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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




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


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.




a


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



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

__

-4j

"

20

PRPGTO3ATRd A5

IIJ

39 6 6

1.5

Hz rpm am

1999 15 I .9

PD PRPA, 2

8

285 1.3

]BI deg PRF SCAN RT

2-RCS

3989 NOR 25 25

RADR HT n kn RANCE SINX/X ANT TYPE 3 VER M deg PK POU P MID"H

E 1600 C H T

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

285

us

CHdi

,

25

W

iN

40-

I

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

""I-

.

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-

-25 HIN AC nrad 10 AflX AND nrad V REFLECTED RAYS PROFILE CHARACTER IST ICS

flected a

8000-

H E 1

608-

500 50

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

H

Elevated Duct at 58880

1

i

608

G :*

H

i

TRAM HT: 5080 n

~288808

I

~

~

~~

384858

~

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 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 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 apatO.O THEN IF angle 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
- 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 -

-

AND

200

150!) 7.5

*

*

AND zl

^

(zl >= .8)) THEN_ (-6.26) 10!

(zl < (zl - 1.0)) .5) ^ THEN_ 4 (Freq -

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 rl THEN rl = rllim 'grazing angle

rllim

-

IF rllim

limit applies

rl
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
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(EREPS). - Defense Technical Information Center

NavaTechnical Document 1342 Revislon 2.0 (0 Fobruary 1900 Engineer's Refractive Effects Prediction System (EREPS) Revision 2.0 , W, L, Patterson...

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