ABSTRACT
Contour production has been one of the traditional applications of DTMs. This chapter is devoted to the production of contours from DTM.
11.1 APPROACHES FOR CONTOURING FROM DTM
Contour lines could be produced from either grid-based or triangulation-based DTM, either by a vector-based or by a raster-based method. Thus, theoretically speaking, four combinations are available for contouring from DTM:
The first two approaches are widely used. Raster-based contouring from a gridbased DTM is not widely used although it is not difficult. Raster-based contouring from a triangulation-based DTM is not practical because the triangulations are normally for irregularly distributed data and thus it is not possible to form a raster structure without interpolation. It is possible to produce a stereomate for a contour map so that a stereo model of terrain can be seen if viewed using a stereoscope. This results in various approaches for contouring from DTM, as shown in Figure 11.1.
