Leica Geosystems GPS Basics - Manual (Page 55)

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GPS Basics -1.0.0en Glossary
P-code
The Precise GPS code - a very long
(about 10 14 bit) sequence of pseudoran-
dom binary biphase modulations on the
GPS carrier at a chipping rate of 10.23
MHz which does not repeat itself for
about 267 days. Each one-week
segment of the P-code is unique to one
GPS satellite, and is reset each week.
Access to the P-code will be restricted by
the U.S. Government to authorized users
only.
PDOP
Position dilution of precision.
see Dilution of Precision
Phase observable
See Reconstructed Carrier Phase
Point Positioning
The independent reduction of observa-
tions made by a particular receiver using
the pseudorange information broadcast
from the satellites.
Post processing
The process of computing positions in
non-real-time, using data previously
collected by GPS receivers.
Precise positioning service (PPS)
The highest level of point positioning
accuracy provided by GPS. It is based
on the dual-frequency P - code.
Propagation delay
See Atmospheric propagation delay,
and Ionospheric delay
Pseudolite
The ground-based differential GPS
station which transmits a signal with a
structure similar to that of an actual GPS
satellite.
Pseudorandom noise (PRN) code
Any group of binary sequences that
appear to be randomly distributed like
noise, but which can be exactly distrib-
uted. The most important property of
PRN codes is that the sequence has a
minimum autocorrelation value, except
at zero lag.
Pseudorange
A measure of the apparent signal
propagation time from the satellite to the
receiver antenna, scaled into distance by
the speed of light. The apparent propa-
gation time is the difference between the
time of signal reception (measured in
the receiver time frame) and the time of
emission (measured in the satellite time
frame). Pseudorange differs from the
actual range by the influence of satellite
and user clock.
Range
Term used in Navigation for the length of
the trajectory between two points. The
trajectory is normally the great circle or
the rhumb line.