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Iniciando

This chapter gives a quick overview of installing QGIS, some sample data from the QGIS web page, and running a first and simple session visualizing raster and vector layers.

Instalação

Installation of QGIS is very simple. Standard installer packages are available for MS Windows and Mac OS X. For many flavors of GNU/Linux, binary packages (rpm and deb) or software repositories are provided to add to your installation manager. Get the latest information on binary packages at the QGIS website at http://download.qgis.org.

Instalação à partir da fonte

If you need to build QGIS from source, please refer to the installation instructions. They are distributed with the QGIS source code in a file called INSTALL. You can also find them online at http://htmlpreview.github.io/?https://raw.github.com/qgis/QGIS/master/doc/INSTALL.html

Instalação no dispositivo de armazenamento externo

QGIS allows you to define a --configpath option that overrides the default path for user configuration (e.g., ~/.qgis2 under Linux) and forces QSettings to use this directory, too. This allows you to, for instance, carry a QGIS installation on a flash drive together with all plugins and settings. See section Menu Sistema for additional information.

Amostra de Dados

O guia de utilizador contém exemplos baseados no conjunto de amostra de dados do QGIS.

win The Windows installer has an option to download the QGIS sample dataset. If checked, the data will be downloaded to your My Documents folder and placed in a folder called GIS Database. You may use Windows Explorer to move this folder to any convenient location. If you did not select the checkbox to install the sample dataset during the initial QGIS installation, you may do one of the following:

nix osx For GNU/Linux and Mac OS X, there are not yet dataset installation packages available as rpm, deb or dmg. To use the sample dataset, download the file qgis_sample_data as a ZIP archive from http://download.osgeo.org/qgis/data/qgis_sample_data.zip and unzip the archive on your system.

The Alaska dataset includes all GIS data that are used for examples and screenshots in the user guide; it also includes a small GRASS database. The projection for the QGIS sample dataset is Alaska Albers Equal Area with units feet. The EPSG code is 2964.

PROJCS["Albers Equal Area",
GEOGCS["NAD27",
DATUM["North_American_Datum_1927",
SPHEROID["Clarke 1866",6378206.4,294.978698213898,
AUTHORITY["EPSG","7008"]],
TOWGS84[-3,142,183,0,0,0,0],
AUTHORITY["EPSG","6267"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9108"]],
AUTHORITY["EPSG","4267"]],
PROJECTION["Albers_Conic_Equal_Area"],
PARAMETER["standard_parallel_1",55],
PARAMETER["standard_parallel_2",65],
PARAMETER["latitude_of_center",50],
PARAMETER["longitude_of_center",-154],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
UNIT["us_survey_feet",0.3048006096012192]]

If you intend to use QGIS as a graphical front end for GRASS, you can find a selection of sample locations (e.g., Spearfish or South Dakota) at the official GRASS GIS website, http://grass.osgeo.org/download/sample-data/.

Sessão Amostra

Now that you have QGIS installed and a sample dataset available, we would like to demonstrate a short and simple QGIS sample session. We will visualize a raster and a vector layer. We will use the landcover raster layer, qgis_sample_data/raster/landcover.img, and the lakes vector layer, qgis_sample_data/gml/lakes.gml.

Iniciar o QGIS

  • nix Start QGIS by typing “QGIS” at a command prompt, or if using a precompiled binary, by using the Applications menu.
  • win Inicie o QGIS usando o menu Iniciar ou o atalho do ambiente de trabalho, ou faça duplo clique no ficheiro de projecto QGIS.

  • osx Faça duplo clique no ícone na sua pasta de Aplicações.

Carregue camadas vectoriais ou raster a partir do conjunto de amostras de dados

  1. Clique no ícone mActionAddRasterLayer Carregar Raster

  2. Browse to the folder qgis_sample_data/raster/, select the ERDAS IMG file landcover.img and click [Open].
  3. If the file is not listed, check if the Files of type selectstring combo box at the bottom of the dialog is set on the right type, in this case “Erdas Imagine Images (*.img, *.IMG)”.
  4. Agora clique no ícone mActionAddOgrLayer Carregar Vector

  5. radiobuttonon File should be selected as Source Type in the new Add vector layer dialog. Now click [Browse] to select the vector layer.
  6. Browse to the folder qgis_sample_data/gml/, select ‘Geography Markup Language [GML] [OGR] (.gml,.GML)’ from the Files of type selectstring combo box, then select the GML file lakes.gml and click [Open]. In the Add vector layer dialog, click [OK]. The Coordinate Reference System Selector dialog opens with NAD27 / Alaska Alberts selected, click [OK].
  7. Amplie um pouco até à sua área favorita com alguns lagos.

