that
angle.
receiver heights, PROPR.
If
model
there
it is
is
a
and
easy
good
idea
a substantial
to use.
137
ray
is
short
check
difference
in
quite short
the
the
good
ranges in
elevation of
the
from the
results
computation
to
path
error at it
will
between
assumption
However,
loss
optical region, an
path
the
in substantial
altitudes.
factor
In the
parallel
receiver.
propagation
which
the
I I I
is
defines an area within which
less
reflection
3
of COVER
the
angle, maximum
ranges and results
results,
low
with
PROPR is
I I I The angle
at
method
COVER the
optical
limit.
iteration is
corresponding and
algorithm begins
to give
good definition
required
lobes have
ranges at
the
angle
selected.
a
that
sufficiently
height
to
small the
contours
height
1/20th
created by each region
Water-vapor
absorption
region
through
COVER, since not
affect
the
shape an
below
the
included
the
the
almost
coverage
Newton-
the
a
I
direct
are used per
lobes.
lobes
is
After of
drawn
used
limit,
to
factors.
up
the
effects
is
are
at
the
and
a
All
through
beyond-horizon
to the not
I
i
over-
color.
region
in the
good
used.
and
shade
optical
absorption loss
give
Otherwise
region,
single
U
and beamwidth
optical
is
in the
always be
the
For ducting conditions,
range, and
Troposcatter
a
"envelope" contour
envelope
filled with is
of
total plot height
of maximum
they will
the
angles
height-gain
of
addition of
or ducting losses.
phase
increment
lobe,
are
iterative solution
between
receiver height.
the-horizon
an
angle
antenna pattern
ranges
vertical
increment of
the
elevation
region,
all higher-angle
on
and
is
the
the
next higher elevation angle
been completed,
depends
variable
definition
optical
such
to
maximum of
For heights
independent
the
find the
Fourteen
the
an
determining
to a predetermined phase
the
to
In
used to
reflected paths.
lobe
by
diffraction
considered
such high values
as
I 3
in to
diagram.
I 7.6.4
RAYS
The
purpose
of
RAYS
ray-path trajectories specifies the is
traced based each
give
ray.
At
and
range
calculate
limits,
on a series
best
variable
each step,
and of
are
compromise in the this
and
a height-versus-range profile,
found within
layer
of
the
is
138
series The
desired.
that
and
are
of
user
height, Each
performed
in the
profile.
resolution,
layer.
and
a
If the
new ray
I 3
ray
the
elevation angle along the
incremented
current
a
display.
specified
speed is
plot
transmitter
rays
calculations
raytrace
angle
the
number of
linear-refracLivity
the
independent
to
refractive-index
elevation angle
within To
the
on
is
height leaves
I 3 3 5
U 3
a the
current
layer,
boundary, and above
then
the
range
is
calculated at
the elevation angle
is
incremented in the layer
or below.
As
the layer
each
layer is entered, the refractivity gradient must be examined to determine if the elevation angle in that layer will be increasing or decreasing. Tests must be included to determine where rays will reach a maximum or minimum height, to ensure is considered.
that the corresponding elevation angle
For the
last step only, a height
the maximum range within For
3 s 3
the
is calculated at
the current layer.
altitude-error
option,
a
second
raytrace
for
a
standard atmosphere is computed at each point along the ray, such that the altitude difference between the actual and standard ray paths can be determined.
The color of each
determined based on
height difference
the
ray
segment
is then
and a user-defined
scale.
7.6.5
FFACTR The purpose
3
of zero
propagation geometry, calculate less
of FFACTR is
factor in dB and environmental the
optical
return
for a series parameters.
limit
than the optical limit,
to
range.
If
a single
value of
of specified The first the
a solution to the
the
system, step is to
specified range is cubic
equation to
determine the reflection point in the optical region is performed along with all other optical region calculations propagation factor. If the specified range is optical
limit,
calculations
is
these two limits,
the
minimum
determined.
to determine the greater than the
range
for
If
specified range
the
valid
diffraction is between
linear interpolation of the propagation
factor
in dB versus range is performed to compute the desired result. For ranges beyond the minimum diffraction range, the appropriate
3
diffraction, ducting, and/or troposcatter model is used. For all ranges heyond the optical limit, the lesser loss of the surfacebased duct model (for non-zero duct heights) and the other
139
applicable
models
vapor absorption
is
used.
At
all
is added.
140
ranges,
the
loss
from
water
I I I I I I I I I I I I I I I I I I 5
II I
a 8.0
Application Example
£
This PROPR
and
application example
SDS
3
in
Mykonos
m
was
on by
band)
were
above for
and
msl. each
Richter
4.8
km,
35.2
periods
frequency, at
m
above
Naxos
Hitney
mean
m above
were for
msl
and
level
sea
located at
positioned at L,
The range
somewhat
(1988).
(S band),
(Ku band) was
antennas
and
S,
and
X
separation
over-the-horizon
Horizontal polarization was used at all four
Propagation loss was measured measured
24 hours per
is
first
for
four three-week
by
August
and
a 5 minute period and
in
using
29.
to
EREPS
the climatology
figure
distribution shown
during
November.
All
recorded every
15
day.
step
to obtain
illustrated
only
over
averaged
The effects
and
3.0 GHz
for Ku band.
a
of
in February, April, August, and November, except for Ku
were
3
19.2
to
corresponding
band which was
minutes,
receiving
17.8 m above msl
at
frequencies.
data
located at
statistical
Islands
(L band),
1.0 GHz
Three
propagation path.
3
reported
assess
based on a propagation
is
Greek
Also a transmitter at 18.0 CHz
Mykonos bands
1972
(X
GHz
(msl). 4.5
the
and
to
The example
performed between
co illustrate how
included
together
used
transmitters at
On Naxos, 9.6
be
performance.
propagation experiment
may
is
for
The
assess
the
propagation
Greek Islands
evaporation
duct
area, height
that evaporation ducting effects
indicates
are
quite strong. The
3
I I I
step
next
investigate
the
parameters.
At
propagation
loss
in
this
of propagation
sensitivity X
band of
for
173
example
dB
example, for
Islands experiment under standard
141
the
is
to
loss
figure
use
to
to environmental 30
geometries
atmospheric
PROPR
indicates of
the
conditions.
a
Greek
I I I I EVD HT
x OCCUR
8 TO 2 n 2 TO 4 n 4TO 6m 6 TO 8 n 8 TO 18 m 18 TO 12 m 12 TO 14 n 14 TO 16 m 16 TO 18 m 18 TO 28 m 28 TO 22 n 22 TO 24 m 24 TO 26 m 26 TO 28 n 28 TO 38 m 38 TO 32 32 TO 34 m 34 TO 36 n 36 TO 38 m 38 TO 48
Figure
29:
the
18
15
28
ANNUAL SURFACE DUCT SUMMARY SURFACE OBS: MS 142
9.5 A 11.8 13.4 12.9 11.2 8.? 6.? 4.6 3.2 2.1 1.4 8.9 8 .5 8.4 8.2 8.1
25 ____
:
LATITUDE:
P 0 R A T 1 0 N
30 TO 48 N
UPPER AIR OBS: AUG
I
6 STATIONS AVERAGED
D U
C T H
SBD OCCURRENCE: AVG SBD HT: AUG NSUBS:
T
AUG X:
11.8 x 117m 334 1.49
8.2
that while
propagation
read values
I
LONGITUDE: 28 TO 38 E AVG EUD HT: 13.1 m AVG UIND SP: 12.3 XTS SAMPLE SIZE: 187842 OBS
SDS summary for Marsden square
Note read
5
2.0 3.4 E 6.7 V
8.1
>48 m
8
that
are
the
XHAIR
loss values
mode from
may be the
slightly different
3
142.
readily
used
to
display, one user may than
another
due
to
display resolution. In any case, readings should be accurate to about 0.5 dB, which is better than the probable overall accuracy of
the
models.
parameter
at
By
using other
EREPS
a time and using the
programs
overlay
can easily simulate various conditions
feature
or by varying one of
PROPR,
I
5
you
and see the effects on
1 142
5
U U I I S18p R 0 P 120A G
Free-space propagation loss at a range of 3G.2 km 143 dB rag
A T 148I 0
N
FREQ MHz 9688 POLARIZATION HOE TRAMHT m 4.8 REC HT n 19.2 ANT TYPE OMNI B deg N/A ELEV ANG deg N/A EVD HT X
NSUBS
160-
8
1.49
334
ABS HUM
L 0 S S 188-
8
m
m
.SBDHT
9/m3 ?.5
SP kts 12.3 1NZ FREE-SPACE RANGE or dB THRESHOLDS Diffraction region propagation loss at arange of 35.2kn= 173 dB
d 288-
I
6
18
28 RANE
Figure
30:
PROPR display
I
I
38
48
58 FREE SPACE
km
for X band frequency
and geometries
in
the Greek Island experiment within a non-ducting environment.
propagation
3
shows
loss
a RAYS
product
the
given
for a 117
path.
Therefore, likely
to
such ducts the
one
the
Greek
evaporation
the
occur
Islands duct
example,
from 25
to
68
figure
duct.
km
is
31
For a
quite
located well within the skip zone.
can conclude
affect will
receiver
For
m thick surface-based
receiver of 19.2 m, the skip zone evident, with
3
over
that
surface-based
ducts
are not
propagation loss in this case, even though about
area
height
11
percent On
through
1 143
the the
of
the
other range
time hand,
(figure
29)
varying
of expected
in the
values
I I (figure This
32),
shows
that propagation loss will vary substantially.
is particularly true
for the higher
I
I i I U
frequencies.
I to-
TRAM HT 4.8 NO. OF RAYS 10 HIN ANG deg -18 MAX ANG deg 18 REFLECTED RAYS V PROFILE CHARACTERISTICS
88H
E G
DUCT BTM m
H3
0
T 48-
2-
e( height =19.2 m range = 35.2 km
~I -8
16
skip zone - -m
32
48
64
88
RANGE km Figure
31:
i
RAYS display for the frequency and geometries
in the
Greek Island experiment under surface-based ducting conditions.
