NorthStar MX500 Operator's & Installation Manual page 271

Glossary
ROOT MEAN SQUARED (RMS)
ROUTE
RTCM
S/A
SATELLITE HEALTH
SATELLITE SIGNAL
SELECTIVE AVAILABILITY (S/A)
SEMIMINOR AXIS
SENSOR
Version 3.0
A statistical measure of probability, stating that an expected event
will happen 68% of the time. In terms of position update accuracy,
68 position updates out of 100 will be accurate to within specified
system accuracy.
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.
Radio Technical Commission for Maritime Services.
See SELECTIVE AVAILABILITY
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.
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.
A system whereby the accuracy of GPS is reduced. S/A is con-
trolled by the U.S. Department of Defense.
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.
A device that detects a change in a physical stimulus and turns it
into a signal that can be measured.
Operator's Manual
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