DEM Manipulation and 3-D Terrain Visualization: Techniques Used by the U.S. National Park Service

Abstract

Manipulating digital elevation model (DEM) surfaces, like pliable modelling clay, enhances the appearance and legibility of 3-D topography on maps. The U.S. National Park Service (NPS) uses the familiar image-editing tools in Adobe Photoshop to manipulate raster DEM data. Exporting modified DEM data with the help of freeware and shareware utilities allows subsequent rendering of final 3-D scenes in Corel Bryce. Techniques to be discussed include topographic substitution – a method for reverse engineering present-day landscapes into the past or projecting them into the future; selective vertical exaggeration; resolution bumping – a technique developed specifically for improving the legibility of high-mountain landscapes; painting and filtering effects; and, borrowing from the traditional masters of landform depiction, creating 3-D scenes that emulate the panoramas of Heinrich Berann and the spherical over-the-horizon views of Richard Edes Harrison by warping the projection plane of DEMS. The unique challenges of 3-D mountain mapping and the continuing pursuit of design excellence – a cornerstone of the NPS cartographic program – are overarching themes.