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Your First Analysis

:::caution Last revised 2026-05-01 — 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. :::

This tutorial walks you through a complete end-to-end analysis: loading a DEM, computing slope, and adding the result to the map — all from the browser.

Prerequisites​

  • FastGIS server running and accessible
  • A GRASS location containing a DEM raster (e.g. elevation)
  • Your API token

1. Connect and select an environment​

  1. Open the GRASS Runner
  2. In the Connection panel enter your Base URL and API token
  3. Click Connect & load environments
  4. Select the Location and Mapset that contain your DEM

2. Add the DEM to the map​

  1. Click the ⊞ (Add Raster) toolbar button
  2. Select elevation from the dropdown
  3. Click Add to Map

The DEM appears as a WMS layer on the Cesium globe. Use ⊕ to zoom to it.

3. Run r.slope.aspect​

  1. In the Run Module panel type r.slope.aspect
  2. Click Load ↓
  3. Fill in the form:
    • elevation → your DEM raster
    • slope → output name, e.g. slope_result
  4. Check the Command preview line
  5. Click ▶ Run

Watch the Terminal tab for output. The module completes in seconds for a small region.

4. Add the slope layer​

  1. Click ⊞ again
  2. Select slope_result from the dropdown
  3. Click Add to Map

Adjust the opacity slider in the Layer Manager to blend slope over the DEM.

5. Save your work​

Click the Save toolbar button (or use the Workspace panel to create a named session) so you can return to this state later.

Congratulations — you've run your first GRASS module in the browser! Continue with Terrain Profile to extract an elevation transect.