GIS-02 GIS Concepts

Owned by Antony Scott (Deactivated)
Last updated: 15 Mar, 2023
3 min read

2. GIS Concepts

In this module, you will work in the QGIS desktop GIS application to explore GIS data in various forms.

2.1. Open QGIS and load data

  1. In AppStream, launch QGIS 3.28 from the applications menu

  2. In the main menu, go to Project > Save, and save your project (even though there’s nothing in it yet) in your Home Folder

  3. Load your first layer:

    1. In the menu, go to Layer > Add Layer > Add Vector Layer and under Source, use the three dots on the right to navigate to one of the layers you downloaded in the previous exercise (if you didn’t manage to download any data, navigate to Home Folder > QGIS Training > Data > Vector and use any of the .shp files)

    2. In the Data Source Manager dialog, click Add to add load the layer, then Close

  4. You should now be seeing your data listed in the Layers panel on the left, and displayed on the map canvas on the right

  5. Use your mouse to pan and zoom (with the mouse wheel) the layer

  6. Load some base data:

    1. Go to Layer > Add Layer > Add XYZ Layer and select OpenStreetMap under XYZ Connections

    2. The OpenStreetMap base map will appear in the layer list and map canvas

  7. Drag and drop the layers in the layer list to change the order, and to see the effect layer ordering has on visibility

  8. Save the project using the Save button in the toolbar

You have now created your first map, with a vector and a base map layer! We are now going to look at the data behind the vector layer you have loaded.

2.2. Working with Attributes

Behind every vector data layer is an attribute table - have a look at this now.

  1. Click on one of the vector layers in the Layers panel, then right-click > Open Attribute Table

  2. The attribute table for the layer will appear

  3. Navigate around the table, including scrolling to the right so see all columns if necessary

  4. Click on a column heading to sort by that column

  5. Click on a row number to highlight (select) the row - you should see the geographical feature which the row corresponds to also highlighted on the map (if you can’t, find the Zoom map to the selected rows button in the toolbar and click it)

  6. Hover over the buttons in the Attribute Table toolbar to get an idea of some of the things you can do

  7. To see the attributes for a single feature, in the main menu, go to View > Identify features (or find the Identify Features toolbar button) - your cursor should now have an 'i' next to it

  8. With a vector layer in the layer list highlighted, click on a geographical feature on the map - you will see all its attribute values displayed in the Identify Results panel

  9. Save the project

You should now have a feel for vector layers, and how they are handled in a GIS application.

2.3. Loading Raster Data

We are now going to load a raster data layer.

  1. In the main menu, go to Layer > Add Layer > Add Raster Layer

  2. Under Source, navigate to Home Folder\QGIS Training\Data\raster\1250K, and select one or the .tif files and click Open

  3. In the Data Source Manager dialog, click Add then Close

  4. You may not be able to see the new layer - if that’s the case, right-click on the layer and select Zoom to Layer

  5. The new layer should now be centred in the map canvas

  6. Zoom in and out to find an appropriate viewing scale - notice that the Scale indicator at the bottom of the screen show the current scale, and can also be used to set the scale

  7. Navigate to one of the edges of the image you have loaded - you should see the OpenStreetMap layer behind it, with features such as roads and railways corresponding at the join

  8. Save the project

You have now created a simple map which includes:

  • File-based vector data

  • File-based raster data

  • Internet-based base raster data (the OpenStreetMap layer)