Furuno GD-280, Operator'S Manual

Page: 162 / 280

10-6
10.2 DGPS Setting (set with built-in DGPS receiver)
10.2.1 How DGPS works
Position accuracy for users of GPS is about 10 meters. With Differential GPS (DGPS), however,
differential corrections can improve position accuracy to better than 5 meters.
Differential GPS is based upon accurate knowledge of the accurate geographical location of a
reference station which is used to compute corrections to GPS parameters, error sources and
resultant positions. These differential corrections are transmitted to GPS users, who apply the
corrections to their received GPS signals or computer position.
The DGPS reference stations are fixed at a geodetically surveyed position. The reference station
tracks all satellites in view, downloads ephemeric data from them, and computes corrections
based on its measurement and geodetic position. These corrections are then broadcast to GPS
users by radio beacons (transmitters) to improve their position solution.
The radio beacons broadcast in the frequency range of 283.5-325.0 kHz and have a transmitting
range from 40 nm to 300 nm depending on radio beacon.
Reference
Station
GPS Signal
Corrected Data
DGPS Beacon Receiver
GPS Receiver