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Operator's Manual
RMS
See ROOT MEAN SQUARED.
ROOT MEAN SQUARED (RMS)
Glossary
212
A statistical measure ofprobability, stating that an expected event
will happen 68% ofthe time: In terms ofposition update accuracy,
68 position updates out of 100 will be accurate to within specified
system accuracy.
ROUTE
A route is a sequential list of waypoints describing a planned voy-
age. The active route is the route used for the actual navigation of
the vessel.
RTCM
Radio Technical Commission for Maritime Services.
S/A
SeeSELECTIVE AVAlLABlLITY
SATELLITE HEALTII
Go or no-go message for each satellite included in the almanac
data. The message states whether or not the measurements from
those particular satellites can be relied upon for accurate results.
SATELLITE SIGNAL
Transmitted electromagnetic energy from a GPS satellite whose
time of arrival is measured by the navigator to calculate the posi-
tion of the navigator antenna.
SELECITVE AVAlLABlLITY (SI A)
A system whereby the accuracy of GPS is reduced. SI A is con-
trolled by the U.S. Department of Defense.
SEMIMINOR AXIS
The distance from the center of the earth's ellipse to the ellipse
surface as measured along the polar axis. It is identified symboli-
cally with the letter B, and it varies according to the reference da-
tum used for position coordinates.
SENSOR
A device that detects a change ill a physical stimulus and turns it
into a signal that can be measured.
Version 1.5
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