Terrain Relief Models, Unabridged

How To
4

QGIS – Loading Your Layers

Import your data layers

  1. From the Layer menu, go down to Add Layer.
    • Click Add Raster Layer... (Ctrl-Shift-R) for raster data (e.g. elevation data).
    • Click Add Vector Layer... (Ctrl-Shift-V) for vector data (trails, Google Earth files, et cetera).
  2. Leave File as the Source Type.
  3. Click the ... button to the right of the Vector Dataset(s)/Raster Dataset(s) text box in the Source section.
  4. Choose the file containing your data and click Open.
  5. Click the Add button to add the dataset to your QGIS session.
    • Some file types, e.g. Google Earth .kml files, may be read as multiple layers. See “Importing vector files with multiple layers” for advice.
  6. If you have more of the same type of data, continue from step 3.
  7. To add data layers of the other type, choose Vector/Raster from the left side of the Data Source Manager window and continue from step 2.
  8. When you have loaded all your data layers, click Close.

Importing vector files with multiple layers

Some vector files you import may have multiple layers. You can just select them all, import everything, and just click around in the Layers box to filter through the results, but that is often not the best approach. For example, a Google Earth .kml file with trails and waypoints may be imported as one layer for each LineString (i.e. path) plus one layer for each folder of waypoints. You will almost certainly want to combine all the trails into one layer containing them all, but you cannot combine “line” layers with “point” layers. To make life easier on yourself, for each file:

  1. In the Select Vector Layers to Add... popup, click the Geometry type header to sort by geometry type.
  2. Select all the layers of one geometry type.
  3. Leave Add layers to a group checked.
  4. Click OK.
  5. From the Vector menu, go to Data Management Tools and click Merge Vector Layers...
  6. Click the ... button to the right of the Input layers box.
  7. Select all the layers you want to merge (usually the ones you’ve just imported).
  8. Click OK.
  9. If you want to keep the merged layer permanently, click the ... button to the right of the Merged box and choose Save to file...
    • Give your new file a name, and feel free to leave the type as GeoPackage (*.gpkg) unless you have reason to choose otherwise.
  10. Leave Open output file after running algorithm checked.
  11. Click the Run button. The process will run.
  12. Click the Close button to close the Merge Vector Layers window.
  13. In the Layers box (bottom left, usually), rename your new merged layer.
  14. If your new merged layer is inside the group of your source layers, drag it down and drop it out of the group.
  15. Right-click the source layers (or the group containing the source layers) and remove (so you won’t have a jumble to look through later).

Merging multiple raster layers

If you required multiple elevation data files to cover your entire area of interest, you will want to merge them into a single layer.

  1. From the Raster menu, go to Miscellaneous and click Merge...
  2. Click the ... button to the right of the Input layers box.
  3. Select the raster data layers you want to merge.
  4. If you want to keep the merged layer permanently, click the ... button to the right of the Merged box and choose Save to file...
    • Give the file a name, and select IMG files (*.img) from the Save as type: drop-down menu. (You could alternately choose another type, but IMG files, i.e. Erdas Imagine Image files, are self-contained and convenient.)
  5. Leave Open output file after running algorithm checked.
  6. Click the Run button. The process will run.
  7. Click the Close button to close the Merge Vector Layers window.
  8. In the Layers box (bottom left, usually), rename your new merged layer.
  9. Right-click the source layers and remove (so you won’t have a jumble to look through later).
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