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GSR2600
Appendix B
Glossary
Static Surveying -
A method of GPS surveying that involves
simultaneous observations between stationary receivers. Post-
processing computes the vector between points.
SV -
Space Vehicle. In GPS, the space vehicle refers to satellites.
Time-To-First-Fix (TTFF) -
The actual time required by a GPS
receiver to achieve a position solution. This specification will
vary with the operating state of the receiver, the length of time
since the last position fix, the location of the last fix, and the
specific receiver design.
Undulation -
The distance of the geoid above (positive) or
below (negative) the mathematical reference ellipsoid
(spheroid). Also known as geoidal separation, geoidal
undulation, and geoidal height.
Universal Time Coordinated (UTC) -
Time as maintained by
the U.S. Naval Observatory. Because of variations in the Earth's
rotation, UTC is sometimes adjusted by an integer second. The
accumulation of these adjustments compared to GPS time,
which runs continuously, has resulted in an 13 second offset
between GPS time and UTC at the start of 1999. After accounting
for leap seconds and using adjustments contained in the
navigation message, GPS time can be related to UTC within 20
nanoseconds or better.
WGS84 -
World Geodetic System 1984 is an ellipsoid designed
to fit the shape of the entire Earth as well as possible. It is often
used as a reference on a worldwide basis, while other ellipsoids
are used locally to provide a better fit to the Earth in a local
region. GPS uses the center of the WGS84 ellipsoid as the center
of the GPS ECEF reference frame.
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