Ouvrir un projet QGIS préexistant
Ranger la barre d’outils
In this chapter we begin using QGIS. We’ll see how to install the software and understand the layout, interface and core functions of the software. By the end of this chapter, you’ll be on your way to becoming a competent GIS user!
Note that if you have previously installed QGIS, feel free to skip ahead to section three. Otherwise, let’s start here and get QGIS installed.
Le sit de QGIS doit ressembler à ça:
à la fin du téléchargement, lancez l’installateur et suivez les instructions pour installer QGIS.
Ouvrez le répertoire dans lequel vous avez téléchargé le fichier d’installation QGIS.
Clickez J’accepte aux conditions de la licence.
QGIS will begin to install. It may take a few minutes to complete.
QGIS doit ressembler à ceci:
Next we will open up a QGIS project, and take a look at the different pieces of the QGIS interface. If you installed InaSAFE previously, make sure it is closed by clicking on the X in the upper right corner of the InaSAFE panel. If it isn’t open or you haven’t installed it yet, carry on. We will come back to this later.
This is the window where the map is shown. Our project has two different files open, one which shows districts of the Sleman regency, and another that shows the railway line running through the area. Both of these files are drawn together in the map canvas.
On the left side of QGIS is the layers list. This lists the layers, or files, that are loaded into our QGIS project. In this project, we have two layers, Kecamatan_Sleman and railway_Sleman_OSM.
The layers panel not only shows all the files that are currently open, it also determines the order that they will be drawn on the map canvas. A layer that is at the bottom of the list will be drawn first, and any layers above it will be drawn on top.
Notice how the map canvas changes. The railway layer is now shown below the district layer, and part of the railway is now obscured. A map should never show railway hidden beneath district areas, so go ahead and move the layers back.
At the top of QGIS are a large number of tools, which are contained within various toolbars. For example, the File toolbar allows you to save, load, print, and start a new project. We already used one of these tools when we opened this project.
En passant le curseur sur une icone. le nom de l’outil s’affiche pour vous aider à identifier chaque outil.
The number of tools (buttons) can seem a bit overwhelming at first, but you will gradually get to know them. The tools are grouped into related functions on toolbars. If you look closed you can see a vertical array of ten dots to the left of each toolbar. By grabbing these with your mouse, you can move the toolbar to a more convenient location, or separate it so that it sits on its own.
If you feel overwhelmed by the number of toolbars, you can customize the interface to see only the tools you use most often, adding or removing toolbars as necessary.
Let’s remove some of the toolbars that we will not be using in this training, to make the interface a bit cleaner. Right-click on the toolbar, and uncheck the boxes next to the following toolbars:
Base de données
Après avoir enlevé ces barres d’outils et en avoir déplacé, vous devriez avoir ce type d’aspect:
Even if they are not visible in a toolbar, all of your tools will remain accessible via the menus. For example, if you remove the File toolbar (which contains the Save button), you can still save your map by going to Project ‣ Save.
Barre de statut
The status bar shows information about the current map. It allows you to adjust the map scale and see the mouse cursor’s coordinates on the map.
The coordinates of this map are the same type of coordinates that are recorded by GPS devices. The status bar show shows the longitude and latitude of your mouse cursor.
Cela peut être déroutant pour l’instant, mais à mesure que vous progresserez dans votre compréhension des SIG cela vous apparaîtra familier.
Nous allons maintenant ajouter une couche vecteur contenant des routes à notre projet.
Clickez sur le bouton Ajouter une couche vecteur de la barre d’outils.
One of the most common file formats are shapefiles, which end with the extension .shp. Shapefiles are often used to save geodata, and are commonly used with GIS applications like QGIS.
We’ve already taken a look at the QGIS toolbar and seen the tools for opening a project and adding a new layer. Here’s a list of some other commonly used tools. Feel free to play around with them if you like. The important thing for now is to start getting familiar with QGIS.
Bascule en mode édition
Éditer un objet dans une couche
faire glisser la carte
|Drag the map to a new location|
|Zoom in on the map|
|Zoom out on the map|
zoomer sur l’ensemble des couches
|Zoom so that all layers fit in the map window|
Ouvrir la table d’attributs
|Open a layer’s attribute table|
|Select Single Feature||Select a feature in the selected layer|
QGIS has core functionality, which we will continue to explore in this guide, but it also allows the use of additional plugins, which allow you to add functionality to the software. Again, these plugins are free. To use them, you simply need to connect to the internet and install. To install new plugins, make sure you are connected to the internet. They first need to be downloaded, and then activated. Some plugins are already downloaded and available, and you can see them by going to Plugins ‣ Manage and Install Plugins.
This displays a list of plugins that have already been downloaded and can be activated. To enable a plugin, check the box next to it in this menu. For now, let’s leave all the plugins as they are. We’re going to download and activate a new plugin in the next section.
There are many more plugins, but they must first be downloaded. To download a plugin, click the Not installed tab. This will load available plugin repositories, and you will see a list of all available plugins for download.
Note that plugins which have already been downloaded can be activated or deactivated from the Installed tab. If it has not yet been downloaded, downloading a plugin from the Not installed tab will automatically activate it.
The OpenLayers plugin allows you to view various web maps as a layer in QGIS. This means that you can access the OSM slippy map, Google Maps and Bing Maps from within QGIS. Follow along and we’ll see how this works.
It may take a few minutes to download.
Your project should now look like this:
If you pay attention, there is something wrong with the maps. Can you guess what it is? All three layers above Bing Aerial layers should be shown on the map.
Adding a layer such as Bing Aerial will change the Coordinate Reference System, or CRS, of your project. Essentially this means that your project is not using longitude and latitude coordinates anymore. This shouldn’t affect you right now, but it will make sense later when we cover CRSes.
Now, we are going to install InaSAFE plugin.
Now you already know basic QGIS from installation, understand QGIS layout, learning useful toolbar and basic operation in QGIS. You also already learn about how to install InaSAFE, a plugin that we will learn more in the last chapter of this module.