Land Resources

Global Terrain Slope and Aspect Data

The global terrain slope and aspect database has been compiled using elevation data from the Shuttle Radar Topography Mission (SRTM). The SRTM data is publicly available as 3 arc second (approximately 90 meters resolution at the equator) DEMs (CGIAR-CSI, 2006).

The high resolution SRTM data have been used for calculating:

  1. Terrain slope gradients and classes for each 3 arc-sec grid cell;
  2. Aspect of terrain slopes for each 3 arc-sec grid cell;
  3. Distributions of slope gradient and slope aspect classes for 30 arc second grid.

The SRTM data cover globe areas up to 60° latitude. For the remaining area elevation data from GTOPO30 (USGS, 2002) were used.

A global terrain slope and aspect database comprises the following elements.

  • Elevation (median)
  • Slope gradient: Distributions of nine slope gradient classes are available for each grid-cell: 0–0.5%, 0.5–2%, 2–5%, 5–8%, 8–16%, 16–30%, 30–45%, and > 45%. 
  • Slope aspects: Slope aspect data is stored in distributions of five classes namely: Class 1:  slopes below 2% undefined aspect; Class 2: slopes facing North (315°–45°); Class 3: East (45°–135°); Class 4: South (135°–225°), and Class 5: West (225°–315°).

Additional Data documentation

Data Citation
Fischer, G., F. Nachtergaele, S. Prieler, H.T. van Velthuizen, L. Verelst, D. Wiberg, 2008. Global Agro-ecological Zones Assessment for Agriculture (GAEZ 2008). IIASA, Laxenburg, Austria and FAO, Rome, Italy.

Data format Information

Data Format Information