Elevation anchoring

The model predicts height above ground (nDSM). Anchoring adds terrain so every pixel gets an absolute elevation above a datum (DSM). It is available for georeferenced scenes, in Inspector → Info → Elevation reference.

Automatic anchoring

With Anchor georeferenced results automatically on (the default), the app fetches coarse terrain tiles (AWS Terrarium) for the scene’s footprint right after each run. The product chip in the viewport shows progress and changes from nDSM to DSM when anchoring is done.

Manual options

1. Anchor to DEM (Terrain Tiles): fetch terrain tiles now.
2. Load DEM file: use your own DEM GeoTIFF instead, such as a national DEM or CartoDEM. Set Datum of a loaded DEM file:
   • EGM96 (SRTM, NASADEM)
   • EGM2008 (Copernicus GLO-30)
   • WGS84 ellipsoid (CartoDEM)
   • Not stated
3. Adjust Share of structure height already in the DEM. Coarse DEMs partly contain buildings and trees, and this slider controls how much of each structure is assumed to be in the DEM already, to avoid double counting.
4. Choose the Height reference for display and export: above ground (nDSM) or elevation (DSM).

After anchoring, File → Export → Elevation data also offers GeoTIFF nDSM and GeoTIFF DTM.

Assumptions and limits

The Info tab lists the assumptions behind the current anchoring. In short:

• the terrain is only as detailed as the DEM (about 30 m), so steep relief is smoothed;
• terrain tiles mix sources and are nominally EGM96;
• building mass already in the DEM is removed only approximately (the slider above);
• non-georeferenced (rDSM) results cannot be anchored.

Tip

For the most accurate absolute DSM, run the scene through the self-hosted service with absolute=true. It uses Copernicus GLO-30 and the DEM-anchored method, and writes a compound-CRS GeoTIFF.