Leica apMK12 Operation & Installation Manual page 209

Operation & Installation Manual
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S/A
See SELECTIVE AVAILABILITY
SATELLITE HEALTH
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.
SELECTIVE AVAILABILITY (S/A)
A system whereby the accuracy of GPS is reduced. S/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 in a physical stimulus and turns it
into a signal that can be measured.
SET AND DRIFT
The direction and the speed of the water over ground (current).
SIGNAL-TO-NOISE RATIO (S/N)
Quantitative relationship between the useful and non-useful part of
the received satellite signal. A high S/N indicates a good receiving
condition.
S/N
See SIGNAL-TO-NOISE RATIO
SOFTWARE
Values programmed and preloaded into memory. The values rep-
resent a permanent set of instructions for running the automatic
Glossary
Version 1.5
8/13/01, 11:08 AM