Abbreviations - Nokia 9000 Quick Manual

1. ABBREVIATIONS

This section defines some technical terms and abbreviations used in the field of GPS technology.
Almanac
C/A code
DGPS
Differential Relative
Positioning
DOP (Dilution of
precision)
Epoch
GDOP
Geoidal separation
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A reduced-precision subset of the ephemeris parameters. Used by the
receiver to compute the elevation angle, azimuth angle and estimated
Doppler of the satellites. Each satellite broadcasts the almanac for all the
satellites in the system
The Coarse/Acquisition code. This is the civilian code made available by
the Department of Defense (DOD). It is subject to selective availability
(SA). Users can reduce the effects of SA using differential GPS.
Differential GPS is a procedure for correcting GPS solutions to achieve
improved position accuracy. Differential GPS provides 2 to 5 meter
position accuracy. Differential accuracy is obtained by applying
corrections determined by the stationary Differential GPS Reference
Station to the GPS data collected by the RPU unit on board the vehicle.
Determination of the 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.
A description of the purely geometrical contribution to the uncertainly in a
position fix, given by the expression DOP = SQRT TRACE (AA) where
AA is the design matrix for the instantaneous position solution
(dependent on satellite-receiver geometry). 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)
Measurement interval or data frequency, as in making observations every
15 seconds. Loading data using 30-second epochs means loading every
other measurement
Geometric Dilution of Precision. GDOP describes how much an
uncertainly in pseudo-range and time affects the uncertainty in a position
solution. GDOP depends on where the satellites are relative to the GPS
receiver and on the GPS clock offsets.
Geoidal separation is the difference between the WGS-84 earth ellipsoid
and mean-sea-level
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