Shown below on the left is the black and white DEM image of Antarctica at a compressed spatial resolution (5km). The lower elevations are dark (sea level is black) and the higher ones are bright (4000 meters and above are white). The Pacific Ocean is on the lower left side of the image; the Atlantic Ocean on the upper left; and the Indian Ocean on the upper right. This image is presented in spatially compressed mode for comparison with both the shaded relief and color coded images. However, keep in mind that the full resolution DEMs were used to generate the AVHRR stereo image shown at the bottom of the page.
The image shown on the right was generated using the spatially compressed DEM data shown on the left. A DEM can be used as input to various enhancement and analysis procedures. One of these procedures allows us to generate a 'shaded relief' image with the sun positioned at any desired elevation and azimuth. A shaded relief image enhances the topographic structure in the data and can be used to extract spatial information dealing with surface fractures, faults, folds, and drainages. Several major landmarks can be seen in this image, including the Transantarctic Mountains, Ross and Ronne Ice Shelves, and the Antarctic Peninsula.
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The image below on the left was generated using both the DEM and shaded relief images shown above. By digitally combining the two image products, both the elevation and structural information can be displayed on a single image. The DEM data were color-coded to cover the elevation range from zero to 4000 meters. Notice the large elevation changes along the coastline and ice shelf edges; these are areas where the 3-D is the most dramatic when viewed in stereo. The high elevation at the center of Antarctica can easily be seen; pink areas have elevations either at or slightly above 4000 meters (13,123 feet).
The image on the right is a compressed version of the AVHRR mosaic, and is shown for comparison with the DEM. Notice the ice shelf areas, as well as the other major topographic features on both images.
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Once a DEM is digitally merged with satellite images, there are several manipulation procedures that can be used to help with the visualization and interpreteation of the data. Shown below are two data manipulation procedures aimed at enhancing the visualization of both the topographic and spectral information. The first shows three different perspective views of the AVHRR color image, and the second shows the black and white AVHRR image in stereo/3-D.
Using the DEM data, perspective views can be generated of the AVHRR image to simulate viewing the image from any direction and/or distance. The three images shown represent views toward the Ross Ice Shelf/McMurdo Sound region, the Amery Ice Shelf region, and the Ronne Ice Shelf/Ellsworth Mountains region.
2x Zoom Images: This section presents selected areas which were expanded to 2 times full resolution. 2x zoom images shown are of the McMurdo Sound, Ellsworth Mountains, and Jutulstraumen regions.
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