GPS for Dummies.pdf - Engineering Surveyor

Chapter 2: Dissecting Maps45The highest resolution commercial satelliteimagery available is .61 meters, from Digital-Globe’s QuickBird satellite (www.digitalglobe.com).By 2006, commercial satellites are expected tohave resolution as high as 0.25 meters. That’spretty close to the resolution of spy satellites,I spywhich are thought to have a resolution of 0.1meters. (The best spy satellites can reputedlydiscern objects about the size of a baseball.Despite what you see in the movies, licenseplate numbers are too small to be read by spysatellites, especially considering they don’t faceup toward space.)Resolution defines the smallest object a satellite can distinguish. A satellitewith one-meter resolution can distinguish objects down to a meter (a littleunder 40 inches) in size.Figure 2-16 is a ten-meter resolution SPOT satellite data of Mt. Bachelor, fromDeLorme’s Spot 10 collection of satellite data. (SPOT, which stands for SystemePour l’observation de la Terre, is a French commercial satellite program thatstarted in 1986.)Figure 2-16:A ten-meterresolutionsatelliteimage.Although most free satellite imagery doesn’t come close to the resolution ofsome commercial sources, the government is relying increasingly on privatecompanies to acquire data. I expect that government sources eventually willrelease high-resolution, color imagery to the public.