222 G12 OEM Board & Sensor Reference Manual
of the frequency offset between the
satellite and receiver reference
oscillators.
Real-time
Refers to immediate, GPS data
collection, processing and position
determination (usually) within a
receiver's firmware after the fact with a
computer in an office environment.
Reference Network
A series of monuments or reference
points with accurately measured
vectors/distances that is used as a
reference basis for cadastral and other
types of survey.
Reference station
A point (site) where crustal stability, or
tidal current constants, have been
determined through accurate
observations, and which is then used
as a standard for the comparison of
simultaneous observations at one or
more subordinate stations. Certain of
these are known as Continuous
Operating Reference Stations (CORS),
and transmit reference data on a 24-
hour basis.
Relative positioning
The process of determining the relative
difference in position between two
points with greater precision than that
to which the position of a single point
can be determined. Here, a receiver
(antenna) is placed over each point and
measurements are made by observing
the same satellite at the same time.
This technique allows cancellation
(during computations) of all errors
which are common to both observers,
such as satellite clock errors,
propagation delays, etc. See also
Translocation and Differential
Navigation.
RF
Radio Frequency
RFI
Radio Frequency Interference
RINEX
The R
eceiver-INdependent EXchange
format for GPS data, which includes
provisions for pseudorange, carrier-
phase, and Doppler observations.
RMS
Root Mean Square. A statistical measure
of the scatter of computed positions
about a "best fit" position solution. RMS
can be applied to any random variable.
RTCM
Radio Technical Commission for
Maritime Services
P.O. Box 19087
Washington, DC. 20036-9087
RTCM SC-104 Format
A standard format used in the
transmission of differential corrections.
Selective Availability (SA)
The process whereby DOD dithers the
satellite clock and/or broadcasts
erroneous orbital ephemeris data to
create a pseudorange error
SEP
See Spherical Error Probable
Sidereal day
Time between two successive upper
transits of the vernal equinox.
Sidereal time
The hour angle of the vernal equinox.
G12RevD.book Page 222 Tuesday, April 2, 2002 4:33 PM
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