MAP GENERATED by the Mars Orbiter Laser Altimeter (MOLA), an instrument aboard NASA's Mars Global Surveyor, was created by bouncing an infrared laser off the surface of Mars and measuring the time it took for the pulses to return to calculate the distance to each point. The present map comprises 27 million elevation measurements gathered in 1998 and 1999. The data were assembled into a global grid with each point spaced 37 miles (60 kilometers) apart at the equator, and less elsewhere. Each elevation point is known with an accuracy of 42 feet (13 meters) in general, with large areas of the flat northern hemisphere known to better than six feet (two meters).
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