144
1 5
o188-
FEQ
P R 0 P 120A G A
fHz
9688
POLARIZATION HOR TRA HT n 4.8 REC HT m 19.2 ANT TYPE a 091I VER BY deg W/A ELEV ANG deg W/A
receiver range 35.2 km
6 8 1.49 NSS 334 ABS HUM g/m3 7.5 WIND SP kts 12.5 E140--EVD HT m
1
SBD HT
=
0 I N 168L 0 S S 188-
6 n EUD HT 4 nEVD HT 2 a EVD HT
n
0 P EUD HT
d B 288-,II
8
18
28 RANGE
Figure Greek
3
32:
PROPR display
Island
48
FREE SPACE----
the
under
Table evaporation
frequency and geometries
multiple
evaporation
2 shows duct
the
propagation
height
for
the
loss four
from
of the
ducting
PROPR-versus-
frequencies
corresponding geometries with a * indicating duct heights those
recommended
in section 6.0
for
I U I 3
58
environments.
I *
experiment
for
38 km
145
use
in PROPR.
and
beyond
I I Table
2:
Greek Islands
duct height
for the
geometries
described.
IEVD
HT m
frequency bands
and
duct heights beyond those
I I
J
Ku
X
S
0
-I --------.-------- ---181.9 172.9 152.9 I 161.7
2
152.5
j 161.6
166.1 I
168.1
4
152.3
I 160.5
161.8
157.3
6
151.9
158.9
154.0
146.0
8
151.4
157.4
146.8
145.1
10
151.
155.3
139.7
155.8
12
150.7
152.2
140.2
166.1* I
14
150.4
148.4
143.5
172.6*
16
150.1
145.1
148.3*
172.6*
18
149.9
142.3
152.0*
172.6*
20
149.2
139.4
154.7*
172.6*
22
147.8
136.4
155.8*
172.6*
24
147.1 I
135.1 i
153.3*
172.6*
26
145.4
133.9
153.3*
172.6*
28
144.4
133.7
153.3*
172.6*
30
143.8
134.2
153. 3*
172.6*
32
142.7
135.8*
153.3*
172.6*
34
141.2
137.0*
153.3*
172.6*
36
140.0
138.1*
153.3*
172.6*
38
139.0
139.1*
153.3*
I 172.6*
40
1 137.6
I 140.2*
153.3*
I 172.6* J
.
Comparing height distribution be
experiment
indicates
I
L
.-----------
statistical
*
A
from PROPR-versus-evaporatilon
in PROPR.
recommended for use
will
loss values
Propagation
the
duct heights
of figure
assessments
questionable
from
29 indicates
of propagation loss at
X
and
146
Ku
table that at
bands.
3 I
3 I
3 I
I
I
2 with the EREPS
can yield
L and S bands, The
duct
most
but
useful
3 5
statistical
presentation
is
often the
accumulated
distribution of propagation loss, which can be determined
from figure
propagation loss
will
29
and
table
frequency
quite
easily
2. For example, at L band,
always exceed 130 dB.
Propagation
loss
greater than 140 dB occurs for duct heights less than 36 m, which from figure 29 is 99.6 percent.
3
150
dB
corresponds
percent.
to
duct
Propagation heights
less
loss
greater
than 17
m,
or
than 75.2
The accumulated frequency distributions thus determined
are presented in table 3 for all four frequency bands. Also shown
Iare
the observed
distributions
as
given by
Richter
and Hitney
(1988).
U
3
Table
3:
height
distributions and as observed for all seasons measured at
Percent of time propagation loss is exceeded for the Greek Islands experiment as calculated by EREPS from annual duct each frequency band.
3
Loss) dB
Geometries as stated in text.
I
L
) EREPS
OBS
S EREPS
I
X
I EREPS
OBS
Ku OBS
I EREPS
OBS
120
100.0 100.0
130
100.0
95.8
140
99.6
89.5
84.6
65.3
150
75.2
64.5
40.1
39.3
41.6
38.5
81.3
70.5
II170
0.0
9.5
8.8
3.9
7.1
4.7
64.5
27.3
7.1
3
160
1
I
100.0 100.0 i100.0 80.6
I
100.0 100.0 i100.0 94.3 83.6 74.1 i
I100.0 100.0 I100.0 100.0 100.0 98.9
0.0
0.0
0.0
0.0 I
1.0
0.9
I48.8
180
0.0
0.0
0.0
0.0
0.0
0.0
0.5
0.8
1190
0.0
0.0
0.0
0.01
0.0
0.0)
0.0
0.1
Examination calculations
are
in
of
table
3
reasonably
shows good
that
L,
agreement
S,
and X band with
the
observations, but Ku band calculations indicate substantially higher propagation loss values than were observed. This
I
147
I i disagreement is due to the frequent occurrence of duct heights in Marsden Square
142
EREPS at Ku band.
that
Note
are beyond
the
recommended
limits of
that X band agrees quite well in spite of
some duct heights occurring beyond
the
recommended limit.
For
applications in other areas where duct heights are predomuinantly low, such as in the North Atlantic Ocean, the EREPS assessments would prove to be good even at the highest frequencies.
There
is
a substantial
3
reduction
in propagation loss attributable to the evaporation duct when compared to diffraction levels without an evaporation duct.
For example,
figure 30 shows
that at X band the diffraction propagation loss is 173 dB and the free-space propagation loss is 143 dB. Interpolation of table 3 shows the propagation loss exceeded 50 percent of the time is 148 dB.
Thus,
the evaporation duct has resulted in a signal
improvement
of
25
dB
You should this
strength
over diffraction with the median observed
(or calculated) propagation loss much closer to diffraction. note
that
to
similar methods
free space
as
those
U 1
than
U
used in
example may be applied to maximum detection, communication,
or ESM ranges. You would employ PROPR to determine maximum range versus duct height and then use the duct height distributions from SDS PROPR or
to compute distributions of maximum range. PROPH could be used
In addition,
to estimate
frequency distributions
of propagation factor, or signal-to-noise
ratio over a particular
3 U
path.
148I
I
I
I
a 9.0
Glossary The
following
within the
is
a glossary of
document.
all equation FFACTR
When appropriate,
-
24).
3
U
direct ray launch angle in radians.
(see figure
Also used as attenuation rate in NOSC
evaporation duct model. (6371)
[alpha]
in kilometers.
a
-
earth radius
ae
-
effective earth radius
A
(k x a) in kilometers.
calculation. resolution cell
in dB.
Ac
-
area of radar
i
Ae
-
antenna effective aperture.
3
A
-
wind speed factor within the clutter model.
8
-
reflected ray launch
angle
figure 24).
Also used as scaled
I
[beta]
in radians.
(see
attenuation rate in NOSC evaporation duct model. BW
-
transmitting antenna's beamwidth [bwidth - degrees;
c
-
speed of light a constant
A
-
dMdh -
I
[ae]
a constant within the antenna pattern factor
-
£
3 3
code
source [].
variable names are enclosed within brackets, i.e., a
symbols used
in radians.
antbwr - radians]
(3 x 108 m/sec).
Also used as
in the antenna pattern factor.
scaled evaporation duct height in meters.
[del]
modified refractivity gradient in M per km.
149
I 1 D
-
divergence duct height
D
visibility
6
path-length
factor.
[divfac]
Also
surface-based
in meters.
factor within the
difference between direct and sea
reflected rays
in radians.
evaporation duct height
Also used as
in meters.
-
ordinary dielectric constant of
Ei
-
internal
e
-
ambient water
E
-electric
E
-
electric field conditions.
F
-
propagation factor.
[ff
Fzr
-
receiver height-gain
function within
angles
-
in figure
vapor pressure
[eps]
24.>
in millibars.
duct
transmitter's Gigahertz.
5
strength under free-space
duct model.
the
frequency
NOSC
[fzr]
model.
I 1 3 3
transmitter height-gain function within evaporation
f
sea water.
field strength at a point.
evaporation -
as seen
3
[delta]
4
Fzt
3
radar model.
3
the NOSC
[fzt]
in Megahertz
or
3
[freq]
fp
-
pulse
repetition
-Y
-
angle
shown
frequency
in figure
150
24.
in Hertz.
[gamma]
3 3
1 1
I I I r
factor within the NOSC evaporation duct
-excitation
model.
3
[tim]
G
antenna gain
h0
effective
in dB.
scattering height within the
troposcatter model.
i!
=
scale
factor
for
[hsubO]
natural units
standard diffraction model.
SH
a
H0
absolute humidity
frequency gain model.
3 3
of height
[fqterm)
in grams per
cubic meter.
function within the
[hO]
height
of receiver/target
Ht
height
of
h
root-mean-squared wave height
k
effective earth
I
A
wavelength
3
L
propagation
loss
Ld
diffraction
field antenna pattern loss,
of how much
energy
horizon.
I
[
[humid]
troposcatter
Hr
I
in
Lf
radar
Lfs
free-space
in meters.
[hr]
transmitter antenna in meters.
radius
factor.
[ht]
in meters.
[hbar]
[rk]
in meters
in dB.
is
radiated toward
[exloss]
target
fluctuation loss
path
loss
151
in dB.
in dB.
a measure
the
I I I Ls
-
miscellaneous system losses
M
-
modified
N
in dB.
refractivity.
refractivity
N
receiver
-
N
-
number
m
noise
of
factor
pulses
in
3 3
dB.
integrated
within
the
radar
model.
NS
n
lim
-
surface
=
in
-
complex
index
of
refraction.
-
grazing
angle
in
radians.
-
grazing angle [psilim)
-
reflection
coefficient
phase
shift
subscripts
C,
stand
for
refractivity
arbitrary
horizontal,
value.
U
[nsubs]
angle.
m
and
(see
in radians,
limit
H,
3
and
V
vertical
antenna
figure
Reed
24).
[psi]
(1966).
where
3
circular, polarization.
3
[phi]
-
angle the
0h
-
3
betweena
upwind
antenna
the
radar
direction
horizontal
antenna
boresight
and
in degrees.
scan
rate
in
3
revolution-per-
minute.I P
-
a
constant
within
the
antenna pattern
factor
3
calculation.
I 152
I
I I
3 3
P
-
power density in Watts per square meter.
P
-
clutter power in dB.
