Terrain Builder
:::caution Last revised 2026-05-02 — not re-verified
This page has not been checked against the running system since it was
written, and predates a large part of the current product. It is scheduled
for rewrite. For anything about the API, /docs on a running server is
authoritative.
:::
The Terrain Builder converts a GRASS DEM raster into a Cesium quantized-mesh terrain that can be applied to the 3D globe.
Opening the panel
Click the Terrain toolbar button in the map viewer to open the Terrain Builder section in the left sidebar.
Building a terrain
| Field | Description |
|---|---|
| Input raster (DEM) | The GRASS raster to use as the elevation source |
| Name | Output dataset name — letters, digits, hyphens, underscores |
| Max depth | Tile zoom depth (1–20, default 14 — finer = more detail, longer build) |
| Overwrite | Replace an existing dataset with the same name |
Click Build Terrain to start. A progress indicator shows the current stage (export → reproject → terrain → done). Build output is streamed in real time.
Applying a terrain
When the build finishes the Apply to Globe button becomes active. Click it to load the quantized-mesh terrain into the Cesium viewer. Click Clear Terrain to revert to the default ellipsoid.
Built terrain datasets
The Built terrain datasets list shows every terrain that has already been built and is ready to serve. Each row has:
| Button | Action |
|---|---|
| Apply | Load this terrain onto the Cesium globe |
| ✕ (red) | Delete the terrain — prompts for confirmation, then removes tiles from disk |
Deleting the currently active terrain automatically reverts the globe to the ellipsoid without leaving stale tile requests.
Vertical exaggeration
The Vertical exaggeration slider (0.1 × – 5 ×) scales the terrain height in the viewer in real time. It applies to any active terrain provider including the default ellipsoid. Use values above 1 to emphasise relief in flat areas, or below 1 to flatten steep terrain.