The document discusses the history and components of the Global Positioning System (GPS). It describes how the US Department of Defense launched initial GPS satellites from 1978-1984 and how the full system of 21+3 satellites was completed by 1993. The GPS system uses satellites in medium earth and geocentric orbits to provide positioning services with accuracy of within 10 meters globally for both military and civilian uses, such as navigation, construction, and vehicle tracking.

1. Global Position SystemBy HengYu Lou

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3. HistoryDOD (U.S. Department of Defense)1978 to 1979 four GPS satellite1979 to 1984 seven GPS satellite named BLOCK I1993 21+3 GPS satellite is in space The Global Position System is finally finish

4. SystemGEO (Geocentric Orbit) 22,369 mileMEO (Medium Earth Orbit) between GEO and LEOLEO (Low Earth Orbit) 1,243 mileGPS 12,552 mile21+3 1 Maine station4 Ground Antenna6 Monitor Station

5. UsageConstructionAlarm systemNavigationWeaponCarBoatAirplane

6. militaryGPS was build for militarySPS (standard positioning service)PPS (Precise Positioning Service)SA (Selective Availability) 100 meterAfter 2000 cancel SA to 10 meter

7. ProNo weather effectCover 98 percent of globeThree dimensions accuracyFastMany usageMoveable

8. Con24 satellites not enoughNeed at least three to workNot workable underground like tunnel

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