Pd
-
probability of detection in percent.
Pn
-
noise power in dB. power transmitted in Watts.
Pt
P
-
power received
p
-
a scaled range within the evaporation duct loss.
I
r
-
ground range in kilometers
3
rI
-range
r2
-
3
-
figure 24).
[rI]
[rl]
(see figure 24).
range from reflection point to receiver/target in kilometers.
rd
(see
from transmitter to reflection point in
kilometers.
I
in Watts.
fr21
(see figure 24).
range to start of diffraction field in kilometers [rsubd]
5
[horizn]
rhor -
horizon range in kilometers.
R
reflection coefficient magnitude where subscripts
-
o, C, H, and V stand for smooth
'irface,
circular, horizontal, and vertical polarization. [rmag] RN
3
I
-
scale
factor for range
duct model.
I
[rfac]
153
in the NOSC evaporation
I U I R
-
RH
-relative
Rfs
-
a
scale factor for natural units of range in standard diffraction model. [fterm]
3
humidity in percent.
radar free-space range
in kilometers.
conductivity of sea water.
[sigma]
Also target
radar cross section in square meters. ao
-average
(7
-
surface
clutter cross section per unit area in
roughness parameter within the clutter
model. 8
total path-length difference,
3
in radians,
between the direct and sea-reflected rays including the phase [theta]
lag due
to reflection.
Also used as a scattering angle, in
radians, within the
troposcatter model.
8H
-
horizontal beamwidth in radians.
S/N
-
signal-to-noise ratio
-
pulse width
in dB.
in microseconds.
Also the compressed
1 3
pulse width in seconds. T
-
temperature in degrees Kelvin.
Also used as a
U
threshold level in the ESM models. U
-
height-gain functions
in dB.
[fzt or fzr
for
evaporation duct transmitter and receiver respectively.
fofz for surface-based duct]
154
I
I I I I
3
V
-
attenuation
W
-
antenna
W
-
surface wind velocity
in meters per
x
-
a constant within
antenna pattern
z
-
an arbitrary height
Z
-
scale
factor
in dB.
pattern normalization factor.
factor
the
second.
factor.
in meters.
for height within
evaporation duct model.
I U I I I I U I I
I 3
[tlvx]
155
fzfac]
the
NOSC
[wind]
10.0
References
Ament, W.S., Proc.
"Toward a Theory of Reflection by a Rough
IRE, vol.
Barrick, D.E. , sea,
I m I U
2,
application
Bean,
B.R.
vol.
and
Publications,
470-483,
1961.
F.A.,
McGraw-Hill
D.C.
E.
Proc. pp
Range
IEEE, vol.
M.M., IEEE
6-10,
F.B.
in
Inc.,
Geneva,
no.
Dyer
2,
Radar
3
Dover
I
Scattering of Microwaves AP-9,
pp.
3
Meteorology,
Vertical-Plane 7098,
Coverage
25 June
Lexington
1970.
Books,
1980.
m
Media",
Vol.
V,
Recommendations International
and
Radio
Radio
K.D. Anderson, and G.B.
Propagation
Assessment",
1985.
"Radar
Sea Clutter Model",
Conference on Antennas 1978.
I
I
R.A. Pappert,
Feb
vol.
Handbook of
Analysis,
and M.T. Tuley,
November
sea",
1986.
"Tropospheric 73,
the
New York, 1945.
1986,
Richter,
rough
Meteorology,
Propagat.,
N.R. Beers,
Non-ionized
International
London,
Antennas
Performance
CCIR,
J.H.
Baumgartner, Jr. ,
Radio
Incoherent
Plotting of
Committee,
Hitney, H.V.,
Horst,
and
above
a
1968.
Lexington, MA.,
the
Consultative
Proc.
Trans.
across
3
1971.
Research Laboratory Report
"Propagation of
VHF propagation
527-533,
and
Book Company,
Naval
and
York,
Bollay,
L.V. , Radar
Reports
1953.
Dutton,
New
IRE
Heath & Co.,
CCIR,
pp.
E.J.
L.V. , "Machine
Diagrams",
Blake,
HF
C.I. , "Coherent Ocean",
Blake,
142-146,
to
6,
Inc.,
from the
Berry,
pp.
"Theory of HF and VHF propagation
Radio Science,
Beard,
41,
Surface",
I
3
and Propagation, m
156
I Jeske, H.,
3
"Die Ausbreitung elektromagnetischer Wellen im cm- bis
m-Band ueber
dem
Meer
meteorologischen Hamburger
3
3
Kerr,
Beruecksichtigung der
besonderer
unter
Bedingungen
in
der
maritimen
Grenzschicht",
Geophysikalische Einzelschriften, Hamburg,
D.E.
Company,
Propagation
Inc.,
Nathanson,
of
Short
Radio Waves,
1965.
McGraw-Hill Book
1951.
F.E.,
Radar
Design Principles, McGraw
Hill,
New York,
1969.
3 1
Patterson. W.L. ,
C.P.
Anderson, and G.E. September
1151,
Hattan, H.V.
Lindem,
"IREPS
Hitney,
3.0 User's
R.A.
Paulus,
Manual",
K.D.
NOSC TD
1987.
Paulus,
R.A. ,
"Practical
model",
Radio
Science,
application
vol.
20,
of
no.4,
an
pp
evaporation
duct
July-August
887-896,
1985.
U
Phillips, Press,
3
Reed,
O.M. , Dynamics
London,
H.R.
and
P.L. ,
"Transmission
3
Circuits", Bureau
C.M.
Russell,
Publishers,
A.G.
Longley,
1 &
of Standards,
and
2,
U.S.
3
the
K.A. for
H.V.
2, Jan
University
and
101,
of
Propagation,
1966.
Tropospheric
Department
A.P.
Barsis,
Communication
Commerce, National
1965.
Hitney, "Antenna Heights for the Optimum Evaporation
1988.
1 m
MA.,
Norton,
Mediterranean Measurements",
TD 1209, vol.
Cambridge
High Frequency
Cambridge,
Technical Note
Utilization of the Oceanic from
Ultra
Inc.
Predictions
Loss
vols.
Richter, J.H.
the Upper Ocean,
1966.
Boston Technical
Rice,
of
157
Duct, Naval
Part
III:
Results
Ocean Systems
Center
I Yeh,
L.P.
IRE Trans.
,
"Simple Methods for Designing Troposcatter Circuits", GS-8,
pp.
193-198,
1960.
I
U U I U U I I I I I I I I I 158
5
U
Appendix A
I
3
The following EREPS products fro PROPR, PROPH, COVER, RAYS, and SDS illustrate a variety of features available from each program. Each sample was generated with an EGA-equipped computer and a LaserJet Series II printer with 1 Megabyte of additional memory using the GRAFLASR program supplied with This combination of GRAFPLUS from Jewell Technologies, Inc. hardware and software yields a resolution of 300 dots per inch.
II I I I I I I I I I lA IA
I I Sanple Standard and Ducting Conditions
FREO
e8P R
Mz 5688
POLARIZATION TRAN H ft
0
Optical Region
REC HT
P 110-
A380-t
Surface-based Duct
VER BUJ
A T 14 N............. ........-......
.......
75 SIW
deg
EVDHT
I-
NO 75
ft
ANT TYPE
18
asnoted
SBD HT as noted SBS339 1.333
- "....K
178-
ABS HUll
L
g/n3
7.5
UIND SP kts 13-n Evaporation Duct
d B
or d THRESHOLDS ---- ---i 188 Mi............. i 28 -n i 300 408
Troposcatter 238-9---nn8
8
28
48
68
880
188
RANGE nni
FREE SPACE
ESfl Intercept Range versus Evaporation Duct Height
28FREQ
POLARIZATION
R O
TRAN HT ft NEC HT ft
Mlaximum EMt Intercept Range for 12-n Evaporation Duct Height
ELEV NG deg T 1681 I 0 N
EVD HT SBD HT K
L
------84
0
---------
8
S
--------------------
1
12,
/ANTCGN
2
S 28-
Evaporation Duct Heights
dI B
9.2 HON
75 75 8
as noted m a 1.333
NSUBS
188 -------
9
ANT TYPE GAUSS BU deg 3
=VEN
-
----
GHz
P
P 148A
10
FREE-SPACE RANGE
S 2881
339
BS HUl g/n3 7.5 UIND SP kts 8
PK POWJ
MI
dli
SYS LOSS dB ESH SENS dn
188
38
18 -88
FREE SPACE -
220 8
48
88
128 RANGE nni A2
168
I
ES11 INTERCEPT 200 THRESHOLD -------PROPLOSS dB 188.8
[
i I m 2 P 2-
S-Band Radar, Standard Atnosphere, 18 Knots Mind
A P--------
-
---
-
-----------------
TPK 1 -20-
ANT SYS REC HOR PRF
N Radar Detection Threshold F -40A 0 6-RCS R
5
is RANGE
15
e 285 1.3 38 6 6
FS RANGE kn 34.9
S 40-
N
I
20-
N
I
"
o
-_
'Evap ,./
----
----
-n Duct 3ANT
lte -;-_.7
--
---
S 13-n TargetEvaDct
E
1Hz 5688 FRED HOR POLARIZATION 25 uRADR T"]RCHT T HT HT n n SINX/X ANT TYPE 18 VER BU deg 0 ELEVARNG dg 285 PK POW kW P WIDTH us 1.3 1.3 COIP PI us GN dli 32 8.4 SYS LOSS dB REC HF dB 14 HOR BW deg 1.5 658 Hz PRF RT rn SCAN 15 RCS
-20B
t.AmPD
lte
m -4018 *
GN dBi LOSS dB NF dB BM deg Hz
3
25 THRESHOLD --------
20
kn
C-Band Radar Target S Clutter S/N Ratios Mind Speed: 15 Knots
60-
A L
SINX/X
SPFA
d BFREE
S 1 C
deg
1.5 1888 SCAN R rpn 15 SIM I .9 PD 1.8E- 8 SMICASE 1-FLCT SPACE
C
I
AT l TYPE
ELEV ANG deg PON kM P WIDTH us
A
I
11Hz 3888
POLARIZATION HO RADR HT ni 25
Free Space Reference
R 0
FRED
20
38 RANGE km A3
48
sqn
.1 8.5 1.8E- 8 1-FLCT
PFA SU CASE DET FACTOR ---58 CLUTTER --------FS RANGE kn 15.1
N U Over-The-Horizon 500-FM ES1 Interception
4 H E
POLARIZAT ION HOR 75 TRAM NT ft 58 nni RNGE 0"I ANT TYPE W/A3 VENUBM deg EL AG deg W/A
Numbers for curves indicate evaporation dukct height in neters
4W
:EVD
1
C H
HT
asrnotedi
SBDIH7 K
8 1.333
AS HUM g/n3 7.5
288-
MIND SP
f
188-
12
,\
FREE SPACE
8 238
200
I 118
V' 14 178 PROPAGATION LOSS dB
FRE
Optical Region IELEV
H E Diffraction
13-m Evaporation
j-L
*
Duct
f t
100-ti SurfaceBased Duct
58-
"k~5600
400
,
488
----- nn i 238
288
148 PROPAGATION LOSS dB 178
A4
33
FREE-SPACE RI GE or dB THUEHOLD to -nni ...... nni 2
I
Troposcatter
-
-
as noted EVD HT as noted SBD HT 1.333 K 339 NSUJBS ABS Hll g/n3 7.5 18 MIND SP kts
W
18-
-
HOR 75 TRAN HT ft 5 RANGE "nni (XI ANIT TYPE N/A VERBM deg ANG deg NWAI
*POLARIZATION
2088-
-
ES INTERCEPT 80 THRESHOLD PROPLOSS dB 188.8
250Sample Standard and Ducting Conditions 258
18 180 38 18 -88
kts
PK PON Wid dBi ANT dB SYS ss 4Sdm ESH SEW
t
H T
I
339
NSUBS
1
E
I
Mz 92o
118
88
FREE SPACE
--
-
-
U
3
I
C-Band Radar Target A Clutter S/N Ratios Wind Speed: 15 Knots
189-
FRE 1Hz 5M POLARI2ATION HOR
IRADN
H E I G
80- Clutter for standard conditions
Clutter for 13-n evaporation duct
__ I
Detectibility (noise)
Ifactor
TSYS
is Note: This• noise limited for standard conditions, clutter linited for the ducting
28but
20-
1.3
CoIIP PU
us
1.3
LOSS dB
8.4
condition shown.
