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Rev. D 3 — Basic Navigation
3 — Basic Navigation3 — Basic Navigation
3 — Basic Navigation Page 27
For further information on operating in DGPS mode, refer to “Internal
Differential Beacon Receiver,” on page 74.
With DGPS active, you will often see position measurements accurate to
about 2-5 meters, speed measurements accurate to about 0.1 knot, and
Course-Over-Ground measurements accurate to about 0.5 degree. DGPS
corrections remove the errors caused by Selective Availability (SA) and
the atmosphere, and provide an accuracy exceeding that obtained by
military users of the GPS system. If the DGPS indicator is displayed, you
have this higher level of accuracy. For the
POSITION
and
STEERING
screens, the DGPS indicator is a large letter “D.” For the plotter screen,
the DGPS indicator is the symbol
DGPS
.
To display more information about signals received from the GPS satel-
lites, press the
SATS
menu key on the GPS position screen. A screen is
displayed showing the received Signal-to-Noise Ratio for each satellite,
and a map indicating where the satellites are currently located in the sky
(the 12-channel
GPS SATS
screen is shown on the next page). Satellites
are identified by their
PRN
number, a two-digit number assigned by the
U.S. government.
The center of the satellite map represents the center of the sky, and the
outer (or last) ring is the horizon. The view is looking down from above,
with East to your right and West to your left.
satellite status