Shaded Relief Maps
Shaded relief maps show features on the surface, such as mountains, valleys, plateaus, and canyons. Areas that are flat or have few features are smooth on the map, whereas areas with steep slopes and mountains appear more rough. The maps were generated using a computer and a database of elevations for the state. This type of database is called a Digital Elevation Model or DEM. The computer determines an average elevation for each of a number of small rectangular areas, and uses this grid of elevations to construct a virtual 3-dimensional landscape. The computer then simulates what the landscape would look like if the sun were low in the western sky (like several hours before sunset). West-facing slopes, which would be in the sun, are shown brighter than east-facing slopes, which would be shaded. The resulting light-dark pattern causes the 3D illusion.
The maps also use colors to show variations in elevation (height above sea level). The main relief maps of Arizona use red and purple for low areas, brown and green for intermediate elevations, and orange and pink for the highest parts of the state.
The shaded relief map used in the Arizona Geology Virtual Tourist is modified
from an original by Ray Sterner of Johns Hopkins University.
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