I-
I
8
20 -to SIGHNLOIS£ dlB
-40
II
-13-n
evap 1" duct 58
I
Detection Threshold
8I8 I
H
Free Space
Reference
REC IF HOR BU PRF SCAN NT RCS
FRED
N&
POLARIZATION
ELEV AMG deg
IOR
Wi us
dli ANT CH SYS LOSS dCi F dB
40-REC
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PRPGTO3ATRd A5
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Hz rpm am
1999 15 I .9
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RADR HT n kn RANCE SINX/X ANT TYPE 3 VER M deg PK POU P MID"H
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dB deg Hz rpm sqm
86 CUJTTER ----------15.1 FS RANGE kn
S-Band Radar, Standard Atmosphere. 28 Knots Uind I
188
3
14 1.5 658 15 .1 8.5 PD PFA 1.8E- 8 1-FLCT SU CASE 1 DET FACTOR -. . . .
std i-70
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us
CHdi
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40-
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n
P UIDTH
,'PKPU 60-
H
I
:
HT
ki 15 RANGE SIN/ NiT TYPE VER MU deg 16 0 ELEV NG deg
SU CASE I-FL.CT FREE SPACE -... 40 THIRESHOLD ---------
FS RANGE km
34.9
I UHF Radar Coverage in Standard Conditions
MHz
425
POLARIZATION TRA HT ft
HOR 75
TYPE VERBM
"I14 W/A
ELEV ANG
WA
5k -FREQ H 0kANT E S38k .. .i .....
H H T f
28k
"-,
m a 1.333
SBD HT '-.K ABS HUll 9/n3 MIND SP kts
18k 8
E D HT
I
7.5 18
FREE SPACE RANGES 8
48
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.
or dB THRESHOLDSI
6
128 16
nni
188
11Hz
458 HOR
Im
288 RANGE neI Range Extension from a Surface-based Duct H
2588
-
-R
POLARIZATION HT ni
E 08TRAN Standard Atnosphere
I
SVERBU H
25 SINX/X
ANT TYPE
deg
18
ELEV AnH deg
588
8 -'
8 8
T 1888HT
m
8
48
"
as noted SBD HT 1.333 • ", ,,, ', "ABS HUMf g/a3 7.5 18 MIND SP kts 300-m Surface-"I
%-based Duct
88
RANGE km8 A6
FREE SPACE RANGE3
%I
U I
U Effects of Frequency Diversity
18k . ....... -- H-E I G 6k H* 1 H 4k
1350 M z 908 MHz
Tf,
t
2k
ABS HUM 9/n3 7.5 18 MIND! SP kis
-
FREE SPACE RANGE
*
|
88
if
188
RANGE n i Radar Perfornance versus Radar Cross Section 5888 ----------------------
MHz 3888 FREQ POLARIZATION HOR 68 RADR HT ft GAUSS ANT TYPE VER BU deg 6 8 ELEV ANG deg
i =18 s 480 --------------.-.... H E
PK POU P MIDTH
I 3000 -------------
C
GN
=1smANT
H
SYS LOSS REC HF HOR B PRF SCAN RT RCS PD PFA SM CASE
T 2000 i
I=.1 sqn 8
I
3A7
as noted FRE HOR POLARIZATION 68 TRAM HT ft SIHX/X ANT TYPE deg 6 VER B 8 ELEV ANG deg 8 EVD HTSB HT 0 SD H 0 K 1.333
188 RANGE ki8
kW us
d~i
1888 1
38
6 dB 5 dB 3 deg Hz 1888 15 rpn as noted .9 1.8E- 8 I-FLCT
U Sanple Surface-Based Duct TRJA H ft
18888-
18
503
NO. OF RAYS
HIM AMG deg XANG deg REFLECTED RAYS
80-
-2 2 V
PROFILE
H E I
HEIGHT(ft) Dietad0 Reflected Rays
68008-
see 1886
G
2808
H
Il-UNITS 350 382
3
338
368I
T 48008-
t Trapped Rays
200801
0I
a1029
:
169
206
RANGE nni Sanple Elevated Duct at 5000 ft
TRAM HT ft NO. OF RAYS
10008-
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flected a
8000-
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608-
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We"
C H T
DUCT TOP ft
5388
DUCT ETH ft LVR THK ft
4588 308
a LYR TOP ft 8 LYR BTH ft None LYR TYPE GRD Hilft None
40Wf t 2LYR
LYRTOP ft LYRDTH ft LYR TYPE
RANGE ned 8A8
3
0 0 None
LVI CRD Il/kft None
076-
I
I
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Elevated Duct at 58880
1
i
608
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H
i
TRAM HT: 5080 n
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A __________I___deg___
MUnits
RAG km Altitude Error in a Surface-Based Duct
I
18888-
H 1 600 G488 H T
color indicates
.,Ray
err
200
I
208
388
RANGE km *
MO.OF RAYS MINANG deg
288 -3
It.Error (m)=
4000-
188o
188
3 MAX ANC deg REFLECTED RAYS N/A PROFILE HEIGHT(m) M-UNITS 358 8 385 388 338 401 1886
8888-
IE
TRAM HT m
A9
488
588
288 488 688td e 888
1288 1488
168* 1888
I
90
0-[
68
60
3 .38 00
30
_ _.__1_
30 -ORLD aso
6" 188 128 CROSSHAIR LOCATION
EVD HT
-TO 80TO2
-- >
68 8 25 N 25 U flSQ: 75
% OCCUR 8
10
15
2.1
4 TO 6 n
5.0 VI
E
6 TO 8 n 8 TO 10n 10 TO 12n 12 TO 14n 14 TO16.
7.0 9.5 11.8 13.3 12.7
P 0 R A
16 TO 18n
11.8
T
8.7 6.3 4.3 2.6 1.6 8.8 8.5 8.2 8.1 8.1 8.80 a__I_ 8.
68
28
128
25
18I
ANNUAL SURFACE DUCT SUMMARY
2 TO 4 n
18 TO 28 n 20 TO 22n 22 TO 24 n 24 TO 26n 26 TO 28n 28 TO 38 n 38 TO 32 m 32 TO 34 n 34 TO 36n 36 TO .8 n 38 TO 40 )48
5
---. 3-2.3
68
AVERGE..
SURFACE OBS: AVERAGED
6 SQUARES
AVG EVD HT: AVG MIND SP:
14. 1 n 13.0 KTS
________
I 0 H
UPPER AIR DES: RS 8594 SAL (CABO VERDE),I PORTUGAL
D U C T
LATITUDE: 16.73 N3 LONGITUDE: 22.95 U SBD OCCURRENCE: 15.8 % AVG SBD HT: 186 ii AVG NSIJBS: 349 AVG K: 1.83
H T _____
A10
SAIPLE SIZE:
1683
I %OCCUR8
IEVDHT
5
18
15
28
25
SURFACE DUCT SU MMIA RY
------ - -- -
8 TO 2
8.7
2 TO 4TO 6 TO 8 TO
4n 6n 8mn 10 m 18 TO 12 n 12 TO 14 n 14 TO 16 m 16 TO 18 n 18 TO 28 n 28 TO 22 m 22 TO 24 n 24 T0 26 m 26 TO 28 m 28 TO 30 m 38 TO 32 n 32 TO 34 m 34 TO 36 361 i36n 38 TO 48 40 n
8.6 2.8 4.3 5.7 9.8 11.4 12.6 13.3 11.8 18.8 7.1 4.8 2.8 1.6 8.8 8.4 8.2 8.1 8.8 8.8
E V A P 0 R A T I 0 H
80TO 2n
SURFACE OBS: HS 28 0 O18H LATITUDE: LONGI TUDE: 88 TO 98E AVG EVD HT: 16.5 n 12.1 KTS AVG MIND SP: SAMPLE SIZE: 53832 OBS UPPER AIR OBS: RS 43466 COLOMBO, CEYLON
D U C T
6.98 H LATITUDE: LONGITUDE: 79.87 E SBD OCCURRENCE: 18.8 % AVG SBD HT: 94 m AVG NSUBS: 387 1.71 AVG K: SAMPLE SIZE: 192
H T
*EVD HT % OCCUR 8 --------------- -----
5
18
15
28
25
I
I
I
I
O TO0 12 n 12 TO 14n 14 TO 1G m 16 TO 18 m 18 TO 28 m
SURFACE OBS: MS 252
22.4
A
8. 8.8
N
26 TO 28n
0.6
D
30 TO 32n 32 TTO 34
8.8 C
88
4
n
LATITUDE:
68 TO 78 H
AV D H'T. 6.7 n AVG MIND SP: 17.9 KTS SAMPLE SIZE: 121114 OBS
10. 0 4.8 R 1.4 A 8.4 T 0.1 1
22 TO24n 24 TO26n
36 TO38
ANNUAL SURFACE DUCT SUMMIARY
8.9 2 TO4n 1.
