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Glossary
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FirstGPS Starter Kit User Guide
Dilution of precision
(DOP)
A description of the purely geometrical contribution to the
uncertainty in a position fix, given by the expression:
DOP = SQRT TRACE (A)
where: A = (G
T
G)
-1
of G, the geometry matrix,
corresponding to the measurement connection matrix for
the instantaneous position solution (dependent on
satellite-receiver geometry)
1
.
The DOP factor depends on the parameters of the
position-fix solution. Standard terms for GPS application
are:
Geometric DOP – Three position coordinates plus
clock offset in the solution.
Position DOP – Three coordinates.
Horizontal DOP – Two horizontal coordinates.
Vertical DOP – Height only.
Time DOP – Clock offset only.
1
Refer to Global Positioning System: Theory and
Applications, Volume I. Parkinson, Spilker, Axelrad, and
Enge (1996), p. 413.
DSP Digital Signal Processor.
DOP Dilution of precision.
Earth-Centered-Earth-
Fixed coordinates
The Cartesian coordinate system in which 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.
ECEF See Earth-Centered-Earth-Fixed coordinates.
EMI Electromagnetic interference.