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1、Global Position System,Basic components and theory of the GPS,GPS components and aircraft equipment Composition of satellite constellation Satellites required for 2D and 3D navigation Basic concept of satellite ranging Accuracy of GPS,GPS,Started by the Department of Defense in 1973 The first satell
2、ite launched in 1978 By 1993 the full 24 satellite system was in place,Who operates this system?,The 2nd Space Operation Squadron of the 50th Space Wing at Falcon Air force Base, Colo. Why do we get to use this system? Cost to develop it,GPS,This system was developed to overcome the limitation of ex
3、isting systems. Weather Terrain Overlap of signal Accuracy Cost,Global Position Satellite,There are 24 satellites orbiting the earth every 12 hours.,Each satellite is launched by a Delta Rocket.,Global Position Satellite,Weight: 2050 lb. Power plant: solar panels generating 1100 watts Uses two L ban
4、d frequencies Dimensions: 5wide, 17.5 long (length includes solar arrays) Tilted at 55 Orbit altitude: 10,900nm. Design life: 7.5 years,Global Position Satellite,Master Control Station (operated at Schriever AFB, Colo.) is responsible for monitoring and controlling the GPS satellite constellation Th
5、ere are five monitoring stations and four ground antennas located around the world. MCS uses s-band to talk to the satellites.,Receivers,Types and Features Basic and advancedBasic,Receivers,Advanced The major difference: RAIM Can be certified for IFR approaches The functions are endless,Database,Dat
6、abase (types) Self programming Removable card Computer updating,How satellites work,The group of radio frequencies extend from 390 MHz to 1550 MHz. The GPS carrier frequencies (1227.6 MHz and 1575.42 MHz) are in the L-band,How satellites work,Your GPS measures the distance from each satellite that i
7、t receives.,How satellites work,If you know you are 625 miles from Boise,you could be anywhere on this circle.,If you know you are 625 miles from Boise and 690 miles from Minneapolis, then you know you must be at one of two points.,With three known points, you can determine that your exact location
8、is somewhere near Denver, Colorado!,How GPS works,Since we are using satellites, we end up with a 3D pin point With more then 3 satellites we can find our altitude,GPS Accuracy Errors,In the beginning military placed an error of 30 to 100 meters in the satellite SV Clock Errors GPS needs accurate ti
9、me to ensure accurate latitude, longitude, altitude, and groundspeed,GPS Accuracy Errors,Water Vapor slows the speed of the signals Earths ionosphere slows the speed of signal Some receivers may incorporate a few feet of uncertainty into every measurement, due to the rounding off mathematical operat
10、ions,GPS Accuracy Errors,Over the north pole the satellites are very low on the horizon. The result is a very poor vertical indication.,GPS Accuracy Errors,Poor visibility can be caused by nature or man made objects.,GPS Accuracy Errors,All of these inaccuracies, even if taken together, will affect
11、the accuracy of position calculations by no more than 25 to 50 meters Accuracy can be boosted using a technique called Differential GPS, a receiver on the ground measures the distance to the satellites, and calculates corrections to match the GPS,In Conclusion,GPS components and aircraft equipment Composition of satellite constellation Satellites required for 2D and 3D navigation Basic concept of satellite ranging Accuracy of GPS,The End,