6 TO 8 a
ANNUAL
UPPER AIR OBS: RS
1241
ORLAND, NOWAY
LONGITUDE:
9.43 E SBD OCCURRENCE: 1.8
0.9
T .0 H--
AVGHSUBS: AVG K: SAMPLE SIZE:
9.0 .8 .n All
317 1.33 3188
I U I Appendix B
Subroutine:
FFACTR
Date:
02/01/90
Process: For
electromagnetic
systems,
computes
the
pattern propaga-
tion factor in decibels for a specified range. Positive values indicate a signal level above the free-space field strength. Negative values indicate a signal level below free-space field strengta.
I
Subroutines: antpar antpat dconst difint dloss gtheta hgain opconst opffac opticf oplimit rliter ref ruff sbd skipzone
Functions: FNAMAX FNAMIN FNUZ
QuickBASIC functions abs atn cos exp log (natural) sin sqr swap tan
3tropo When calling subroutines within FFACTR, convention is to use lower case variable names for the input parameters and upper case variable names for the returned parameters.
I I I
B
I I Input S
parameters:
Electromagnetic
antyp$
system:I
-Antenna OMNI
type -
Omnidirectional
freq
-
hr
-
SINX/X - SIN(X)/X GAUSS - Gaussian beam CSC-SQ - Cosecant-squared HT-FINDER - Generic height finder Antenna beam width (0.5 - 45.0 degs) Antenna elevation angle (-10.0 to +10.0 Oo is horizontal normal pointing angle shipboard radar systems Frequency 100 - 20000 MHz Receiver/target height (1 - 10000 m)
ht
-
Transmitter
polar$
-
bwidth elevat
-
-
degs) for
I I
antenna height (1 - 10000 m) one of the above terminal height should be < 100 m for pulsed systems Antenna polarization H - horizontal
V - vertical r
-
C - circular Desired range for
F-Factor
(1
-
1000
km)
3
Environmental: delta humid
-
-
Evaporation duct height Absolute humidity (0
(0 14
-
40 m) grams/m^3) -
World average is 7.5 grams/m^3 Effective earth radius factor (1.0 4/3 is a "standard" atmosphere
rk
-
rnsubs
-
sbdht
-
World average is Surface-based duct
wind
-
Surface
Surface
refractivity
(0
-
-
5.0)
U
450)
339 N-units (0 - 1000 m) height wind velocity (0 - 100 KNOTS)
U
Output parameter: ff 20*LOGlO(Pattern propagation factor) in dB ff values that are positive indicate a signal level above the free-space field at that range. Negative values indicate signal levels below the free-space field.
I B2!
I U The, following program is a demonstration driver for the FFACTR subroutine. It is included to show possible uses for the FFACTR subroutine. The FFACTR subroutine is structured to return a value (in dB) representing the ratio of the actual field strength at a range, to the free-space field strength at that same range. Because the FFACTR subroutine may be called in any arbitrary fashion, it is not the most efficient structure for producing a product such as a lossversus-range (or height). If only the range is to be varied, with constant terminal heights, a zommom application, the OPCONST and the DCONST subroutine calls should be made only once at the start of the application program. This would necessitate removing them from tI.e FFACTR subroutine and placing them in the calling program. Three sets of input parameters and resulting pathloss and propagation factors are provided below for testing of this subroutine after a language conversion. This demonstration program calls FFACTR only with the first input set:
I
Set I input parameters Enivronmental: Delta = 0.0
*
and
output values - standard Electromagnetic system: Antype$ = "SINX/X"
Humid
=7.5
Bwidth
= 2.0
Rnsubs Rk Sbdht
=
Elevat Freq Hr
=
Ht
- 20.0
Polar$
=
Wind
=
=
339.0 4./3. 0.0
= 10.0
Range (km) 55.0 50.0 45.0 40.0 35 0 30.0 25.0
Propagation 183.81 175.91 168.34 160.65 152.83 144.83 136.59
20.0
(dB)
=
0.0
'
I
"H"
Propagation -41.59 -34.52 -27.86 -21.20 -14.54 7.88 1.21
|I3
factor
4.03
and output values - lOm evap Electromagnetic system: Antype$
-
Bwidth Elevat
- 4.0 - 0.0
Freq Hr Ht
-
-
9600.0 100.0 10.0
Polar$
-
"V
B It
=
0.0 5600.0 20.0
129.41
Set 2 input parameters Enivronmental: Delta = 10.0 Humid = 7.5 Rnsubs 339.0 Rk = 4./3. Sbdht - 0 0 Wind
loss
=
atmo
"CSC-SQ"
duct
(dB)
I I
I Range (km) 55.0 50.0 45.0 40.0
Propagation 145.28 143.66 141.96 140.14
(dB)
Propagation factor 1.63 2.42 3.21 3.99
35.0
140.90
2.08
30.0 25.0 20.0
142.73 137.51 133.03
-1.09 2.54 5.09
Set 3 input parameters Enivronmental: Delta - 10.0 Humid Rnsubs
Rk Sbdht Wind
= = =
Bwidth Elevat
=
=
4.0 0.0
Freq
=
400.0
=
2.1 100.0
=
50.0
=
20.0
Hr Ht
=
Polar$
=
10.0 "C"
Propagation loss 110.61 115.61 120.61 125.61 130.61 127.63 123.65 119.31
demonstration
defint i-n const Pi -
(dB)
I 3
and output values - lOOm sbd Electromagnetic system: Antype$ - "GAUSS"
7.5 339.0
Range (km) 55.0 50.0 45.0 40.0 35.0 30.0 25.0 20.0
Start
loss
(dB)
Propagation 8.69 2.86 -3.05 -9.08 -15.24 -13.59 -11.19 -8.80
I I 3
factor
(dB)
program
3.14159
const
revision$
=
"I.00"
const
rev.date$
-
"01
FEB
1990"
B I I l
/comffactr /comffactr
common shared common shared
1common Ucommon Icommon Ncommon
shared /comffactr common shared /comffactr common shared /comffactr common shared /comffactr shared /comffactr common shared /comffactr common shared /comffactr common shared /comffactr shared /comffactr
/comffactr /comffactr /comffactr shared /comffactr
common shared common shared common shared antyp$ bwidth
I
ht
/ae, ae2, aeth, alpha, antbwr /antelr, antfac, antyp$, atten /bwidth, ci, c2, c3, c4 ,c5, c6, c7 /del, delta, difac, dtot, elevat /elmaxr, exioss, f3, fofz, freq /fsloss, fsterm, fterm, hi, h2 /hl4pil, h24pii, h24ae2, hbar /hbfreq, hdif, him, hmini, horizn /horiznl, hr, ht, humid, opmaxd /opmaxi, patd, patrfac, polar$, psi /rilim, rlmin, rk, rmag, rmax /rn2.imag, rn2.real, rns2, rnsterm /rnsubs, rsbd, rsbdloss, rsubd /sbdht, tfac, thefac, tsubl, tsub2 /twoae, wind, wv.atten, zfac
"SINX/X" 2 .0
= =
20 .00
=
polar$-"H delta humid
0.0 0
77.5 4./3. rnsubs - 339.0 sbdht - 0.0 wind - 1.0.0 fsterm - 32.45 dr 5 5.0 rk
I
r
-
+
8.686*LOG(freq)
-60.0
f or
i r
to
I -r
-
8
dr
call
ffactr(freq,ht,hr,polar$ ,antyp$ ,bwidth,elevat,delta,_ sbdht ,humid, rk, rnsubs ,wind, R, FF) rloss = fsterm + 8.686*LOG(r) - ff print r,rioss,ff EDnext
3
'
i
End of demonstration
program
B5
I
I NOSC defined functions DEF FNAMAX(eleml,elem2) function to find maximum of IF eleml >IF eleml < END DEF
elem2 THEN elem2 THEN
END
DEF
DEF
FNU(z) function
two
3
constants
elem2 THEN FNAMIN - eleml elem2 THEN FNAMIN - elem2
to define
IF Z<-.6 IF Z-1
I
constants
FNAMAX - eleml FNAMAX - elem2
DEF FNAMIN(eleml,elem2) function to find minimum of IF eleml
two
standard atmosphere height-gain:
THEN Z>.6 THEN THEN
FNU - 8.686*LOG(Z) FNU - 15.88*LOG(Z/.6)^I.4 FNU - 19.85*(Z^.47-.9)
-
U(z)
4.3
END DEF
B I I I I I I I
I I I SUB FFACTR(freq, ht, hr, sbdht, humid, rk, hi
-
ht
h2 -
hr
polar$, antyp$, bwidth, elevat, rnsubs, wind, r, FF) static
IF hl > h2 THEN swap hl,h2
'swap
delta,_
antenna heights
3
initialize optical call opconst
3
initialize diffraction/troposcatter region constants call dconst wvloss = wv.atten * r ' water vapor absorbtion
region constants
Initialize antenna call antpar
parameters
Calculate range to skipzone if surface-based IF sbdht > 0 THEN call skipzone Calculate fsloss
free-space fsterm
=
r
>-
rsubd
+ 8.686
' '
approximate rl at 1% max range in optical
THEN
dfloss = sbdloss IF dfloss < diff
fsloss THEN diff
-
dfloss
END IF ff - diff ELSE r
>
opmaxd
THEN
call difint(opmaxd, ELSE IF r <- opmaxd THEN END IF END IF
3
I
I
ff -
END
SUB
-(ff
+
wvloss)
present
* LOG(r)
call dloss(r, DIFF) IF sbdht > 0.0 THEN call sbd(r, SBDLOSS)
