About the Cover: The cover illustration was made by combining three different U.S. Geological Survey digital data sets: a black and white digital orthophotograph, a digital elevation model, and a digital raster image of a topographic map. The observer viewpoint is at an altitude of 1200' above the surface, in the vicinity of Massanutten Mountain, just east of Harrisonburg, VA. The colored lines and areas from the topographic map are transparent so that when combined, the underlying imagery is visible. These data sets are then draped over a surface generated from the digital elevation data. The cover illustrates the flexibility available to the cartographer in creating graphics using computer technology and digital data sets.