User`s guide

Appendix
Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05
203
Flattening
A parameter used to define the shape of an ellipsoid.
f = (a - b)/a = 1 - (1 - e2)1/2, where
a = semi-major axis
b = semi-minor axis
e = eccentricity
Frequency Band
A range of frequencies in a particular region of the electromagnetic spectrum.
Frequency Spectrum
The distribution of amplitudes as a function of frequency of the constituent waves in a
signal.
Fundamental Frequency
The fundamental frequency used in GPS is 10.23 MHz. The carrier frequencies L1 and
L2 are integer multiples of this fundamental frequency.
L1 = 154F = 1575.42 MHz
L2 = 120F = 1227.60 MHz
GDOP
Geometric dilution of precision. See Dilution of Precision.
GDOP
2
= PDOP
2
+ TDOP
2
Geocenter
The center of mass of the earth.
Geodetic Datum
A mathematical model designed to best fit part or all of the geoid. It is defined by an
ellipsoid and the relationship between the ellipsoid and a point on the topographic surface
established as the origin of datum. The relationship can be defined by six quantities
generally (but not necessarily) the geodetic latitude, longitude, and height of the origin,
the two components of the deflection of the vertical at the origin, and the geodetic
azimuth of a line from the origin to some other point.
Geoid
The particular equi-potential surface which coincides with mean sea level, and which may
be imagined to extend through the continents. This surface is perpendicular to the force
of gravity at all points.
Geoid Height
The height above the geoid is often called elevation above mean sea level.
GPS
Global Positioning System, consisting of the space segment (up to 24 NAVSTAR
satellites in six different orbital planes), the control segment (five monitor stations, one
master control station and three uplink stations), and the user segment (GPS receivers).
NAVSTAR satellites carry extremely accurate atomic clocks and broadcast coherent
simultaneous signals.