IF
duct
loss value
rlmin 0.01*r*hl / (hl+h2) call oplimit(OPMAXD, OPMAXL) IF
loss
opmaxl, call
r,
FF)
opticf(r,
FF)
of range region
SUB antpar staticI Process: Initialize antenna parameters Inputs from common block: antyp$, bwidth, elevat outputs to common block: antbwr,antelrantfac,elmaxr,patrfac
Subroutines called: Subroutine
NoneI
called by:
FFACTR
antbwr - 1.745e-2 * bwidth antelr - 1.745e-2 * elevat elmaxr - 1.047 IF antypS <> "OMNI" THEN IF antyp$ - "GAUSS" THEN A antfac LOC(2.O)/(2.O * SIN(antbwr/22.0)O patrfac amax - SQR(IO.11779 * SIN(antbwr/2.OY^2.O) =SIN(antelr)
ESelmaxr
- antelr + ATN(amax /
SQR(l.O
-
amax^2))U
IF antyp$ - "CSC-SQ" THEN elmaxr - antelr + 0.78525 antfac - SIN(antbwr)I ELSE IF (antypS "SINX/X") or (antyp$ - "IHT-FINDER") THEN antfac / SIN(antbwr/2.O) amax - FI/antfacI patrfac - -ATN(amax /SQR(l.0 - amax^2)) IF antyp$ - "SINX/X"1 THEN elmaxr - antelr-patrfac END IF =1.39157
END IF END IF
END IF
END SUB
B 8
i
I I SUB antpat(angle,
3
PATFAC)
static
Calculate the pattern factor Inputs from common block: alpha, antbwr, antelr, antyp$, patrfac Inputs from argument list: angle Outputs to common block: None Outputs to argument list: patfac Subroutines called: None Subroutine called by: opffac
'Process:
patfac -
antfac
1.0
IF antyp$ <> "OMNI" THEN IF antyp$ - "HT-FINDER" AND angle > antelr THEN alphaO - alpha ELSE 'SINX/X or CSC-SQ or GAUSS alphaO - antelr END IF apat - angle - alphaO
I
3 I
IF antyp$ - "CSC-SQ" THEN patfac - FNAMIN(1.0, FNAMAX(O.03, 1.0 + apat/antbwr)) IF apat>antbwr THEN patfac - SIN(antbwr)/SIN(ABS(apat)) ELSEIF antyp$ - "GAUSS" THEN patfac - EXP(antfac * (SIN(angle) IF patfac < 0.03 THEN patfac - 0.03
ELSE
patrfac)^2.0)
'SIN(X)/X
IF apat<>O.O THEN IF angle <- alphaO + patrfac THEN patfac - 0.03 ELSE ufac - antfac * SIN(apat) patfac - FNAMIN(1.0, FNAMAX(O.03, END IF END IF END IF END IF END SUB
I I I
3
SIN(ufac)/ufac))
1 I I SUB dconst static Initialize variables
Process:
for the
troposcatter region Inputs from common block: ae, delta, rk,
diffraction
n
and
freq, fsterm, hl,
h2
rnsubs
Outputs
to common block: atten, cl, c2, c3, c4, c5, c6, c7 del, difac, dtot, fterm, f3, hl4pil, h24pil, hlm hmin, horizn, rnsterm, rns2, rsubd, tfac, tsubl tsub2, zfac Subroutines called: hgain Subroutine called by: FFACTR tsubl - SQR(hl * ae/500.O) / aei tsub2 - SQR(h2 * ae/500.0) / ae hl4pil - hl * O.0419*freq a h24pil - h2 * 0.0419*freq rnsterm - 0.031 0.00232 * rnsubs + 5.67E-6 horizn - 3.572 * (SQR(rk*hl) + SQR(rk*h2)) tfac - 0.08984 / rk f3 - freq^3 rns2 - 0.2 * rnsubs
*
$
I
rnsubs^2
I
Diffraction region constants qrfreq -
freq^(1.0/3.0)
fterm - qrfreq / 190.0 fqterm - qrfreq^2 / 2129.94 uht - FNU(fqterm*hl) uhr - FNU(fqterm*h2) dtot - fsterm - uht
rkmin IF
-
-
uhr
i
rk
rkmin <
1.3333 THEN rkmin - 1.3333
horiznmin - 3.572 * (sqr(r1.c-in*hl)+sqr(rkmin*h2)) rsubd - horiznmin + 230.2 * (rkmin^2 / freq)^(l.0/3.0) IF delta - 0 THEN del - 0
1
no evaporation duct height
3
ELSE
Following terms for NOSC evaporation duct model rfac
- 0.04705 * qrfreq
zfac - 0.002214 * qrfreq^2
hmin - 1.0 zl - hl IF hmin z2 - h2 IF hmin
* zfac > zl THEN zl - hmin * zfac > z2 THEN z2 - hmin
del - delta * zfac IF del > 23.3 THEN del IF del >- 10.25 THEN
-
23.3
BIO
i m
Duct height greater than 10.25 meters ci - -0.1189 *dl+559 c3 - 1. 3291*SIN(0. 2l8*(del-l0.0)"0. 77)+0.2171*LOG(del) c4 - 87.0 - SQR(313.29 - (del hlowmax - 4.0 * exp(-0.31*(del + 6.0 him - hlowmax/4.72 arg - c3 * "lm1.5 slope = c3 *ci * 1.5 * SQR(hlm) / TAN(arg) c7 - 49.4 *exp(-0.1699*(del 10.0)) + 30.0 frnax = ci LOG(SIN(arg)) + c4 - c7 -25.3)^2)
I Uc6 3 Ic4 3 I
-10.0))
him
=
c5 - fmax
ELSE
*slope
/ fmax
/hlm~c6
Duct height less than 10.25 meters c2 = SQR(40623.61 - (del + 4.4961 )A2) 201.0128 cl = (-2.2 * exp(-0.244*del) + 17.0) * 4.72 ^(-C2) = SQR(14301.2 - (del + 5.32545)^2) - 119.569 c3 - (-33.9 * exp(-0.5l7000l*del) - 3.0) * 4.72 ^(-C4) c5 = 41.0 * exp(-0.41*del) + 61.0 END IF determine the height-gain function for the evaporation duct. Note! The variable "DUMMY" contains the heightgain function for a surface-based duct which is not used in this subroutine. call hgain(hl, DUMMY, FZT)
call ngain(h2, DUMMY,
FZR)
Note. The # symbol is QuickBASIC double precision notation atten - 92.516 - SQR(8608.7593# - (del - 20.2663)^2) IF atten < 0.0009 THEN atten = 0.0009
atten - atten * rfac IF del IF del difac END IF END SUB
3.8 THEN tlm = 3.8 THEN tim = 51.1 + tim - fzt
<= >
216.7 222.6 fzr
Bl11
+ +
del * 1.5526 (del - 3.8) * 1.1771 4.343*LOG(rfac)
U I I SUB
difint(opmaxd, opmaxl, Process:
"
r,
FF)
static
Calculates 20 times the natural logarithm for the propagation factor within the intermediate region, i.e. for ranges greater than opmaxd and less than
rsubd.
*
Inputs from common block: fsloss, rsubd, sbdh Inputs from argument list: diff, opmaxd, opmaxl, Outputs to common block: None Outputs to argument list: ff, r, rsubd Subroutines called: dloss, sbd Subroutine called by: FFACTR call dloss(rsubd, DIFF) deltaf - (r - opmaxd) * (opmaxl
ff
I
-
opmaxl
+
- diff) /
r,
sbdloss
3
(opmaxd-rsubd)
deltaf
IF sbdht > 0.0 THEN dloss - ff + fsloss call sbd(r, SBDLOSS) IF sbdloss < dloss THEN dloss ff - dloss - fsloss
sbdloss
END IF END SUB
3
U U I I I BI2
I
I
I DIFF)
SUB dloss(r,
3
static
Calculate the diffraction region loss atten, delta, difac, from common block: fterm r, tloss Inputs from argument list: None Outputs to common block: diff, r Outputs to argument list: tropo Subroutines called: FFACTR, difint Subroutine called by:
'Process:
dtot,
Inputs
diffraction region
Calculate x
-
*
fterm
loss using Kerr's
model
r
tlvx - 10.99 + 4.343 * LOG(x) diff - dtot + 8.686 * LOG(r)
-
17.55 * x tlvx
IF delta <> 0.0 THEN -
diffe
difac
Use diff
END
ENT IF
lesser -
+
4.343
*
LOG(r)
+
atten
*
r
diff THEN
IF diffe <
of
Kerr and NOSC models
diffe
IF
diff - diff + exloss call tropo(r, T!.OSS) Add the dif
-
troposcatter loss
diff
-
to
the diffraction
loss
tloss
IF dif >- 18.0 THEN diff - tloss ELSEIF dif diff
-
>diff
-18.0 THEN - 4.343
*
LOG(1
+
EXP(dif/4.343))
END IF Return 20*LOG(F) at range = r in diffraction diff - diff - fsterm - 8.686*LOG(r) END SUB
I I I I IBI
region
fsterm
I I I SUB gtheta(p$,
rl,
R,
THETA, R2)
static
Process:
Calculates optical phase-lag difference angle, theta, from reflection point range, rl. Inputs from common block: ae2, aeth, hl, h2, h24ae2, rl
i
the fac p$, rl, phi Inputs from argument list: psi Outputs to common block: Outputs to argument list: p$, psi Subroutines called: ref Subroutine called by: oplimit, rliter hip - hl - rl 2 / ae2 rkpsi - hip / rl psi = 0.001 * rkpsi r2 = (sqr(rkpsi^2 + h24ae2) r rl + r2 h2p - h2 - r2^2 / ae2 call ref(p$, psi, PHI) theta - phi + thefac * hip * END SUB
rkpsi)
h2p
/
*
aeth
r
I I I i I I
I BI4
I
I I SUB hgain (h, FZBD1, FZBD2) STATIC
3 3
3
Process:
Calculates height-gain factor in dB for a specified height Inputs from common block: cl, c2, c3, c4, c5, c6, c7, del 'freq, h, him, hmin, sbdht, zfac Inputs from argument list: h Outputs to common block: None Outputs to argument list: fzbdl, fzbd2 Subroutines called: None Subroutine called by: dconst, skipzone '
fzbdl -
0
-
0
fzbd2
Surface-based duct height-gain factor IF (sbdht > 0) THEN z1 - h / sbdht IF ((Freq <- 150!) AND (zl < .8)) THEN_ f:bdl - -60! * (zl - .5) 2 IF
IF IF
((Freq <= 150!) AND fzbdl 1.14 * zl
((Freq > 150!)
fzbdl
((Freq fzbdl
END IF
-
10!
