SC872-A
Product User Guide
Glossary and Acronyms
1VV0301202 Rev. 6
Page 49 of 53
2018-12-21
16 GLOSSARY AND ACRONYMS
AGPS:
Assisted (or Aided) GPS
AGPS provides ephemeris data to the receiver to allow faster
cold start
times than would be possible
using only broadcast data.
This extended ephemeris data could be either server-generated or locally-generated.
See Local Ephemeris prediction data and Server-based Ephemeris prediction data
Almanac:
A reduced-precision set of orbital parameters for the entire GPS constellation that allows calculation of
approximate satellite positions and velocities. The almanac may be used by a receiver to determine
satellite visibility as an aid during acquisition of satellite signals. The almanac is updated weekly by the
Master Control Station. See
Ephemeris
.
BeiDou (BDS) - formerly COMPASS
:
The Chinese
GNSS
, currently being expanded towards full operational capability.
Cold Start:
A cold start occurs when a receiver begins operation with unknown position, time, and ephemeris data,
typically when it is powered up or restarted after a period on inactivity. Almanac information may be used
to identify previously visible satellites and their approximate positions. See
Restart
.
Cold Start Acquisition Sensitivity:
The lowest signal level at which a GNSS receiver is able to reliably acquire satellite signals and calculate
a navigation solution from a Cold Start. Cold start acquisition sensitivity is limited by the data decoding
threshold of the satellite messages.
EGNOS:
European Geostationary Navigation Overlay Service
The European
SBAS
system.
Ephemeris
(plural ephemerides):
A set of precise orbital parameters that is used by a GNSS receiver to calculate satellite position and
velocity. The satellite position is then used to calculate the navigation solution. Ephemeris data is updated
frequently (normally every 2 hours for GPS) to maintain the accuracy of the position calculation. See
Almanac
.
ESD:
Electro-Static Discharge
Large, momentary, unwanted electrical currents that can cause damage to electronic equipment.
GAGAN:
The Indian
SBAS
system.
Galileo:
The European
GNSS
currently being built by the European Union (EU) and European Space Agency
(ESA).
GDOP:
Geometric Dilution of Precision
A factor used to describe the effect of satellite geometry on the accuracy of the time and position solution
of a
GNSS
receiver. A lower value of GDOP indicates a smaller error in the solution. Related factors
include PDOP (position), HDOP (horizontal), VDOP (vertical) and TDOP (time).
GLONASS
: ГЛОбальная НАвигационная Спутниковая Система
GLObal'naya NAvigatsionnaya Sputnikovaya Sistema
(Global Navigation Satellite System)
The Russian
GNSS,
which is operated by the Russian Aerospace Defense Forces
