Terrain models have always appealed to military personnel, planners, landscape
architects, civil engineers, as well as other experts in various earth sciences.
Originally, terrain models were physical models, made of rubber, plastic, clay, sand,
etc. Since the later 1950s, the computer has been introduced into this area and the
modeling of terrain surface has since then been carried out numerically or digitally,
leading to the current discipline— digital terrain modeling.