Transcript Lysbilde 1 - Nordic Institute of Navigation

Efficient and accurate surveying with
GPS/Glonass
Satref consists of:
 Permanent GPS/Glonass
reference stations situated
almost all over Norway
 Control centre, located at
NMA, Hønefoss.
What SATREF does:
The SATREF® services continuously model the size of the
effects of different error sources in the GPS and Glonass
systems
 We generate and distribute both real-time reference/correction
data (RTCM) and post processing data (RINEX).
The reference stations
 PGS-B: 16 stations on the Norwegian mainland
+ Ny Ålesund, Jan Mayen, Höfn (Iceland)
 PGS-C: About 60 stations (continuously increasing)
The station coordinates are computed in two
independent ways:
 Precise point positioning (solution in ITRF2005,
transformed to EUREF89)
 GNSS baselines from the 4 closest EUREF89 benchmarks
(landsnett, stamnett)
Satref services accuracy
Your position
Your surveyed position
GPS only
MPOS
22 metres or
better for 95%
of the
measurements
3-5 metres or
better for 95%
of the
measurements
DPOS
3 decimetres
(30
centimetres) or
better for 95%
of the
measurements
CPOS
5 centimetres
or better for
95% of the
measurements
ETPOS
Possible to
achieve
millimetre
accuracy
CPOS: Data flow
IGS
Predicted
ephemeris
data
GNSS raw observation
(and ephemeris) data
from
the reference stations
Reference data (RTCM)
SATREF® control centre
GNSS
position
(NMEA)
GNSS rover
Data processing
 Sofware: Trimble GPSNet
 Input:
GNSS raw observation data
Predicted (and broadcast) ephemeris data
Known station coordinates
 Network processing between the
stations  error models (“network
corrections”) are created
The VRS principle (I)
Ref. station
Virtual
ref. station
(VRS)
The VRS principle (II)
Network-RTK in CPOS are operated in the same
way as traditional RTK, but a mobile reference
receiver is replaced by a virtual reference station
(VRS). CPOS uses one of the first NMEA positions it
gets from the user as a VRS.
The reference data from the VRS are based on the
nearest physical stations.
The CPOS software takes the observation data from
the nearest physical station, modifies them by the
network corrections and transforms them to the
VRS position.
The VRS principle (III)
Ref. station
Virtual
ref. station
(VRS)
GNSS rover
Connecting to CPOS
 GPS only
 Mobile phone
 GSM
 Internet
 NTRIP protocol
• This reduces
telecom. costs
• Most users
today connect
via GPRS on a
mobile phone,
but there are
alternatives
 GPS+Glonass
(full coverage
autumn 2008)
All combinations are possible
Reference data format
RTCM v2.3 (CPOS via mobile phone with GPS
only)
 Contents (in brief):




Pseudorange “measurements”
Carrier phase “measurements”
Position of the VRS + “antenna” description (“null-antenna”)
Position of the nearest physical reference station
RTCM v3 (all other CPOS varieties)
 Contents (in brief):





Pseudorange “measurements”
Carrier phase “measurements”
Position of the VRS + “antenna” description (“null-antenna”)
Position of the nearest physical reference station
Residual messages from the model interpolation
What are the SATREF services used for?
Land surveying
Navigation
Machine guidance
Registration
Flight positioning
for
photogrammetry,
laser scanning
etc.
Retrieving
Documentation
Who are the users of CPOS?
Municipalities
Energy
Governmental
Private surveying
Contractors
Quarrying/mining
Others
CPOS today
 Today there are more than 400 users
 CPOS is offered to the entire country, but is only established when there is a
sufficient market.
 Establishing and management are financed by the users:
 4 users per station established, 2 years commitment and 20000 NOK (approx. 2500
EUR) + VAT each year
 Discount for customers with several users:
•
•
3 – 10 users: 15000 NOK
>= 11 users: 13000 NOK
 The SATREF services are non-profit services. This means that a possible
profit in the short run is used to
 reduce the prices
 upgrade existing reference stations
 establish more reference stations
CPOS coverage areas
Areas
covered
during
2008
CPOS in the future
 Goals for 2015:
Coverage area: The 95% most populated
areas in Norway + important
infrastructure areas (roads, rail)
1 cm 3D accuracy with a relatively high
level of integrity
Additional use of the reference stations
 GNSS observation data from the stations are used in
 Monitoring and analysing the performance of EGNOS at
northern latitudes
 Making a Norwegian ionosphere model
 Meteorology
 Monitoring crust movements
• Plate tectonics
• Post-glacial rebound (land uplift)
 Some stations give observation data to IGS, EUREF and other
organisations/institutions
 All this means that we have to make sure that the quality of
the stations is as good as possible