DEM (Digital Grid-Point Elevation Models) Synthesis from Three-Dimensional Cartographic Data,

Currently, topographic products such as contour, slope, and aspect are commonly derived from computer processing of digital grid-point elevation models DEM. DEMs can be laboriously created by a user from an analytical plotter equipped with profiling capability. Alternatively, a user can acquire a DEM produced by an external source, but then be constrained by the production resolution or accuracy which might not be suitable for the users application. Recently, the integration of stereoplotters with geographic information systems has resulted in limited terrain data production in X, Y, Z coordinates 3-dimensional digital cartographic data. In those cases where detailed 3-dimensional data exists, building a DEM from this database can save labor and preserve user-defined resolution and accuracy criteria. In this study, previously digitized 3-dimensional terrain data are combined and converted to a 3 arc second user-defined cell matrix. Multiple elevation data points falling into the same cell were averaged to provide a single elevation value and those cells without an elevational value were flagged. The existing elevation data could then be displayed via stereo superposition over a photographic model established on an analytical plotter and those flagged cells could be profiled. This paper presents the method involved in building a DEM from 3-dimensional cartographic data and weighs the benefits and shortfalls of this method.