CONS 127 Lecture Notes - Lecture 5: Wi-Fi, Global Positioning System, Pseudorange
15 Sep 2017
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Document Summary
What is gps: global positioning system, full name: navstar gps, launched by usa in 1978, broader term: global navigation satellite systems (gnss, gnss = gps (usa) + glonass (russia) + galileo (european union) History: 70s as concept, working system in 1995 (24 satellites, affordable 96-99, 2000 non military asset, commitment that system always operating for civilians. How do they work: three system segments, space segment, we need 3 satellites minimum to find location, minimum of 24 satellites on 6 orbits. How does gps work out where you are: where 3 unique points of distance intersect, calculation location, same but in 3 dimention. Differential gnns: method to increase measurement accuracy, requires additional receiver that stays stationary, if errors are the same on both devices, you can cancel the errors out, accuracy can go down from 10m-10cm. A-gps: assisted gps, wi-fi or phone network tells phone where satellites are, quicker.
