Garmin GBR 23 - Manual (Page 15)

13
GPS SIGNAL GPS SIGNAL
DGPS (CORRECTION) SIGNAL
SHIPBOARD GPS AND
DGPS RECEIVERS
CORRECTION
D
AT
A GPS RECEIVER
STATION AND
DGPS TRANSMITTER
Reference
After entering the beacon’s
operating frequency, set the
bit rate as indicated on the
Beacon Reference Card.
Beacon information is also
available from the other
sources listed on the card.
DGPS:
How It Works
DGPS: How It Works
Differential GPS (DGPS) is a technique used to
improve the accuracy of the Global Positioning System.
DGPS reduces the effects of atmospheric variations and
can improve position accuracy to better than 5 meters.
Figure 4: The DGPS System
A DGPS system consists of the following:
• DGPS Beacon Transmitter and GPS Receiver at
a known location
• Shipboard DGPS Beacon Receiver
• Shipboard GPS Receiver (DGPS capable)
• GPS Satellites
The DGPS Beacon Transmitter is placed at a known
location (i.e., the exact position of the site has been
previously determined). At the beacon transmitter site,
the GPS satellites are monitored using a GPS receiver.
This receiver is equipped to calculate corrections for each
satellite received. The correction is the difference between
the distance to the satellite (from the beacon site) as
measured by the GPS receiver, and the actual distance to
the satellite based on the known location of the beacon
site. These corrections are communicated to the users
GPS set through the DGPS Beacon Station and the
GBR 23. The users GPS set then uses the corrections to
remove errors from its measurements.
Select GARMIN DGPS
when using the GBR 23 with
GARMIN GPS units.
GBR 23 Manual.p65 5/23/00, 1:28 PM 13