> -
-
AND
200
150!) 7.5
*
*
AND zl
^
(zl >= .8)) THEN_ (-6.26) 10!
(zl < (zl - 1.0)) .5) ^ THEN_ 4 (Freq <= 350!) AND (-13.3)
(zl
>-
l!))
10!
-
IF ((Freq > 350!) fzbdl - 12.5 *
AND (zl >= zl ^ (-8!)
l!)) THEN_ 15!
-
Evaporation duct height-gain factor IF (del > 0) THEN z2 IF
- h * zfac z2 < hmin THEN
z2
-
IF
(Del
IF
z2
>=
(z2
fzbd2 ELSE
z2
- hmin
/ 4.72 10.25)
> him) =
C5
*
THEN
THEN (z2
^
C6)
+
C7
fzbd2 - CI * T.OG(SIN(C3 * (z2 END IF ELSE fzbd2 END IF END IF END SUB
I IB5
(CI
* z2
^ C2)
+
(C3
* z2
1.5)))
*
C4)
+ C4
4- C5
.AEN_
U I SUB
opconst
3
static
Process: Initializes constants for optical region Inputs from common block: antype$, freq, hi, h2, hr, ht humid, polar$, rk, wind Outputs to common block: ae, ae2, aeth, fsterm, h24ae2, hbar hbfreq, hdif, horiznl, rilim, rn2.imag, rn2.real thefac, wv.atten Subroutines called: None Subroutine called by: FFACTR
Variables for REF subroutine IF polar$ <> "H" THEN IF freq <- 1500 THEN eps - 80 'salt water sigma = 4.3 'salt water ELSEIF freq <= 3000 THEN eps - 80 - 0.00733 * (freq - 1500) sigma = 4.3 + 0.00148 * (freq 1500) ELSEIF freq <= 10000 THEN eps = 69 - 0.00243 * (freq - 3000) sigma ELSE eps = sigma END IF
=
6.52
+
0.001314
*
(freq
of
square
of
-
for miscellaneous 6371
/ /
((freqg-183.3i^2 ((freqg-323.8 V2
water vapor attenuation wv.atten - (0.067 + wvl
of
refraction
'rms wave height '(hbar*2*Pi)/wavelength
subroutines ' effective
2.0 * ae rk * 6.371 aeth * 2.0 - h2 * 4.0/ae2 = freq * 4.193E-5
9.0 4.3
index
sigma/freq
hdif - (hr - ht) * 1.OE-3 fsterm - 32.45 + 8.686 * LOC(freq) freqg - freq / 1000.0 wvl - 3.0 / ((freqg- 22.3)^2 + 7.3) wv2 wv3
3000)
i
Variables for RUFF subroutine hbar - 0.0051 * (0.51477*wind)^2 hbfreq - 0.02094 * freq * hbar
twoae = aeth = ae2 = h24ae2 thefac
I
51.99 = 15.718
real & imaginary part rn2.real = eps rn2.imag - (-18000) * END IF
Variables ae - rk *
-
permittivity conductivity
+ +
rate in + wv2 +
BI6 1
earth
radius
-
km
'
4*Pi
'
free space loss term frequency in Gliz
/
wavelength
I
6.0) 10.) dB/km wv3) *
freqg^2
*
humid/l10O))O.E
3
I
I I Variable for RIITER subroutine horiznl - 3.572 * (SQR(rk*hl)) Variables for OPLIMIT subroutine Note: rllim - rl at psilim psilim - 0.01957 / (rk*freq)^(l./3.) ' grazing angle limit rkpsi - 1000 * psilim rllim - (SQR(rkpsi*rkpsi + hl*4/ae2) rkpsi)*aeth END SUB
SUB i
opffac(gamma,
range,
psi,
rl,
r2,
PATD,
DR)
static
Calculates parameters used to determine the pattern propagation factor, F, in the optical region. Calculate antenna pattern factor for direct ray, alpha, and reflected ray, beta. Inputs from common block: ae, hdif, patfac, patrfac, psi rmag, twoae gamma, patfac, range, rl, r2, ruf Inputs from argument list: Outputs to common block: alpha Outputs to argument list: alpha, beta, sinpsi, patd, dr Subroutines called: antpat, ruf Subroutine called by: oplimit, opticf
'Process:
I
3
patfac - 1 alpha - (hdif/range) - (range/twoae) sinpsi - SIN(psi) CALL antpat(alpha, PATFAC) patd - patfac beta - -(gamma + psi) CALL antpat(beta, PATFAC) Calculate surface roughness coefficient call ruff(sinpsi, RUF) divfac - I / (sqr(l.0 + (2.0*rl*r2/ae) / dr - patfac * ruf * divfac * rmag
END SUB
I I I i
BI 7
(range*sinpsi)))
I I SUB opticf(r,
FF)
static
Process:
Calculates the optical path-length difference angle, theta, by solving a cubic equation for the reflection point range, rl. from common block: ae, aeth, ae2, hl, h2, ht, hr
Inputs
polar$,
thefac
Inputs from argument list: dr, patd, phi, r Outputs to common block: psi Outputs to argument list: ff, gamma, polar$, psi, Subroutines called: opffac, ref Subrouciiie called by: FFACTR (hi / (hl + h2)) -. 5* r v = .5 * r * r - aeth w aeth * r * hl epsr - 0.050 rl t
r,
r2
i
* r
-
rl,
I I
-
dd jk -
2 . 1
*
rl
rl^3
=
fprl dd -
+ h2)
epsr
WHILE jk < 10 AND jk jk + 1 frl
* (hl
+
(3.0 * frl/fprl
-
rl
-
U
abs(dd) > epsr
(t
*
+
(v
*
1- (2.0 *
t
rl^2)
rlA2)
rl) + * rl)
w
+ v
dd
IF rl < 0.0 OR rl > r THEN WEND r2 - r - rl htp= hl - rl*rl/ae2 hrp - h2 - r2*r2/ae2 psi l.e-3 * htp / rl call ref(polar$, psi, PHI) theta - (thefac * htp * hrp / IF ht >- hr THEN gamma - r2/ae
rl
-
r)
+ phi
r/2.0
i
ELSE
gamma - rl/ae END IF call opffac(gamma, r, psi, rl, r2, PATD, DR) fsqrd - patd^2 + dr^2 + (2.0 * dr *patd * COS(theta)) IF fsqrd < l.e-7 THEN fsqrd - l.e-7 ff - -4.343 * LOG(fsqrd) END SUB
I U BI8
I
SUB oplimit(OPMAXD, OPMAXL) static Process:
3
Calculates the maximum range, opmaxd, in the optical region and the loss at opmaxd. Inputs from common block: ae, ae2, del, hr, ht, pi, polar$ rllim, rlmin Inputs from argument list: dr, paLd, r, rl, r2, theta the tal im Outputs to common block: exloss, rilim, rimin Outputs to argument list: gamma, opmayd, opmaxl, polar$, r, rl r2, thetalim
Subroutine called by: Initial guess for rI angle limit, rllim).
5 I I 3 I 3
rl - rllim theta value at
rt'heta
-
FFACTR (for wavelength/4 limit based on grazing
1/4 wavelength limit, horizontal polarization
1.5 * Pi
call rliter("H", rtheta, Rl, R2, R) IF rllim > rl THEN rl = rllim 'grazing angle
rllim
-
IF rllim
limit applies
rl <
rlmin THEN
rlmin
=
0.5
*
rllim
IF del > 0 THEN call gtheta(polar$, rllim, R, THETALIM, R2) thetalpk - 2.0 * Pi call gtheta(polar$, rlmin, R, THETA, R2) IF thetalpk > theta THEN thetalpk -theta
IF del < 10.25 THEN thetalim = thetalim + del/lO.25 *(thetalpk ELSE thetalim - thetalpk END IF call rliter(polar$, thetalim, R1LIM, R2, R)
END IF
rl - rllim call gtheta(polar$, IF ht >- hr THEN
gamma
-
r2/ae
ELSE gamma
-
rl/ae
rI,
R, THETA,
END IF
B 19
R2)
-thetalim)
U I call opffac(amma,
r, psi,
rl,
r2,
PATD, DR)
fsqrd - patd 2 + dr^2 + (2,0 * dr* patd * COS(theta)) IF fsqrd < l.e-7 THEN fsqrd - l.e-7 opmaxd - r opmaxl - -4.343 * LOG(fsqrd) ' -20 * LOGIO(F) exloss - -8.686 * LOG(patd) END
U
SUB
I SUB
rliter(p$,
rtheta,
Rl,
R2,
R)
static
Process:
Finds reflection point range "rl" corresponding an angle "rtheta" Inputs from common block: horiznl Inputs from argument list: f, fl, p$, r, rl, r2, rtheta Outputs to common block: None Outputs to argument list: p$, r, rl, r2, Subroutines called: gtheta Subroutine called by: oplimit irlmda dd
-
to
U 3
0
rl
WHILE abs(dd) > 0.001 AND irlmda < 100 call gtheta(p$, rl, R, F, R2) call gtheta(p$, rl+0.001, R, Fl, R2) fp - (fl - f) /f0.001 dd - (rtheta f) / fp irlmda
IF
-
irlmda
+
I
dd > -rl THEN IF dd + rl <- horiznl THEN rl - rl+dd ELSE
rl - (rl+horiznl)/2.0 END IF ELSE rl - rl/2.0 END IF WEND END SUB
I I B20
3
SUB ref(p$, psi,
PHI)
static
Process:
3
Calculates magnitude, rmag, and phase lag, the reflection coefficient from common block: pi, rn2.imag, rn2.real
Inputs
Inputs from argument list:
p$, psi
Outputs to common block: rmag Outputs to argument list: phi Subroutines called: None Subroutine called by: gtheta, opticf rmag
IIF
phi
-1.0 -PI
-H" THEN
p$ <>
sinpsi - SIN(psi) y - rn2.imag x - rn2.real - COS(psi) ,2 rmagroot - (x^2 + y^2)^0.25 angroot -ATN(y/x) / 2.0 root.real - rmagroot * COS(angroot) root.imag - rmagroot * SIN(angroot) rn2.real * sinpsi - root.real ct - rn2.real * sinpsi + rootreal bt - rn2.imag * sinpsi - root.imag
Iat £dt
rn2.imag *
-
sinpsi + root.imag
refv.real - (at*ct + bt*dt) /(ct'2 refv.imag - (bt*ct - at*dt) /(ct^2 rcv - sqr(refv.rea 1A 2 + refv.imag^2) IF refv.real <> 0.0 THEN
dt'2) d t2)
+ +
phiv =ATN(refv.imag/refv.real) pi IF efv.imag < 0.0 THEN phiv - phi IFrefv.imag < 0.0 THEN
phiv
1 I I
=
-
-
-
0.0
THEN phiv
- phiv
+
2.0*PI
phiv
IF p$ - "C" THEN rx - SQR(l.0 + rcv^2 + (2.0 * rcv rmag - rx / 2.0 a-rcv * SIN(phiv + PI) / rx a-ATN(a / SQR(1 - a^*2)) phi phi
2.
