TABLE OF CONTENTS The acquisition of DTM data aims at representing the continuous surface of the Earth using a discrete set of points, which could be handled by computers. In other words, DTM acquisition is a sampling process that represents a continuous surface through a finite set of points. It should be noted that alternative sampling schemes may lead to different results both in the DTM itself and its derivatives (e.g., slope maps, aspect maps, and contour lines). Therefore, the accuracy of the individual elevations/samples is not the only criterion that controls the accuracy of derived information from a DTM. Other contributing factors include the density and the locations of the sample points relative to key surface characteristics, such as break lines, mountain peaks, and valley basins. DTM acquisition techniques have been discussed in Chapter 2.
DTM manipulation includes editing, filtering, enhancing, merging, joining, and elevation resampling. Editing the DTM data might be required to correct errors in the elevation data resulting from erroneous matches in overlapping images and/or to update portions of the DTM due to object space changes (e.g., construction of new roads, cut and fill applications). DTM filtering and/or enhancement might be used to highlight the trend or the local detail component of the surface in question. In addition, a filtering procedure might be carried out to reduce the data volume in a DTM, which in turn leads to saving disk storage space and/or efficient data processing. Merging and joining DTM data is necessary when dealing with multiple...