  8. Faça duplo clique na camada lakes da legenda do mapa para abrir o diálogo Propriedades

  9. Click on the Style tab and select a blue as fill color.
  10. Click on the Labels tab and check the checkbox Label this layer with checkbox to enable labeling. Choose the “NAMES” field as the field containing labels.
  11. To improve readability of labels, you can add a white buffer around them by clicking “Buffer” in the list on the left, checking checkbox Draw text buffer and choosing 3 as buffer size.
  12. Click [Apply]. Check if the result looks good, and finally click [OK].

You can see how easy it is to visualize raster and vector layers in QGIS. Let’s move on to the sections that follow to learn more about the available functionality, features and settings, and how to use them.

Starting and Stopping QGIS

In section Sessão Amostra you already learned how to start QGIS. We will repeat this here, and you will see that QGIS also provides further command line options.

  • nix Assuming that QGIS is installed in the PATH, you can start QGIS by typing qgis at a command prompt or by double clicking on the QGIS application link (or shortcut) on the desktop or in the Applications menu.
  • win Inicie o QGIS usando o menu Iniciar ou o atalho do ambiente de trabalho, ou faça duplo clique no ficheiro de projecto QGIS.

  • osx Double click the icon in your Applications folder. If you need to start QGIS in a shell, run /path-to-installation-executable/Contents/MacOS/Qgis.

To stop QGIS, click the menu option nix win File osx QGIS ‣ Quit, or use the shortcut Ctrl+Q.

Opções da Linha de Comandos

nix QGIS supports a number of options when started from the command line. To get a list of the options, enter qgis --help on the command line. The usage statement for QGIS is:

qgis --help
QGIS - 2.6.0-Brighton 'Brighton' (exported)
QGIS is a user friendly Open Source Geographic Information System.
Usage: /usr/bin/qgis.bin [OPTION] [FILE]
OPTION:
      [--snapshot filename]   emit snapshot of loaded datasets to given file
      [--width width] width of snapshot to emit
      [--height height]       height of snapshot to emit
      [--lang language]       use language for interface text
      [--project projectfile] load the given QGIS project
      [--extent xmin,ymin,xmax,ymax]  set initial map extent
      [--nologo]      hide splash screen
      [--noplugins]   don't restore plugins on startup
      [--nocustomization]     don't apply GUI customization
      [--customizationfile]   use the given ini file as GUI customization
      [--optionspath path]    use the given QSettings path
      [--configpath path]     use the given path for all user configuration
      [--code path]   run the given python file on load
      [--defaultui]   start by resetting user ui settings to default
      [--help]                this text

FILE:
  Files specified on the command line can include rasters,
  vectors, and QGIS project files (.qgs):
   1. Rasters - supported formats include GeoTiff, DEM
      and others supported by GDAL
   2. Vectors - supported formats include ESRI Shapefiles
      and others supported by OGR and PostgreSQL layers using
      the PostGIS extension

Tip

Exemplo do Uso dos argumentos da linha de comandos

You can start QGIS by specifying one or more data files on the command line. For example, assuming you are in the qgis_sample_data directory, you could start QGIS with a vector layer and a raster file set to load on startup using the following command: qgis ./raster/landcover.img ./gml/lakes.gml

Opção da linha de comandos --snapshot

Esta opção permite que possa criar uma captura de ecrã no formato PNG da vista actual. Isto vem a calhar quando tem vários projectos e quer gerar capturas de ecrã dos seus dados.

Currently, it generates a PNG file with 800x600 pixels. This can be adjusted using the --width and --height command line arguments. A filename can be added after --snapshot.

Opção da linha de comandos --lang

Based on your locale, QGIS selects the correct localization. If you would like to change your language, you can specify a language code. For example, --lang=it starts QGIS in italian localization. A list of currently supported languages with language code and status is provided at http://hub.qgis.org/wiki/quantum-gis/GUI_Translation_Progress.

