QGIS User Guide Release 2.8 QGIS Project - QGIS Documentation [PDF]

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QGIS User Guide Release 2.8

QGIS Project

July 30, 2016

Contents

1

Preâmbulo

3

2

Convenções 2.1 Convenções GUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Convenções de Texto ou Teclado . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Instruções específicas da plataforma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 5 5 6

3

Prefácio

7

4

Características 4.1 Visualização de dados . . . . . . . . . . . . . 4.2 Exploração de dados e compositores de mapas 4.3 Criar, editar, gerir e exportar dados . . . . . . 4.4 Analyse ; imagerelpath="images/test_image.jpg"; projectpath=qgis.core.QgsProject.instance().fileName(); import os.path; path=os.path.dirname(str(projectpath)) if projectpath != ’’ else None; image=os.path.join(path, imagerelpath); import subprocess; subprocess.Popen( [command, image ] );

Another Python action example is the one that allows us to add new layers to the project. For instance, the following examples will add to the project respectively a vector and a raster. The names of the files to be added to the project and the names to be given to the layers are , group=’Custom’) def myfunc(value1, value2 feature, parent): pass

The short example creates a function ‘myfunc’ that will give you a function with two values. When using the args=’auto’ function argument the number of function arguments required will be calculated by the number of arguments the function has been defined with in Python (minus 2 - feature, and parent). This function then can be used with the following expression: myfunc(’test1’, ’test2’)

Your function will be implemented in the ‘Custom’ Functions of the Expression tab after using the Run Script button.

Further information about creating Python code can be found on http://www.qgis.org/html/en/docs/pyqgis_developer_cookbook/inde The function editor is not only limited to working with the field calculator, it can be found whenever you work with expressions. See also Expressions. .

136

Chapter 12. Trabalhando com Informação Vectorial

CHAPTER 13

Trabalhando com Informação Matricial

.

13.1 A trabalhar com Dados Matriciais This section describes how to visualize and set raster layer properties. QGIS uses the GDAL library to read and write raster , ATTRS{idProduct}=="0003", MODE="666"

Depois disto é necessário ter a certeza que o módulo kernel do garmin_gps não está carregado rmmod garmin_gps

e de seguida pode usar as Ferramentas GPS. Infelizmente, parece existir um bug #7182 e normalmente o QGIS pára várias vezes antes da operação trabalhar bem. BTGP-38KM encoding="UTF-8"?>

The parser reads this definition and creates a new tab inside the Toolbox when you select the module. A more detailed description for adding new modules, changing a module’s group, etc., can be found on the QGIS wiki at http://hub.qgis.org/projects/quantum-gis/wiki/Adding_New_Tools_to_the_GRASS_Toolbox. .

16.9. The GRASS Toolbox

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Chapter 16. Integração GRASS SIG

CHAPTER 17

Infraestrutura do Processamento QGIS

.

17.1 Introdução This chapter introduces the QGIS processing framework, a geoprocessing environment that can be used to call native and third-party algorithms from QGIS, making your spatial analysis tasks more productive and easy to accomplish. In the following sections, we will review how to use the graphical elements of this framework and make the most out of each one of them. There are four basic elements in the framework GUI, which are used to run algorithms for different purposes. Choosing one tool or another will depend on the kind of analysis that is to be performed and the particular characteristics of each user and project. All of them (except for the batch processing interface, which is called from the toolbox, as we will see) can be accessed from the Processing menu item. (You will see more than four entries. The remaining ones are not used to execute algorithms and will be explained later in this chapter.) • A caixa de ferramentas. O elemento principal do GUI, é usado para executar um algoritmo único ou correr um processo batch baseado nesse algoritmo.

Figure 17.1: Processing Toolbox

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• The graphical modeler. Several algorithms can be combined graphically using the modeler to define a workflow, creating a single process that involves several subprocesses.

Figure 17.2: Processing Modeler • The history manager. All actions performed using any of the aforementioned elements are stored in a history file and can be later easily reproduced using the history manager. • A interface de processamento batch. Esta interface permite que possa executar processos batch e automaticamente a execução de um único algoritmo num múltiplo conjunto de dados. In the following sections, we will review each one of these elements in detail. .

