Hillshade: Making Terrain Look Three-Dimensional
A raw elevation raster is a flat grey gradient the eye cannot parse. Hillshade simulates the sun raking across that surface, casting the light and shadow that make ridges, valleys and drainages suddenly legible.
What it actually measures
Hillshade computes, for each cell, how brightly it would be lit given a chosen sun azimuth and altitude and the cell's own slope and aspect, returning a 0–255 grey value. It is a visualisation of the terrain, not a measurement of it.
The formula
Reading the values
0 = full shadow · 255 = fully lit for the chosen sun position.
The data it needs
| Derived from | Digital Elevation Model (SRTM / Copernicus, 30 m) — not an optical band index. |
In practice
It is the standard basemap backdrop for cartography, for archaeological and geomorphological feature detection, and for any map where readers need to feel the shape of the land.
Where it struggles
The result depends entirely on the light source — a low sun angle exaggerates relief and can hide features aligned with the light. Cartographers conventionally light from the north-west; try multi-directional hillshade to avoid missing structures.
Compute Hillshade on your own study area
Skip the code. Draw or upload a boundary and Spatial Research Suite runs Hillshade on live data — with cloud masking, exports and citations built in.
Run this analysis in GISforus →Frequently asked
Is hillshade a measurement or a visualisation?
A visualisation — it models illumination for display and changes completely with the chosen sun position; it is not a quantitative terrain variable.
What sun angle should I use for hillshade?
A north-west azimuth (~315°) at ~45° altitude is the cartographic convention; multi-directional hillshade avoids hiding features aligned with a single light.