Leica Geosystems GPS Basics - Manual (Page 48)

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GPS Basics -1.0.0en Glossary
Glossary
Almanac
Library of coarse satellite orbital data
used to calculate satellite position, rise
time, elevation, and azimuth.
Ambiguity
The unknown integer number of cycles
of the reconstructed carrier phase
contained in an unbroken set of mea-
surements from a single satellite pass
at a single receiver.
Anti-spoofing (A-S)
Encrypting the P-code (to form the Y-
code).
Atmospheric propagation delay
Time delay affecting satellite signals due
to tropospheric layers of the earth’s
atmosphere.
Azimuth
A horizontal angle measured clockwise
from a direction (such as North).
Bandwidth
A measure of the width of the spectrum
of a signal (frequency domain represen-
tation of a signal) expressed in Hertz.
Baseline
The length of the three-dimensional
vector between a pair of stations for
which simultaneous GPS data has been
collected and processed with differential
techniques.
Bearing
Term used in navigation to describe the
angle between a reference direction
(e.g., geographic north, magnetic north,
grid north) and the trajectory.
Beat frequency
Either of the two additional frequencies
obtained when signals of two frequen-
cies are mixed. The beat frequencies
are equal to the sum or difference of the
original frequencies, respectively.
Binary biphase modulation
Phase changes of either 0° or 180° (to
represent binary 0 or 1, respectively) on
a constant frequency carrier. These can
be modelled by
y = A cos (wt + p),
where the amplitude function A is a
sequence of +1 and -1 values (to
represent 0° and 180° phase changes
respectively). GPS signals are biphase
modulated.