Ruggedness is defined here as the maximum elevational difference among the nine 30''gridpoints in a 2’30'' pixel of WORLDCLIM. If the difference between the lowest and highest of the nine 30'' grid point exceeds 200 m, the 2’ 30'' pixel (this is the resolution the MB Portal operates) belongs to mountain terrain, as a matter of convention. We strongly recommend not to change it for download, to arrive at comparative studies.

Elevation belt is elevation above sea level (m) (from SRTM). To avoid climatic bias along the latitudinal gradient, better use thermal belts, or restrict elevational belts only on a regional scale (e.g. at the highest zoom level)

Thermal belts are based on temperature data from WORLDCLIM. Thermal belts seperate elevational life zones by temperature only, permitting global comparisons across latitudes.

A note of caution: Accuracy of any analysis increases with the number of grid points included. Hence, best results are obtained for large areas across which local deviations from reality of both topography criteria (ruggedness) and climate data become less significant. Errors are largest for individual point data, because, at the given resolution, these may deviate from the nearest grid point by kilometers of elevation, in the case of steep mountain flanks. The boundary of mountains adjacent to lowland is not more accurate than 30'' (c. 0.9 km at the equator).