TABLE OF CONTENTS The concept of creating digital models of the terrain is relatively recent and the term digital terrain model (DTM) is generally attributed to two American engineers at the Massachusetts Institute of Technology during the late 1950s. The definition they coined then was: a "DTM is simply a statistical representation of the continuous surface of the ground by a large number of selected points with known X, Y, Z coordinates in an arbitrary coordinate field" (Miller and LaFlamme, 1958). Specifically, their early work was concerned with the use of cross-sectional data to define the terrain. Since then, several other terms, such as digital elevation model (DEM), digital height model (DHM), digital ground model (DGM), and digital terrain elevation data (DTED) have been combined to describe this and other closely related processes. Although in practice these terms are often presumed to be synonymous, in reality they often refer to distinct products (Petrie and Kennie, 1990). The following discussion is therefore provided in an attempt to simplify and standardize the use of these terms.
By reviewing various dictionaries and technical literature, a variety of definitions or meanings for the words and terms used in DTM are encountered. For example, ground may be defined as "the solid surface of the Earth," "a solid base or foundation," "a surface of the Earth," or "a portion of the Earth's surface." Similarly, height can have different meanings such as "measurement from base to top," "distance upward," or "the elevation above the...
