The Dream of a Mapmaker
July 31, 2001
Imagine the work it would have taken a hundred years ago to generate this map of the eastern flank of the Andes in Argentina near San Martin de Los Andes with the detail and accuracy of the image shown above. Not an artist's or cartographer's rendering, this colorful image was created entirely from data collected by the Shuttle Radar Topography Mission (SRTM) flown in February, 2000. Two visualization methods were combined to produce this image: shading and color coding of topographic height. The shade image was derived by computing topographic slope in the north-south direction. Northern slopes appear bright and southern slopes appear dark, as would be the case at noon at this latitude in the southern hemisphere. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow, red and magenta to white at the highest elevations. The result is a colorful and easy to grasp map of this part of the world, showing eroded peaks on the left, smoothe lava plateaus and signs of recent volcanic activity with a dimpled cone and surrounding flow field in the center. North is to the top of the image which covers 57.6 x 40.5 kilometers on the surface. SRTM mapped most of the Earth's land surface in this way, promising a global topographic map of unprecendented consistency and accuracy.