TABLE OF CONTENTS Mapping and engineering applications of terrain data often involve some type of spatial analysis and data manipulation. The types of analysis and the degree of manipulation will vary with the application, but the techniques span the range of simple visualization to applications of highly sophisticated mathematical models to the terrain data to derive additional data forms.
Visualization techniques can assist the user in making instantaneous decisions and generally involve little to no data manipulation (Bailey and Gatrell, 1995). Visually fusing or combining the terrain data graphically with other datasets can go even further to providing desirable information. Analyses involving slightly more sophisticated manipulations of the data include first- or second-order derivatives of the terrain. Examples include slope and curvature and are the results of applying mathematical equations to create new datasets from the terrain. This chapter will examine some popular visualization techniques for terrain data and some of the more commonly used first- and second-order derivatives of terrain.
There are a number of basic ways to enhance and display DTM data. These basic techniques can also be combined to create additional display techniques. Other datasets that may be unrelated to the terrain (such as land cover) can be graphically combined or fused with the terrain data to provide information on environmental processes. This latter type of visualization is explored further in Chapter 8.
A basic and first step in visualizing DTMs involves assigning a gray value, or brightness value g i,...
