Meratyn

Manual/Tutorials

Terrain Analysis

This tutorial derives terrain products from a digital elevation model (DEM): a hillshade, a slope map, and contour lines. It uses the Raster tools under Processing → Raster.

Explore visibility from the map

For a quick, exploratory line-of-sight view, right-click a location and open Quick analysis → Viewshed from here. Meratyn samples the same Terrarium terrain tiles used by the map, computes the visible cells in a short-lived Web Worker, and adds the result as a translucent image layer. The 2 km, 5 km, and 15 km presets are intentionally bounded so a click cannot trigger an unbounded download or calculation. The result is saved with the project and can be reordered, hidden, or removed like any other image overlay.

This is a visual planning aid: it does not model atmospheric refraction or Earth curvature. For survey-grade work, load a DEM and use the Whitebox Viewshed tool instead. Viewsheds are currently available for Earth projects; the action is disabled for projects using a planetary ellipsoid until a matching planetary DEM source is available.

Browser or desktop Supported raster operations run in the browser. Use the desktop app when the workflow needs a native file path or an operation outside the browser engine; its optional Python sidecar handles those cases.

1. Load a DEM

Add an elevation raster as a layer, for example a GeoTIFF or COG DEM (see Adding Data). The raster tools take a file path in and write a file path out, so a local or accessible raster works best.

2. Hillshade

  1. Open Processing → Raster → Hillshade.
  2. Choose the DEM as input and set the azimuth, altitude, and z-factor if you want to adjust the lighting.
  3. Run it. The shaded-relief raster is added to the map. Place it under your other layers and lower their opacity for a relief backdrop.

3. Slope and aspect

  • Processing → Raster → Slope computes steepness from the DEM.
  • Processing → Raster → Aspect computes the compass direction of the steepest slope.

Run either against the DEM and style the output with a colormap. Open the Colorbar from the Map menu to show the value scale.

4. Contours

  1. Open Processing → Raster → Contour.
  2. Choose the DEM and set the contour interval (the elevation difference between lines).
  3. Run it to generate contour lines as a vector layer, which you can label and style like any vector data.

5. Clip to an area of interest

To restrict outputs to a study area, use Processing → Raster → Clip by extent (a bounding box) or Clip by mask layer (a vector mask). See Processing Tools.

Next steps

  • Convert raster outputs to vectors with Polygonize, or write a Raster to COG for sharing. See Cloud-Native Data.
  • Animate a time series of rasters with the Time Slider plugin. See Data Integrations.