Trimble Outdoors AcutimeTM2000 Synchronization Kit, Part Number 45005-00-ENG manual Elevation mask

	Glossary
elevation mask	A measure of the minimum elevation angle, above the
angle	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

Acutime 2000 Synchronization Kit User Guide Glossary-5