1. Global Positioning System or GPS
... called GPS, and originally named NAVSTAR, is a satellite-based navigation system used for determining one's precise location and providing a highly accurate time reference almost anywhere on Earth. A GPS unit uses these "man-made stars" as reference points to calculate positions accurate ... by the United States Department of Defense and can be used by anybody for free. The cost of maintaining the system is approximately $400 million per year. The first of 24 satellites that form the current constellation of the Global Positioning System (Block II) was placed into orbit on February 14,...
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- Grade Level: High School