NorthStar 961 Reference Manual page 58

Chapter 2 - Introducing the 961/962
Page 2-14
beacons, the transmitters are situated at various locations
along the U.S. coastline, Great Lakes, and major rivers.
What does all this mean? Using DGPS, the 962's
high-performance 12-channel GPS receiver and optional
two-channel internal differential receiver work together to
provide position accuracy of one to three meters 50 percent of
the time, and under four meters 95 percent of the time.
(Remember: one meter equals just over one yard!)
Differential corrections are invaluable when navigating in
such narrow or congested areas as ports and waterways, or
wherever you require extreme accuracy to locate a precise
area (retrieving lobster traps, returning to a favorite diving
spot, and so on.)
The 961/962 displays lat/lon coordinates to thousandths of
minutes (approximately six feet). When using a radar plotter or
paper plotter, DGPS corrections dramatically improve the
steadiness of your displayed plot line.
Monitoring GPS signal integrity
Besides providing highly accurate position data, DGPS
monitors the integrity of the received GPS signals. Integrity
monitoring helps detect a satellite problem in seconds,
compared to hours using non-differentiated GPS. How? The
integrity monitor tells the DGPS receiver to automatically stop
using any unhealthy satellites.
961/962 Operations and Reference Manual, Rev. A