About the Cover
The cover shows six images of the same geographic area, demonstrating various GIS
data formats, depicting both natural and human-made features. The scene is a river
flowing through a canyon. North of the river is a water filtration plant. The top scene is a
TIN (Triangulated Irregular Network) indicating the elevation of the surface. Across the
bottom of the cover, left to right, the first two images are portions of (a) a DRG (Digital
Raster Graphics) file digitized from a US Geological Survey 7.5 minute quadrangle and
(b) a DEM (Digital Elevation Model). The last two images, left to right are (d) a raster-
based (cell-based, grid-based) depiction of different types of land cover and (e) a DOQ
(Digital Ortho Quadrangle), which is an aerial photograph that has been rectified so it
can be used as a map. In the center at the bottom is (c) a three-dimensional view in which
ArcGIS software was used to “drape” a DOQ over an elevation model. The red dots along
the river depict points collected by a GPS (Global Positioning System) receiver on a boat
moving along the river.
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