Opção da linha de comandos --project

Starting QGIS with an existing project file is also possible. Just add the command line option --project followed by your project name and QGIS will open with all layers in the given file loaded.

Opção da linha de comandos --extent

To start with a specific map extent use this option. You need to add the bounding box of your extent in the following order separated by a comma:

--extent xmin,ymin,xmax,ymax

Opção da linha de comandos --nologo

This command line argument hides the splash screen when you start QGIS.

Opção da linha de comandos --noplugins

If you have trouble at start-up with plugins, you can avoid loading them at start-up with this option. They will still be available from the Plugins Manager afterwards.

Command line option --customizationfile

Using this command line argument, you can define a GUI customization file, that will be used at startup.

Opção da linha de comandos --nocustomization

Using this command line argument, existing GUI customization will not be applied at startup.

Opção da linha de comandos --optionspath

You can have multiple configurations and decide which one to use when starting QGIS with this option. See Opções to confirm where the operating system saves the settings files. Presently, there is no way to specify a file to write settings to; therefore, you can create a copy of the original settings file and rename it. The option specifies path to directory with settings. For example, to use /path/to/config/QGIS/QGIS2.ini settings file, use option:

--optionspath /path/to/config/

Opção da linha de comandos --configpath

This option is similar to the one above, but furthermore overrides the default path for user configuration (~/.qgis2) and forces QSettings to use this directory, too. This allows users to, for instance, carry a QGIS installation on a flash drive together with all plugins and settings.

Command line option --code

This option can be used to run a given python file directly after QGIS has started.

For example, when you have a python file named load_alaska.py with following content:

from qgis.utils import iface
raster_file = "/home/gisadmin/Documents/qgis_sample_data/raster/landcover.img"
layer_name = "Alaska"
iface.addRasterLayer(raster_file, layer_name)

Assuming you are in the directory where the file load_alaska.py is located, you can start QGIS, load the raster file landcover.img and give the layer the name ‘Alaska’ using the following command: qgis --code load_alaska.py

Projectos

The state of your QGIS session is considered a project. QGIS works on one project at a time. Settings are considered as being either per-project or as a default for new projects (see section Opções). QGIS can save the state of your workspace into a project file using the menu options Project ‣ mActionFileSave Save or Project ‣ mActionFileSaveAs Save As....

Load saved projects into a QGIS session using Project ‣ mActionFileOpen Open..., Project ‣ New from template or Project ‣ Open Recent ‣.

If you wish to clear your session and start fresh, choose Project ‣ mActionFileNew New. Either of these menu options will prompt you to save the existing project if changes have been made since it was opened or last saved.

O tipo de informação guardado num ficheiro de projecto inclui:

  • Camadas adicionadas

  • Propriedades da Camada, incluindo a simbolização

  • Projecção para a vista do mapa

  • Última extensão visualizada

The project file is saved in XML format, so it is possible to edit the file outside QGIS if you know what you are doing. The file format has been updated several times compared with earlier QGIS versions. Project files from older QGIS versions may not work properly anymore. To be made aware of this, in the General tab under Settings ‣ Options you can select:

  • checkbox Avisar para guardar o projecto e alterações de fontes de dados quando necessário

  • checkbox Avisar quando abrir um projecto guardado com uma versão antiga do |qg|

Whenever you save a project in QGIS 2.2 now a backup of the project file is made.

Ficheiro de Saída

There are several ways to generate output from your QGIS session. We have discussed one already in section Projectos, saving as a project file. Here is a sampling of other ways to produce output files:

  • A opção do menu Projecto ‣ mActionSaveMapAsImage Guardar como Imagem abre um diálogo de ficheiro onde pode seleccionar nome, caminho e tipo de imagem (formato PNG ou JPG). Um ficheiro world file com a extensão PNGW ou JPGW é guardado na mesma pasta georeferenciando a imagem.

  • Menu option Project ‣ DXF Export ... opens a dialog where you can define the ‘Symbology mode’, the ‘Symbology scale’ and vector layers you want to export to DXF.
  • Menu option Project ‣ mActionNewComposer New Print Composer opens a dialog where you can lay out and print the current map canvas (see section Compositor de Impressão).