Relief map is the representation of height variation with three dimensional structure. There are several techniques to produce relief maps based on psychological effect. The basic idea is that human eye will reorganize the three dimensional senses or distance of depth if there is shade or shadow projected by an illumination with the azimuth of north west (or from left upper) and the elevation of 45 degree as explained in 3-8 in this book.

Following techniques are used in many parts of GIS applications.

Contour map with shade: thickness of contour lines of southeast faced slope is increased, which results in the relief effect.

Hill shading with hatched lines: traditional cartographic representation which is manually produced by professional cartographers.

Prism map: a kind of bird’s eye view with constant height with respect to the polygon.

Shaded image: hill shading effect of cosine of angle between normal vector of the surface and the incident light.

Stereoscopic view: 3D vision can be seen stereoscopically with a pair of stereo images which have horizontal parallaxes depending on the height or depth distance.

Figure 6.8 shows some examples of relief map.