NAVIOR-24S
™
Appendix G
Glossary
223
NAVIOR-24S ™
Revision
V1.00 20.05.2008
position measurements.
Doppler shift
The apparent change in frequency of a received signal due to the rate of
change of the range between the transmitter and receiver.
earth-centered
earth-fixed
Cartesian coordinate system where the X direction is the intersection of
the prime meridian (Greenwich) with the equator. The vectors rotate
with the earth. Z is the direction of the spin axis
elevation angle
The angle between the line of sight vector and the horizontal plane.
elevation mask angle
A measure of the minimum elevation angle, above the horizon, above
which a GPS/GLONASS satellite must be located before the signals
from the satellite will be used to compute a GPS/GLONASS location
solution. Satellites below the elevation angle are considered unusable.
The elevation mask angle is used to prevent the GPS/GLONASS
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 semimajor axis, a, and the
flattening, f = (a - b)/a, where b is the length of the semiminor 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
GLONASS frequencies are L1 = 1598,0625…1605,375 MHz
GDOP
Geometric Dilution of Precision. GDOP describes how much an
uncertainty in pseudo-range and time affects the uncertainty in a
position solution. GDOP depends on where the satellites are relative to
the GPS receiver and on GPS clock offsets
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. This
