2.3. Lesson: Navigating the Map Canvas

Dieser Abschnitt behandelt grundlegende Navigationswerkzeuge in QGIS, die zur Navigation in der Kartenansicht genutzt werden. Diese Werkzeuge erlauben es die Kartenlayer in verschiedenen Maßstäben visuell zu erkunden.

Ziel dieser Lerneinheit: Lerne die Werkzeuge Pan und Zoom in QGIS zu nutzen und lerne etwas über Kartenmaßstäbe.

2.3.1. basic Follow Along: Basic Navigation Tools

Before learning how to navigate within the Map Canvas, let’s add some layers that we can explore during this tutorial.

  1. Open a new blank project and using the steps learnt in Create a Map, load the previously seen protected_areas, roads and buildings layers to the project. The result view should look similar to the snippet in Abb. 2.8 below (colors do not matter):

    ../../../_images/roads_buildings_added.png

    Abb. 2.8 Protected areas, roads and buildings added

Let’s first learn how to use the Pan Tool.

  1. In the Map Navigation Toolbar, make sure the pan Pan button is activated.

  2. Move the mouse to the center of the Map Canvas area.

  3. Left-click and hold, and drag the mouse in any direction to pan the map.

Next, let’s zoom in and take a closer look at the layers we imported.

  1. In the Map Navigation Toolbar, click on the zoomIn Zoom In button.

  2. Move your mouse to approximately the top left area of where there is the highest density of buildings and roads.

  3. Left click and hold.

  4. Then drag the mouse, which will create a rectangle, and cover the dense area of buildings and roads (Abb. 2.9).

    ../../../_images/zoom_in.png

    Abb. 2.9 Zoom in

  5. Release the left click. This will zoom in to include the area that you selected with your rectangle.

    ../../../_images/zoomed_in.png

  6. To zoom out, select the zoomOut Zoom Out button and perform the same action as you did for zooming in.

As you pan, zoom in, or zoom out, QGIS saves these views in a history. This allows you to backtrack to a previous view.

  1. In the Map Navigation Toolbar, click on zoomLast Zoom Last button to go to your previous view.

  2. Click on zoomNext Zoom Next button to proceed to move forward in your history.

Sometimes after exploring the data, we need to reset our view to the extent of all the layers. Instead of trying to use the Zoom Out tool multiple times, QGIS provides us with a button to do that action for us.

  1. Click on the zoomFullExtent Zoom Full Extent button.

As you zoomed in and out, notice that the Scale value in the Status Bar changes. The Scale value represents the Map Scale. In general, the number to the right of : represents how many times smaller the object you are seeing in the Map Canvas is to the actual object in the real world.

../../../_images/map_scale1.png

You can also use this field to set the Map Scale manually.

  1. In the Status Bar, click on the Scale textfield.

  2. Type in 50000 and press Enter. This will redraw the features in the Map Canvas to reflect the scale you typed in.

  3. Alternatively, click on the options arrow of the Scale field to see the preset map scales.

    ../../../_images/map_scale_options.png

  4. Select 1:5000. This will also update the map scale in the Map Canvas.

Now you know the basics of navigating the Map Canvas. Check out the User Manual on Zooming and Panning to learn about alternative ways of navigating the Map Canvas.

2.3.2. In Conclusion

Knowing how to navigate the Map Canvas is important, as it allows one to explore and visually inspect the layers. This could be done for initial data exploration, or to validate output of a spatial analysis.