User`s guide

Appendix
Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05
212
Tropospheric correction
The correction applied to the measurement to account for tropospheric delay. This value
is normally obtained from the modified Hopfield model, the parameters of which are
broadcast by the satellites.
True Anomaly
The angular distance, measured in the orbital plane from the earth's center (occupied
focus) from the perigee to the current location of the satellite (orbital body).
Universal Time
Local solar mean time at Greenwich Meridian. Some commonly used versions of
universal time follow:
UTO - Universal time as deduced directly from observations of stars and the
fixed numerical relationship between universal and sidereal time (3 minutes,
56.555 seconds per day).
UT1 - UTO corrected for polar motion.
UT2 -UTO corrected for seasonal variations in the earth's rotational rate.
UTC - Universal time coordinated; uniform atomic time system kept very close to
UT2 by offsets. Maintained by the U.S. Naval Observatory (USNO).
GPS time is directly related to UTC by the following:
UTC - GPS = UTC offset (13 seconds in 2003)
User Range Accuracy (URA)
The contribution to the range measurement error from an individual error source
(apparent clock and ephemeris prediction accuracies) converted into range units,
assuming that the error source is uncorrelated with all other error sources.
UTM
Universal transverse mercator conformal map projection. A special case of the transverse
mercator projection. Abbreviated as the UTM grid, it consists of 60 north-south zones,
each six degrees wide in longitude.
VDOP
Vertical dilution of precision. See Dilution of Precision.
Vernal Equinox
One of two dates per year when the equator and ecliptic intersect along the line between
the earth and sun. On these days, the day and night are each 12 hours long everywhere
on earth, hence the term equinox, or "equal nights". The vernal equinox corresponds to
the spring equinox in the Northern Hemisphere.
Warm Start
Typical time a GPS receiver requires to develop a fix after application of power, given
that the receiver has stored time, position, and almanac data.