Introduction
A plethora of different indexes can be extracted from Digital Elevation Models (DEMs). This post covers the indexes that can be retrieved using GDALDEM.
Prerequisites
You must have a systematically tiled DEM setup with Karttur´s GeoImagine Framework. As outlined in the provious posts on elevation data in this blog.
Framework process
The Framework process for extracting indices from tiled DEMs using GDALDEM is GdalDemTiles. GdalDemTiles is just an envelop binding to GDALDEM.
Json parameterization
For the Copernicus DEM example used throughout this blog, the json parameterization for GdalDemTiles is under the button.
The json parameterization calls GdalDemTiles x times to generate the following indices:
- hillshade (radius: 1 cell)
- TPI (radius: 1, 3 cell)
- TRI (radius: 1, 3 cell)
- slope (radius: 1, 3 cell)
- aspect (radius: 1 cell)
Hillshade and aspect are only produced for a kernel with a radius of 1 cell (kernel with 3 x 3 cells). Topographic Position index (TPI), Topographic Roughness Index (TRI) and slope are produced using two different kernel radiuses, 1 and 3 cells.