Improving Detail in Shaded Relief

The standard “hillshade” tool included in most GIS software suites implements a simple model of lighting with a set of assumptions that make the tool fast and easy to use. This simplified lighting model can visually degrade steep terrains, producing over-dark areas and removing important terrain detail. The underlying model can, however, be manipulated to output displays without these drawbacks. This mimics the effect of ambient light without complicating the lighting model by introducing additional light sources. This article will briefly describe the underpinnings of Lambertian shaders, then demonstrate how the traditions and assumptions built into most GIS tools can be removed to give more flexibility and control over results. Finally, shadows will be discussed as a separate addition to shaded relief.