ashtech DG14, Reference Manual

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342 DG14 and DG16 Board & Sensor Reference Manual
Antenna
A variety of GPS antennas ranging
from simpler microstrip devices to
complex choke ring antennas that
mitigate the effects of multipath
scattering.
Anti-Spoofing (AS)
The process of encrypting the P-Code
modulation sequence so the code
cannot be replicated by hostile forces.
When encrypted, the P-Code is
referred to as the Y-Code.
ASCII
American Standard Code for
Information Interchange. A set of
characters (letters, numbers, symbols)
used to display and transfer digital data
in human-readable format.
Atomic clock
A clock whose frequency is maintained
using electromagnetic waves that are
emitted or absorbed in the transition of
atomic particles between energy
states. The frequency of an atomic
transition is very precise, resulting in
very stable clocks. A cesium clock has
an error of about one second in one
million years. For redundancy
purposes, GPS satellites carry multiple
atomic clocks. GPS satellites have
used rubidium clocks as well as cesium
clocks. The GPS Master Control
Station uses cesium clocks and a
hydrogen master clock.
Argument of latitude
The sum of the true anomaly and the
argument of perigee.
Argument of perigee
The angle or arc from the ascending
node to the closest approach of the
orbiting body to the focus or perigee, as
measured at the focus of an elliptical
orbit, in the orbital plane in the direction
of motion of the orbiting body.
Ascending node
The point at which an object’s orbit
crosses the reference plane (e.g.,
equatorial plane) from south to north.
Azimuth
A horizontal direction expressed as the
angular distance between a fixed
direction and the direction of the object.
AZM
See Azimuth
Bandwidth
A measure of the information-carrying
capacity of a signal expressed as the
width of the spectrum of that signal
(frequency domain representation) in
Hertz.
Baseline
The measured distance between two
receivers or two antennas
Bias
See Integer bias terms
BIN
Binary Index (file)
C/A
Coarse Acquisition
C/A code
A sequence of 1023 bits (0 or 1) that
repeats every millisecond. Each satellite
broadcasts a unique 1023-bit sequence
that allows a receiver to distinguish