DEM

http://www.google.com.pe/imgres?imgurl=http://eros.usgs.gov/ecms/images/prodimages/dem.jpg&imgrefurl=http://eros.usgs.gov/Find_Data/Products_and_Data_Available/DEMs&usg=__Vew-5Hj9GehlGolpk9JmK3brwSM=&h=846&w=634&sz=204&hl=es&start=2&zoom=1&um=1&itbs=1&tbnid=Y0xo31nJCxFYSM:&tbnh=145&tbnw=109&prev=/images%3Fq%3DDEM%26um%3D1%26hl%3Des%26sa%3DG%26tbs%3Disch:1

A digital elevation model (DEM) is a representation of terrain. This type of map is commonly used when trying to illustrate ground relief.