17.2 A caixa de ferramentas The Toolbox is the main element of the processing GUI, and the one that you are more likely to use in your daily work. It shows the list of all available algorithms grouped in different blocks, and it is the access point to run them, whether as a single process or as a batch process involving several executions of the same algorithm on different sets of inputs. The toolbox contains all the available algorithms, divided into predefined groups. All these groups are found under a single tree entry named Geoalgorithms. Additionally, two more entries are found, namely Models and Scripts. These include user-created algorithms, and they allow you to define your own workflows and processing tasks. We will devote a full section to them a bit later. In the upper part of the toolbox, you will find a text box. To reduce the number of algorithms shown in the toolbox and make it easier to find the one you need, you can enter any word or phrase on the text box. Notice that, as you type, the number of algorithms in the toolbox is reduced to just those that contain the text you have entered in their names. In the lower part, you will find a box that allows you to switch between the simplified algorithm list (the one explained above) and the advanced list. If you change to the advanced mode, the toolbox will look like this: 194

Chapter 17. Infraestrutura do Processamento QGIS

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Figure 17.3: Processing History

Figure 17.4: Batch Processing interface

17.2. A caixa de ferramentas

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Figure 17.5: Processing Toolbox

Figure 17.6: Processing Toolbox (advanced mode)

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In the advanced view, each group represents a so-called ‘algorithm provider’, which is a set of algorithms coming from the same source, for instance, from a third-party application with geoprocessing capabilities. Some of these groups represent algorithms from third-party applications like SAGA, GRASS or R, while others contain algorithms directly coded as part of the processing plugin, not relying on any additional software. This view is recommended to those users who have a certain knowledge of the applications that are backing the algorithms, since they will be shown with their original names and groups. Also, some additional algorithms are available only in the advanced view, such as LiDAR tools and scripts based on the R statistical computing software, among others. Independent QGIS plugins that add new algorithms to the toolbox will only be shown in the advanced view. In particular, the simplified view contains algorithms from the following providers: • GRASS • SAGA • OTB • Native QGIS algorithms In the case of running QGIS under Windows, these algorithms are fully-functional in a fresh installation of QGIS, and they can be run without requiring any additional installation. Also, running them requires no prior knowledge of the external applications they use, making them more accesible for first-time users. If you want to use an algorithm not provided by any of the above providers, switch to the advanced mode by selecting the corresponding option at the bottom of the toolbox. Para executar um algoritmo, faça duplo clique no seu nome na caixa de ferramentas.

17.2.1 O diálogo do algoritmo Once you double-click on the name of the algorithm that you want to execute, a dialog similar to that in the figure below is shown (in this case, the dialog corresponds to the SAGA ‘Convergence index’ algorithm).

Figure 17.7: Parameters Dialog This dialog is used to set the input values that the algorithm needs to be executed. It shows a table where input values and configuration parameters are to be set. It of course has a different content, depending on the require17.2. A caixa de ferramentas

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ments of the algorithm to be executed, and is created automatically based on those requirements. On the left side, the name of the parameter is shown. On the right side, the value of the parameter can be set. Although the number and type of parameters depend on the characteristics of the algorithm, the structure is similar for all of them. The parameters found in the table can be of one of the following types. • A raster layer, to select from a list of all such layers available (currently opened) in QGIS. The selector contains as well a button on its right-hand side, to let you select filenames that represent layers currently not loaded in QGIS. • A vector layer, to select from a list of all vector layers available in QGIS. Layers not loaded in QGIS can be selected as well, as in the case of raster layers, but only if the algorithm does not require a table field selected from the attributes table of the layer. In that case, only opened layers can be selected, since they need to be open so as to retrieve the list of field names available. Irá ver um botão por cada seleccionador de camada vectorial, como é exibido na figura em baixo.

Figure 17.8: Vector iterator button If the algorithm contains several of them, you will be able to toggle just one of them. If the button corresponding to a vector input is toggled, the algorithm will be executed iteratively on each one of its features, instead of just once for the whole layer, producing as many outputs as times the algorithm is executed. This allows for automating the process when all features in a layer have to be processed separately. • A table, to select from a list of all available in QGIS. Non-spatial tables are loaded into QGIS like vector layers, and in fact they are treated as such by the program. Currently, the list of available tables that you will see when executing an algorithm that needs one of them is restricted to tables coming from files in dBase (.dbf) or Comma-Separated Values (.csv) formats. • Uma opção, a escolher de uma lista de selecção de uma lista de opções possíveis. • A numerical value, to be introduced in a text box. You will find a button by its side. Clicking on it, you will see a dialog that allows you to enter a mathematical expression, so you can use it as a handy calculator. Some useful variables related to ) output=SpatialPoints)

A variável polygon já contém o objecto SpatialPolygons?> Import all photograph points This command will import all of the encoding="UTF-8"?>

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