Altitude and Relative Relief

Topography is an invariate (i.e. static) feature of the physical landscape which is described by altitude per se, as well as the rate of change of altitude over distance. As such altitude exerts major influences on macro-,meso- and microscale features of climate and hence on hydrological and agricultural responses. On a macroscale (i.e. scale of 10s to 100s of km) and mesoscale (1-10 km) altitude can act as a barrier to rainbearing air masses. In regard to temperatures, higher altitudes generally cause lowered temperatures, although the lapse rate of temperature varies with region and season.

Altitudes mapped in this Atlas are at a spatial resolution of 1 arc minute, i.e. at a grid of 1.7 x 1.7 km. Over 427 900 grid points make up the RSA, Lesotho and Swaziland. The gridded values of altitude were initially collated by the School of BEEH, who derived them from various sources. Later those values were modified and corrected with the 200 m Digital Elevation Model obtained from the Surveyor General`s office.