Terrain & Elevation
Turn a grid of heights into slope, shade, contours and drainage.
A DEM is the one raster whose values people reason about directly, which is why terrain errors are so easy to miss: a slope map made from a geographic-CRS DEM is wrong everywhere and looks fine. These guides start with what kind of surface you actually have — ground or canopy, and measured from which zero — then derive slope and aspect, hillshade, contours, elevation profiles, flow direction and viewsheds, each with the failure that most often makes the output quietly meaningless.
If you already have a DEM and know its vertical datum and cell size, start at stage three. If you do not, the first two guides are worth twenty minutes, because a slope computed from the wrong surface or in the wrong units is wrong by orders of magnitude rather than by a little.
Start here
The cornerstone guide — the whole workflow end to end. Everything after it goes deeper into one part of it.
Step 1 Digital Elevation Models Explained: DEM, DSM and DTM dem dsm dtm explained Begin the path →The full path, in order
The concepts underneath the work, then each task, then the errors that task produces. Work down, or jump to the step you need.
- Vertical Datums Explained: Why Your Elevations Are Off vertical datum explained 🧭 Concept
- Slope and Aspect Explained: How They Are Computed from a Grid slope aspect explained 🧭 Concept
- How to Calculate Slope and Aspect from a DEM in Python calculate slope python dem ⚙️ How-To
- Slope Values Are Wrong or Absurdly Steep slope values wrong 🔧 Fix
- How to Make a Hillshade from a DEM in Python hillshade python ⚙️ How-To
- Hillshade Looks Flat, Washed Out or Inverted hillshade inverted 🔧 Fix
- How to Generate Contour Lines from a DEM in Python generate contours python ⚙️ How-To
- Contours Come Out Jagged or Full of Tiny Rings contours jagged noisy 🔧 Fix
- How to Extract an Elevation Profile Along a Line in Python elevation profile python ⚙️ How-To
- How to Fill Sinks and Derive Flow Direction from a DEM fill sinks flow direction python ⚙️ How-To
- How to Calculate a Viewshed in Python viewshed python ⚙️ How-To
Topics this path covers
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