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Glossary-4 Acutime 2000 Synchronization Kit User Guide
Glossary
differential
relative
positioning
Determination of relative coordinates of two or more
receivers which are simultaneously tracking the same
satellites. Static differential GPS involves determining
baseline vectors between pairs of receivers. Also see
differential GPS.
dilution of
precision
A description of the purely geometrical contribution to the
uncertainty in a position fix, given by the expression DOP =
SQRT TRACE (A A) where A A is the design matrix for the
instantaneous position solution (dependent on satellite-
receiver geometry). The DOP factor depends on the
parameters of the position-fix solution. Standard terms for
the GPS application are:
GDOP – Geometric (three position coordinates plus clock
offset in the solution)
PDOP – Position (three coordinates)
HDOP – Horizontal (two horizontal coordinates)
VDOP – Vertical (height only)
TDOP – Time (clock offset only)
RDOP – Relative (normalized to 60 seconds)
DOP See dilution of precision.
Doppler shift The apparent change in frequency of a received signal due
to the rate of change of the range between the transmitter
and receiver.
earth-centered
earth-fixed
(ECEF)
Cartesian coordinate system where the X direction is the
intersection of the prime meridian (Greenwich) with the
equator. The vectors rotate with the earth. Z is the direction
of the spin axis.
elevation angle The angle between the line of sight vector and the horizontal
plane.