Altitude and Relative Relief (standard deviation)

Relative relief (RR) is an index of the variability of the topography of an area, irrespective of whether that area is at a high or low altitude. As such, RR is also an index of the hilliness of the area. Relative relief, RR, in the context of this Atlas RR is the standard deviation (m) of the 9 point values of altitudes from a 3` x 3` block of altitudes from the 1 arc minute database of altitudes covering South Africa, with that value of RR representing the middle pixel of the block of 9.