Using sophisticated so-called "photogrammetric" techniques and computer software, a lunar terrain model can be created combining several images that show similar areas from slightly different angles. LROC's wide angle camera (WAC) has a ground resolution of approximately 100 m/pixel from LRO's nominal orbit altitude of 65 km. The camera is taking image swaths 70 km wide along LRO's ground-track. Therefore, images from adjacent orbits show substantial overlap and strong stereo effects in the overlapping images. Image overlap amounts to approximately 50 percent near the equator.
This image shows a Digital Terrain Model (DTM) of the large Orientale Basin (1,100 km diameter, about 684 miles), located on the western hemisphere of the moon, produced from stereo images obtained by LRO's Wide-Angle Camera, part of the LROC instrument. There are no oceans on the moon, so it doesn't make sense to describe any of these altitudes as above or below sea level, but green areas represent something of an average lunar height. Lower areas are shaded blue, with higher altitudes in red. The lowest areas are about 15,420 feet below the average height, with the highest being about 30,840 feet above average. Mt. Everest, for comparison, is 29,029 feet tall. Credit: NASA/Goddard/Arizona State University
Several hundred WAC images were combined to form this model. It is a subset of an almost global model, which is currently under construction and which will consist of more than 10,000 WAC images. This particular terrain model was produced using a software system that was originally developed by the German Aerospace Center for the High Resolution Stereo Camera (HRSC) on the European Mars Express Mission.
Related Links
› Arizona State University's Web site for the LRO Camera
› More images from Arizona State University's LROC site
For more information visit http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20100120-orientale.html
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