National Geographic : 1995 Jun
Making the image TO GENERATE from satellite data a dramatic oblique view that looks three-dimensional, proj ect coordinator Richard Cleave led an international effort. He began with a high-resolution Landsat 5 image of the Holy Land in which each colored picture element, or pixel, cov ers a 30-by-30 -meter square. Technicians at Earth Satel lite Corporation in Rockville, Maryland, then combined the Landsat color data with gray scale data recorded by a French SPOT satellite. Among the most detailed satellite images available to the public, the SPOT scenes have ten meter pixels. In the new image (1) resolution was increased dramatically. Next John K. Hall of the Geo logical Survey of Israel pre pared a digital terrain model from detailed topographic maps. The model consists of elevations distributed on a 25 meter grid. It can be used to illustrate topographic informa tion in a variety of ways, from a color-coded contour map (2) to a mesh relief model (3). Computers at Technion Israel Institute of Technology in Haifa were used to merge the satellite data with the ele vation data. This created the effect of draping the image over a relief map. Software developed by Tech nion's Craig Gotsman and Gennady Agranov then let Cleave interact with the data base, simulating flight over the landscape and viewing it from any angle or height like an aerial photographer. He could also exaggerate relief, a tech nique for emphasizing detail. Inthis way he selected the scenes for this article, such as the one of Haifa blanketing the slopes of Mount Carmel (4).