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GSR2600
Appendix B
Glossary
Double-Difference Carrier Phase Ambiguity (or sometimes
double difference ambiguity or ambiguity, for short) -
Carrier
phase ambiguities which are differenced between receiver
channels and between the reference and remote receivers. They
are estimated when a double difference mechanism is used for
carrier phase positioning.
Earth-Centered-Earth-Fixed (ECEF) -
Earth-Centered-Earth-
Fixed. This is a coordinate-ordinate system which has the X-
coordinate in the earth's equatorial plane pointing to the
Greenwich prime meridian, the Z-axis pointing to the north
pole, and the Y-axis in the equatorial plane 90° from the X-axis
with an orientation which forms a right-handed XYZ system.
Elevation -
Height above a reference datum. The reference
datum may be an ellipsoid (ellipsoidal elevation), a geoid
(orthometric elevation), above mean-sea-level, or above a locally
defined reference plane.
Elevation mask angle -
An adjustable feature of GPS receivers
that specifies a satellite must be at least a specified number of
degrees above the horizon before the signals from the satellite
are to be used. Satellites at low elevation angles (five degrees or
less) have lower signal strengths and are prone to loss of lock
thus causing noisy solutions.
Ellipsoid -
A smooth mathematical surface which represents the
earth’s shape and very closely approximates the geoid. It is used
as a reference surface for geodetic surveys.
Ellipsoidal Height -
Height above a defined ellipsoid,
approximating the surface of the earth.
Ephemeris -
A set of satellite orbit parameters that is used by a
GPS receiver to calculate precise GPS satellite positions and
velocities. The ephemeris is used in the determination of the
navigation solution and is updated periodically by the satellite
to maintain the accuracy of GPS receivers. Available as
"broadcast ephemeris" or as post-processed "precise ephemeris."
Epoch -
Same as measurement time epoch. The local time at
which a GPSCard takes a measurement. For example,
15 seconds, 30 seconds.
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