Digital elevation data comes from a variety of sources, the most widespread being stereo imagery from airborne or satellite instruments. In two images of the ground acquired from different points along a flight path, features are displaced differently depending on their elevation; these displacements are used to compute the elevations on a regular grid of cells, one elevation per cell, with the resulting resolution limited by the resolution of the imagery. There are pre-existing grids with global extent, such as SRTM, and regional models for specific countries, states, or other regions. While often free and ready-made, these can require special software and expertise to use.

In some areas there is no stereo imagery nor pre-existing grids of adequate resolution. In these cases, it is possible to build an elevation grid from scanned paper contour maps. The process of interpolating elevations from digitized contour lines can yield very good results, though the quality and resolution depend on the scale of the map, contour interval, and relief.

All Terrain Digital produces elevation grids from satellite data, or we can provide pre-existing elevation models. Alternatively, we have extensive experience digitizing paper maps in many parts of the world and can provide cost-effective results using this approach. Regardless of the source, we can deliver standard and custom surface products derived from the elevation data, and deliver it in a wide variety of ready-to-use formats.