These data sets have important applications: they allow for rapid reconstruction of contour maps per se and for plotting elevation profiles; various kinds of photogrammetric calculations are easily done with the numbers; these can be edited and filtered by image processing to enhance the display products and data sets can be merged into larger maps. Surfaces may also be presented as X-Y-Z plots (the Z dimension is shown as regularly spaced vertical lines whose lengths are proportional to elevation), in several formats:

Shaded relief maps: in which slopes are assigned different shades of gray depending on elevation, or a variant, in which shadowing is assigned to selected slopes depending on their orientation (aspect) and on sun direction and azimuth (by shifting these parameters, different renditions bring to light different surface features and trends).

Color density slices : in which elevations are color-coded.

Perspective Views: since geometric variables such as orientation and height are readily calculated from the digitized data, the surfaces can be recreated to look like oblique photos. Such surfaces are easily examined from different perspectives by rotating the view horizontally (along a vertical axis) or changing the look angle.

Draped Views: the ultimate display is usually one in which a surface image, such as a Landsat scene, is registered or "draped" onto the DEM array (data cells are matched with pixels), causing that surface and the features on it to be depicted in some form of 3-D display (e.g., in a perspective view or by creating pseudo-stereo pairs as a stereo model). Various thematic maps, as for example, land use, urban structure, or geology can also be converted into 3-D mode.

Examples of these DEM-based products abound on the Internet. We will show just a few that are typical:

Check first this gray level relief map, constructed from 1:250,000 DEM data, of the Susanville area in the Sierra Nevada Mountains:

Next, examine the variant in which shadow effects emphasize relief, by switching to a grand scale view of the entire conterminous U.S. Locate your home area.

An excellent example of a map in which the elevations are color-coded is this DEM version showing the entire state of Wyoming. The data source is a series of 30-second digitized maps. Lower areas are in green; higher in yellows, then brown.

Let's now peer at a spectacular scene looking up the Grand Canyon as shown in a perspective view developed from DEM data and artificially colorized to resemble the rock units. But first, to gain familiarity with this incredible "ditch" carved over millions of years by the Colorado River, examine this Landsat subscene (the snow-covered area is the Kaibab Plateau, some 2000 feet higher than the South Rim):

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