ABSTRACT
To model a piece of terrain surface, first a set of data points needs to be acquired from the surface. Indeed, data acquisition is the primary (and perhaps the single most important) stage in digital terrain modeling. For this, two stages are distinguished, that is, sampling and measurement. Sampling refers to the selection of the location while measurement determines the coordinates of the location. Sampling will be discussed in this chapter while measurement methods will be discussed in the next chapter. Three important issues related to acquired DTM source (or raw) data are density, accuracy, and distribution. The accuracy is related to measurements. The optimum density and distribution are closely related to the characteristics of the terrain surface. For example, if a terrain is a plane, then three points on any location will be sufficient. This is not a realistic assumption and, therefore, an analysis of the terrain surface precedes the discussion of sampling strategies in this chapter.
