Once we have all the tiles loaded we need to 1) mosaic them into a single contagious dataset and 2) reproject them into an equal area projection. Skip to video.
Then under the raster menu find the merge tool.
Select all the SRTM elevation layers.
Open the Clip Raster by Extent tool.
Clip the merged elevation dataset to the Kakadu tenure shape file.
Finally, we need to reproject the Kakadu elevation layer into an equal area projection. Currently it is in a geographic projection (Lat/Long) which limits the ability to calculate areas and create other landscape datasets derived from this.
Finally right-click and remove all of the tile files and merged layers leaving only the final clipped and warped elevation.
Reclassifying Raster Data
Calculating escarpment area.
Now ‘reclassify’ the Kakadu elevation data pull out all of the up-land escarpment country.
You can use the identify features tool to get an idea of the escarpment elevation
In the processing tool box find the reclassify by table tool.
Create a table similar to that shown below. You will nee to add a new row for the upper classification limit.
Once you have reclassified the elevation data you can produce a report showing the area of each class using the Unique value report tool.
Search for this too in the tool box..
This will produce an output file that you can access through the results viewer.
Create a slope raster using the QGIS slope tool
Once you have created the new slope data set use the symbology tools to alter the display (‘band’ rendering).
- Choose singleband pseudocolor as the render type
- Scale the sundering from 0 to 40 degrees.
- Choose the colour ramp. For the ramp below I inverted the ramp using a right click on the ramp displayed.
The display should look something like this:
To make the topographic detail easier to see we will add a hillshade effect to the display.
Find the QGIS hillshade tool in in the processing toolbox
Once you have produced the Hillshade layer move it above the slope layer. Then using the transparency properties for the Hillshade change the transparency to 50%/.
You should have a slope display that looks something like this: