Differential GPS is an enhancement and a method of increasing the accuracy of positions derived from GPS receivers. There are 3 main components in performing this system which are;
Ä Base station.
Ä Rover station.
Ä Radio link.
It uses a network of fixed ground based reference station to broadcast the difference between the positions indicated by the satellite system and the known fixed position. This station broadcast the difference between the measured satellite pseudo range and actual (internally computed) pseudo range, and receiver station may correct their pseudo range by the same amount. This correction will be sent by radio link.With DGPS, position accuracy is improved, going from 30 metres to better than 10 metres. This system requires at least 2 GPS instruments (receivers & antennas) transmitting positions from at least 4 GPS satellites. 1 GPS instrument set up on a base station with known position and the other 1 set up on a static or dynamic rover station with unknown position.
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