DEM

http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/digital_elevation_models

DEM refers to digital elevation models. The DEM is a digital image that consists of terrain elevation data and is represented in either a 3-D image or a digital model of the Earth’s surface. The images may be colorized to bring out relief of the surface. The above is an image using DEM to show the difference in elevation across the Earth surface.