TV Antenna User Manual

Acutime 2000 Synchronization Kit User Guide Glossary-5
Glossary
elevation mask
angle
A measure of the minimum elevation angle, above the
horizon, above which a GPS satellite must be located before
the signals from the satellite will be used to compute a GPS
location solution. Satellites below the elevation angle are
considered unusable. The elevation mask angle is used to
prevent the GPS receiver from computing position solutions
using satellites which are likely to be obscured by buildings
or mountains.
ellipsoid In geodesy, unless otherwise specified, a mathematical
figure formed by revolving an ellipse about its minor axis. It
is often used interchangeably with spheroid. Two quantities
define an ellipsoid; these are usually given as the length of
the semi-major axis, a, and the flattening, f = (a - b)/a, where
b is the length of the semi-minor axis.
ephemeris A set of parameters that describe the satellite orbit very
accurately. It is used by the receiver to compute the position
of the satellite. This information is broadcast by the
satellites.
epoch Measurement interval or data frequency, as in making
observations every 15 seconds. Loading data using 30-
second epochs means loading every other measurement.
firmware A set of software computer/processor instructions that are
permanently or semi-permanently resident in read-only
memory.
frequency The number of vibrations per second of an audio or radio
signal. Measured in hertz (Hz), kilohertz (kHz), or
megahertz (MHz).
GPS frequencies are:
L1 = 1575.42 MHz
L2 = 1227.60 MHz