Section 13 - Glossary - NorthStar 8700 Technical Reference Manual

Section 13 - Glossary

Section 13 - Glossary
Almanac The compilation of satellite identification and orbital data used by a GPS
receiver.
Ephemeris data A uniform measure of data defined by the orbital motion of the planets.
The data is used to calculate exact satellite positions, continually updated
and derived from information relayed to the sensor in each satellite's data
stream.
Host The customer system receiving position data from the 8700/8800
series/8900 series.
Selective Availability The intentional degrading by the U.S. Department of Defense of satellite
(SA) signals tracked and measured by GPS receivers to determine position,
time, and velocity. SA limits civilian GPS accuracy to about 100 meters,
and velocity accuracy to about one to two knots.
Sentence A group of data in one of several formats defined by the National Marine
Electronics Association (NMEA). For standard applications, the Northstar
sensors are factory-programmed to output necessary sentences; for cus-
tom applications, the Northstar sensors can be programmed to output
any of several sentence types.
Sferics count Sferics count is the number of noise impulses that were blanked in the
previous 10-second interval. It's increased by poor weather conditions
and lightning.
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