Differential GPS

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Method of Differential Correction


The reference ground station(s) at known locations receive NAVSTAR signals.

Knowing position of the station, the pseudo-range to each SV is calculated based on the almanac

The measured pseudorange, PRM(t), is determined

The pseudorange correction is calculated as the difference

The pseudorange correction, PRC(t), and the Range Rate Correction RRC(t) are sent from the reference ground station


GPS – How it works


Constellation of more than 24 satellites
Known positions (at any time)
Each continuously transmits time and position data
Two frequencies (L1-1575.42MHz and L2-1227.6MHz)
Each orbits twice per day

Ground receiver (Your GPS receiver)
Calculates Position and Time
Times signal and calculates distance to each satellite received
Triangulates Latitude and Longitude
Calculates time
Must see a minimum of 4 satellites