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GSR2600
Appendix B
Glossary
Global Positioning System (GPS) -
Full name NAVSTAR
Global Positioning System, a space-based radio positioning
system which provides suitably equipped users with accurate
position, velocity and time data. When fully operational, GPS
will provide this data free of direct user charge worldwide,
continuously, and under all weather conditions. The GPS
constellation will consist of 24 orbiting satellites, four equally
spaced around each of six different orbiter planes. The system is
being developed by the Department of Defense under U.S. Air
Force management. GPS consists of the following:
•
Space segment (up to 24 NAVSTAR satellites in 6 different
orbits)
•
Control segment (5 monitor stations, 1 master control
station and 3 upload stations)
•
User segment (GPS receivers)
NAVSTAR satellites carry extremely accurate atomic clocks
and broadcast coherent simultaneous signals.
GPS Time -
The time system upon which GPS is based. GPS
time is an atomic time system and is related to International
Atomic Time in the following manner:
International Atomic Time (IAT) = GPS + 19.000 sec. Note: IAT
and Universal Time Coordinated (UTC) are closely related. The
difference is that UTC has leap seconds put in to adjust for
changes in the earth’s rotation. see Universal Time Coordinated
(UTC).
GPS Week -
GPS time started at Saturday/Sunday midnight,
January 6, 1980. The GPS week is the number of whole weeks
since GPS time zero.
Greenwich Mean Time (GMT) -
Time based on the Greenwich
meridian as reference. In distinction from time based on a local
meridian or the meridian of a time zone.
HI -
Height of Instrument
IODE -
Issue of Data (Ephemeris)
Iono-free Carrier Phase Observation -
A linear combination of
L1 and L2 carrier phase measurements which provides an
estimate of the carrier phase observation on one frequency with
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