 |
|
Glossary
National GPS web site specific terms
|
|
Active stations
|
A network of permanently recording, high quality, GPS receivers located
across GB. Raw GPS data is downloaded hourly from each station to the
National GPS Network web site.
|
|
Coordinate Converter
|
A utility to precisely convert ETRS89 coordinates to Ordnance Survey
National Grid coordinates (OSGB36®) and heights above mean sea level (MSL) (orthometric height) using the OSTN02® and OSGM02® models.
|
|
Ellipsoid
|
A 3-D geometric figure used to approximate the shape of the earth.
|
|
ETRS89
|
The European Terrestrial Reference System 1989, used as the standard
precise GPS coordinate system throughout Europe. In 2000, the difference
between the WGS84 and ETRS89 coordinates was about 25 cm, and increasing
by about 2.5 cm per year. ETRS89 has been officially adopted as a standard
coordinate system for precise GPS surveying by most national mapping
agencies in Europe.
|
|
Geoid
|
A model of the level surface which is closest to MSL over the oceans. This
surface is continued under the land and acts as the fundamental reference
surface for height measurement, as an approximation of MSL on land.
|
|
GPS
|
The Global Positioning System. An outdoor positioning technique which uses
a constellation of US Department of Defense satellites and a receiver to
determine position.
|
|
ODN
|
Ordnance Datum Newlyn is the national standard vertical reference
system for measuring height above MSL in GB. ODN is measured relative to a
value taken at Newlyn, Cornwall.
|
|
OSGB36 (National Grid)
|
The national standard coordinate system for topographic mapping, including
all Ordnance Survey mapping, and for geographically referencing many kinds
of information in relation to Ordnance Survey mapping.
|
|
OSGM02
|
Ordnance Survey National Geoid Model 2002. A gravimetric model used to convert from ETRS89 to orthometric heights.
|
|
OSTN02
|
Ordnance Survey National Grid Transformation 2002.
|
|
Passive stations
|
A network of stations across GB that have been precisely positioned with
GPS. ETRS89 coordinates, transformed OSGB36 coordinates and station
location information is available from the National GPS Network web site.
|
|
Transformation
|
A procedure to change from one coordinate system to another.
|
|
WGS84
|
The World Geodetic System 1984 coordinate system, used by GPS. WGS84
coordinates are usually expressed as latitude, longitude and ellipsoid
height.
|
|
General satellite navigation abbreviations
|
|
A-S
|
Anti-spoofing
|
|
C/A-code
|
coarse/acquisition-code
|
|
CEP
|
circular error probable
|
|
DGPS
|
differential GPS
|
|
DOP
|
dilution of precision
|
|
ECEF
|
Earth-centered-Earth-fixed
|
|
FOM
|
figure of merit
|
|
Galileo
|
European Global Navigation Satellite System under development
|
|
GDOP
|
geometric dilution of precision
|
|
GLONASS
|
Global Navigation satellite system
|
|
GMT
|
Greenwich Mean Time
|
|
GPS
|
Global Positioning System
|
|
HDOP
|
horizontal dilution of precision
|
|
HOW
|
hand over word
|
|
INS
|
Inertial Navigation System
|
|
L1
|
GPS primary frequency, 1575.42 MHz
|
|
L2
|
GPS secondary frequency, 1227.6 MHz
|
|
MSL
|
mean sea level
|
|
MTBF
|
mean time between failure
|
|
NMEA
|
National Marine Electronics Association
|
|
P-code
|
precise code
|
|
PDOP
|
position dilution of precision
|
|
PPM
|
parts per million
|
|
PPS
|
Precise Positioning Service
|
|
PRN
|
pseudo random noise
|
|
RF
|
radio frequency
|
|
RINEX
|
Receiver Independent Exchange Format
|
|
RMS
|
root mean square
|
|
RSS
|
root sum square
|
|
RTCA
|
Radio Technical Commission for Aeronautics
|
|
RTCM
|
Ratio Technical Commission for Maritime Services
|
|
RTK
|
Real-Time Kinematic
|
|
SA
|
Selective Availability
|
|
SEP
|
spherical error probable
|
|
SPS
|
Standard Positioning Service
|
|
TAI
|
International Atomic Time
|
|
TDOP
|
time dilution of precision
|
|
TTFF
|
time to first fix
|
|
UT
|
Universal Time
|
|
UTC
|
Universal Time Coordinated
|
|
VDOP
|
vertical dilution of precision
|
|
WGS84
|
World Geodetic System 1984
|
|
1 PPS
|
1 pulse per second
|
