Terrain Visualization- 3D Information in a 2D Map

Maps which include 3-dimensional information are ubiquitous, and not just in the form of those that employ stereoscopic effects for the wearer of the right special glasses- 3 dimensions are regularly portrayed on a 2-dimensional surface with the use of contour lines, hillshading, and hypsometric tinting.  The purpose of these techniques is to allow the viewer to more accurately visualize the varied elevations and land formations within the mapped area.

Hillshading, in particular, can provide a great deal of detailed visual information, which is readily apparent to even a map user unfamiliar with the finer points of deciphering contour lines.  Above are two hillshaded images of the same overhead view- the left image is created with shading that imitates a light source located in approximately the sun's position for this area on the 15th of January at 8 am.  The right uses the shading created by a light source in a particular position and elevation, one which is a default within ArcGIS.  Thought these two images use the same color scheme- that is, the same colors in both for high and low elevation values- it's apparent that the visual images given by each are quite disparate.  It could be contended that the image on the right, with the default light source position, gives a more readily interpreted picture.  The depression in the terrain made by the canyon is immediately evident, outlined with the darker red/brown shadows in the mostly yellow terrain.  The left image could easily be misinterpreted to be depicting a series of hills, in yellow, rising out of the terrain shaded in darker red/brown.  Clearly, the light source's position is an important consideration in the creation of a hillshaded image- and is not always best-placed in the "accurate to earth" location.