phiv
IF phiv -0.0 rmag - rcv
phi
phiv
. +2.0
-
PI
-
-phi
a
1F phi < 0.0 THEN phi
-
phi + 2*P1
END IF END IF
END SUB
B21
*
COS(PI
-phiv)))
phi,
of
I i I SUB
ruff(sinpsi, RUF)
static
Process:
Calculates the surface-roughness coefficient function of psi Inputs from common block: hbar, hbfreq, psi Inputs from argument list: sinpsi Outputs to common block: Nonne Outputs to argument list: ruf Subroutines called: None Subroutine called by: opffac ruf -
*
.159155
hfpsi ruf -
ELSEIF ruf
ELSE ruf
END
n
1.0
IF hbar <> 0.0 THEN hfpsi - hbfreq * psi IF
as a
<- 0.11 THEN EXP((-2) * (hbfreq*sinpsi)^2) hfpsi <= 0.26 THEN = 0.5018913 - SQR(0.2090248 (hfpsi-0.55189)^2) =
IF
SUB
SUB
sbd(r,
U SBDLOSS)
static
Process: Calculate surface-based duct loss Inputs from common block: exloss, fofz, rsbd, Inputs from argument list: r Outputs to common block: None Outputs to argument list: sbdloss Subroutines called: None Subroutine
called by:
difint,
IF
END IF END SUB
B22i
rsbdloss,
sbdht
FFACTR
IF sbdht - 0.0 THEN sbdloss = 1000.0 ELSE IF r < rsbd THEN sbdloss - rsbdloss + (rsbd - r) ELSE sbdloss - fsterm + 8.686*log(r)
END
i
I
0.15
END IF
END
i
+ exloss -
fofz
+ exloss
I I
I I U SUB
skipzone
static
irocess:
Calulates skip-zone range if a surface-based duct is present and calculates the ratge to the start of the diffraction region. Inputs from common block: ae, fsterm, rlmin, sbdht Inputs from argument list: fofz Outputs to common block: rsbd, rsbdloss, rsubd Outputs to argument list: h2 Subroutines called: hgain Subroutine called by: FFACTR = 0 IF hl < och AND h2
rsbd
dmdh
0.001
< och
/ ae
alphaO
* dmdh * och * dmdh / - sqr(delm2)
rayO
alphaO
elm2
gtrap -
alphat rayl = alphar ray2 -
och
i
2.0
(O.l*sbdht)
/ gtrap
= sqr(delm2 (och-hl) * 2.0 * dmdh) rayO + (alphaO - alphat)/dmdh sqr(delm2 (och-h2) * 2.0 * dmdh) rayO + (alphaO alphar) / dmdh
rsbd - (rayl + ray2) IF rsbd < rlmin THEN i
THEN
/ 1000 'SBD rsbd - rlmin
'
start
range,
km
determine the height-gain function for surface-based duct. Note! The variable "DUMMY" contains the heightgain function for an evaporation duct which is not used in this subroutine. call hgain(h2, FOFZ, DUMMY) rsbdloss - fsterm + 8.686*log(rsbd) - fofz END IF END SUB
I
I I I I i
B2 3
i I I static
TLOSS)
tropo(r,
SUB
I
Calculate the troposcatter loss based upon Yeh with frequency-gain factor, hO, from NBS 101 Inputs from common block: ae, exloss, f3, hi, hl4pil, h2 h24pil, horizn, rns2, rnsterm, tfac, tsubl, tsub2 r Inputs from argument list: Outputs to argument list: tloss Process:
Subroutines called: None Subroutine called by: dloss tsubO ttot zeta
=
r / ae tsub0 -
tsubl
ttot/2.0
-
+
tsub2
-
tsubl
+
(hi
+ tsub2 + (h2 hl) * ttot * ttot THEN rsubl = 0.1
IF
THEN
s
rsub2 =
<
0.1
zeta /
chi
rsub2
=
/
h2)
chi ttot/2.0 rsubl = hl4pil rsub2 = h24pil IF rsubl < 0.1
/
(l000.0*r) (1000.0*r)
I
0.1
I
IF s > 10.0 THEN s IF s < 0.1
THEN
110.0 s - 0.1
q - rsub2 / (s*rsubl) IF q > 10.0 THEN q - 10.0
THEN q - 0.I
IF q < 0.1 hsubO
=
(s
*
r
*
ttot)
etas - 0.5696*hsubO IF etas > 5.0 THEN IF etas < 0.01 THEN csubl csub2
= =
/
(I
+
s)^2
* (I + rnsterm * etas = 5.0 etas
=
EXP(-3.8e-6
hsubO^6))
*
0.01
16.3 + 13.3 * etas 0.4 + 0.16 * etas
hOrl
- csubl
*
(rsubl
+ csub2)^-1.333
hOr2
-
*
(rsub2
+
csubl
I i
csub2)^-1.333
hO = (hOrl + hOr2) / 2.0 delhO - 1.13 * (0.6 0.434*LOG(etas)) * LOG(s) * LOG(q) IF delhO > hO THEN hO = 2.0 * hO ELSE hO - hO + delhO IF hO tloss
tloss END SUB
< -
0.0
THEN
hO
=
0.0
1l4.9+tfac*(r-horizn) + - tloss + exloss
4.343*LOG(r^2*f3)
-
rns2
+
hO
I
I I B24i
Public reporting burden tV this collection of information is estimated to average 1 hour Per response. Including thetime for revleviing InstructIons. searching existing data sources. gathering arid maitaning the data needed, and completing and reviewing the collection of Intomatlon Send comments regarding this burden eatimate of any other aspect of this collection of information .nclodlflg AilIngton VA 22202-4302 sUggestlons forreducing M15burden, toWashington Headquarters Servces, D1rectorate for InforrruIon Operations and Reports. I2t15Jefferson Davis Highway, Suite 12134. and to the Office of Management and Bud"e. Paperwork Reduction Project (0704-0188). Washington. DC 20603.__________________ 3. REPORTTYPE AND DATESCOVERED
2 REPORT DATE
1 AGENCY USEONLY (Leave b"V
IFebruary
Intermin
1990
5 FUNOING NUMBERS
4 TITLEAND SUBTITLE
PE: 0602435N
ENGINEER'S REFRACTIVE EFFECTS PREDICTION SYSTEM (EREPS)
a
DN888 715
AUTOR(SWU:
W. L. Patterson
H. V. Hitney
A. E. Barios
C, P. Hattan
R. A. Paulus
G. E. Lindem________________
7 PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
K D. Anderson S. PERFC ,MING ORGANIZATION
NOSC TD 1342 Rev. 2.0
Naval Ocean Systems Center San Diego, CA 92152-5000 aSPONSORINOI1MONITORINO AGENCY NAME(S) Office of Naval Technology Arlington, VA 22217
I11t
AND ADDRESS(ES)
tO SPONSORING/MONITORING
SUPPLEMENTARY NOTES
12b DISTRIBUTION CODE
12a. DISTRiBUTtON/AVAJL-ABLfTY STATEMENT
Approved for public release; distribution is unlimited.
200 wonf) 13 ABSTRACT(Ataaxnrun
TIhe pu-pose of this document is to introduce the contents and operation of the Engineer's Refintive"Effects Prediction System (EREPS), Revision 2.0. EREPS is a system of indlividual stand-alone IBM/ PC-compatible programs that have been designed to assist an engineer in properly assessing elect rornagnetic (EM) propagation effects of the lower atmosphere on proposed radar, electronic warfare, or communication systems. The EREPS models account for effects from optical interference, diffraction, tropospheric scatter, refraction, evaporation and surface-based ducting, and water-vapor absorption under horizontally homogeneous atmospheric conditions.
IEREPS IOF
15 NUMBER CWPACGL S
4 SUBJECT TERMS
203 16PRICECODE
electromagnetic (EM) propagation effects
17 SECURITYCL~ASSIFICATION
REPORT
UNCLASSIFIED NSN 7540dt-M5066
18t SECURITY CLAS-IFICATION
OFTHISPAGE
UNCLASSIFIED
1it SECURITY CLASSIFICATION
20 UIMITATION OF A&S;RACT
OF ABSTRACT
UNCLASSIFIED
SAME AS REPORT Slanrtjld form 2it8