 DEMs are commonly built using data collected using remote sensing techniques, but they may also be built from land surveying.The digital elevation model itself consists of a matrix of numbers, but the data from a DEM is often rendered in visual form to make it understandable to humans.This visualization may be in the form of a contoured topographic map, or could use shading and false color assignment (or "pseudo-color") to render elevations as colors (for example, using green for the lowest elevations, shading to red, with white for the highest elevation.