In SAGA GIS (and by extension - QGIS) there is a tool called Topographic Position Index.
It is a tool that assigns an index value based upon the land form feature - ridges and peaks are assigned positive values, and valleys are assigned negative values.
In addition to this tool - there is a TPI based landform classification - which takes that Position index, and classifies the landscape into different land forms, such as:
It is a tool that assigns an index value based upon the land form feature - ridges and peaks are assigned positive values, and valleys are assigned negative values.
In addition to this tool - there is a TPI based landform classification - which takes that Position index, and classifies the landscape into different land forms, such as:
- Canyons, deeply incised streams,
- Mid-slope drainage, shallow valleys
- Upland drainage, headwaters
- U-shaped valleys
- Plains
- Open slopes
- upper slopes/messas
- local ridges/hills in valleys
- midslope ridges, small hills in plains
- Mountain tops and high ridges
If you're interested: http://www.jennessent.com/downloads/tpi-poster-tnc_18x22.pdf
Basically, I've created a QGIS style based upon the map used in the poster by A. Weiss.
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| 3D plot over OS Terrain 50 © Crown Copyright and Database Right (2017). Ordnance Survey |
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| Map view of TPI Landform Classification based on OS Terrain 50 |
The TPI Based Landform Classification is useful for determining the landform characteristics for a given area - and by classifying them into set categories, one can compare landforms in different areas.
To use the tool you need a DEM, and QGIS.
The tool is located in the Processing Toolbox under SAGA>Terrain Analysis - Morphology > TPI based landform classification
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