ABSTRACT
Traditional spatial representations are in two-dimensional (2-D) form and static mode. However, dynamic and multidimensional representations are now being more widely used.
Terrain surfaces are popularly represented in digital and 3-D forms, leading to terms such as digital terrain models (DTMs) and digital elevation models (DEMs). The DEM is normally used to refer to the digital representation of elevation values in grid form. DTM is a concept covering other information in addition to elevation in grid form. Triangular irregular network (TIN) is another form widely used in practice. DTMs, together with digital contour data, form a major part of a national spatial data infrastructure. A section in this chapter is devoted to the multi-scale representation of DTM surfaces.
