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E. BrockmannEGS Nice, April 2002
Applications of the real-time Swiss permanent GPS network 'AGNES'
E. Brockmann, S. Grünig, R. Hug, D. Schneider, A.Wiget and U. Wild
www.swisstopo.ch
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E. BrockmannEGS Nice, April 2002
Contents
• AGNES network– History– Stations– Concept
• Conclusions
• Applications– Surveying– Geodynamics– Meteorology– Positioning
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E. BrockmannEGS Nice, April 2002
History
• 1989-1992: GPS based first order network (104 sites)
Accuracy: 0.5 - 1.0 cm horizontally
2.0 - 3.0 cm vertically• 1995: Definition of CHTRS95 (equal ETRS89 at epoch
1993.0)
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April 2002
0 km 20 km 40 km 60 km 80 km 100 km
Swiss first order network (1989-1992)
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E. BrockmannEGS Nice, April 2002
History (2)
• 1998: re-measuring of LV95 (CHTRF98); differences below < 1 cm horizontally and < 3 cm vertically
• 1998: Start of the project with 8 permanent stations• 2001: Completion with 29 permanent stations
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E. BrockmannEGS Nice, April 2002
AGNES stations C
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E. BrockmannEGS Nice, April 2002
AGNES network
29 stations
Density of 50 km
• Positioning• Reference frame• Scientific
– GPS meteo– Geodynamics
Applications
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E. BrockmannEGS Nice, April 2002
AGNES network (2)
PNAC Monitor computer
LAN SWISSTOPO
AGNES-Station 1
Communication computer
Access server
GSM
WWW server
Internet
AGNES-Station 2
AGNES-Station ...
AGNES-Station 21
LAN BIT
Firewall
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KOMBV
Real-timePositioning
Post-Proc.Positioning
Scientific Applications• Reference frame
• Geodynamics
• GPS meteo
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“Daily /hourly” “Second”
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E. BrockmannEGS Nice, April 2002
AGNES GPS equipment
• Trimble 4000SSi, Trimble 4700 and Leica System 530 receivers
• Different antenna types (Choke Ring, Microcentered L1/L2, Zephyr), no radomes
• Individual antenna calibration
(relative to “Choke” Ring and “Geodetic” antenna)
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E. BrockmannEGS Nice, April 2002
Surveying
• First order network and densification campaigns are integrated in the permanent network
• Advantages: – Fewer neighboring sites to be measured (only 1 control site instead
of 3 neighboring sites)– Better integration due to time series of the reference stations
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E. BrockmannEGS Nice, April 2002
CHTRF 98CHTRF 98 Teil 1CHTRF 98 Teil 2CHTRF 98 Teil 3LHN95 EmmentalLHN95 Sustenpass
Luzern 99Bern 99
Saas Fee 99
Surveying C
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E. BrockmannEGS Nice, April 2002
Geodynamics
• Permanent Network Analysis Center (PNAC) at the Swiss Federal Office of Topography (swisstopo)
• Automated processing of all AGNES stations + 19 European tracking stations (contribution to EUREF and reference frame maintenance in Switzerland)
EUREF EUREF + AGNES
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E. BrockmannEGS Nice, April 2002
• Results updated daily / weekly :– Coordinates/Covariance
(SINEX format)
– Troposphere parameters (SINEX format)
– Time series, velocity fields
PNAC productshttp://www.swisstopo.ch/geoaktuell/en/pnac.htm
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E. BrockmannEGS Nice, April 2002
Time series: Zimmerwald (ZIMM)
2 cm
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E. BrockmannEGS Nice, April 2002
Time series: Bolzano (BZRG) Earthquake in Northern Italy, July 15, 2001 15:06 UTC, Magnitude: 4.8
2 cm
?
Antenna change
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E. BrockmannEGS Nice, April 2002
Time series: Samedan (SAME)
2 cm
? ?
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E. BrockmannEGS Nice, April 2002
Velocity field in ITRF00 (rel. ZIMM)
Velocities for sites with time series > 0.5 years
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E. BrockmannEGS Nice, April 2002
Alpine network
• Collaboration of BKG, OLG, CNRS, IGN, UPAD, LPT for deriving a dense Alpine dynamic model
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E. BrockmannEGS Nice, April 2002
Excursion: Antenna calibrations
L2 North
Microcentered
antenna
(w.r.t IGS values)
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E. BrockmannEGS Nice, April 2002
Antenna calibrations (2)
Elev.-dep.
corrections
Microcentered
antenna
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E. BrockmannEGS Nice, April 2002
Impact of individual antenna models
Zimm: Choke Ring
-1.0 mm North
2.5 mm Up2.5 mm East
STAB: Zephyr
-0.5 mm North
-8.0 mm Up
1.5 mm East
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E. BrockmannEGS Nice, April 2002
GPS meteorology
• Partners in Switzerland:
– MeteoSwiss– University of Berne (IAP)– Swiss Federal Institute of Technology (ETH) Zurich
– COST 716:Exploitation of ground-based GPS for climate and numerical weather prediction applications
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E. BrockmannEGS Nice, April 2002
Hourly processing• Since Dec. 2001• 50 sites:
– 21 EUREF– 29 AGNES
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• Near real-time results of 6 centers at KNMI: http://www.knmi.nl/samenw/cost716/
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E. BrockmannEGS Nice, April 2002
Numerical weather prediction tests
Integrated water vapor field (Sep. 10, 2001; 15:00 UTC)Without GPS GPS assimilated Difference
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E. BrockmannEGS Nice, April 2002
hourly ... 24-hour average...
± 1 cm
hourly... 7 24-hours ø [150 weeks]
North 16.0 1.0 0.9
East 45.0 4.6 0.8
Up 52.0 5.1 2.5
ZIMM repeatability in [mm]
Coordinate validation in NRT C
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E. BrockmannEGS Nice, April 2002
Next steps
• Establishing hourly processing as an operational service (within COST 716)
• Routine validation (comparison of Swiss LM from weather prediction with GPS)
• More assimilation tests• Quality check of “real” real-time estimates (ZTD estimates from
RTK positioning) every 10 minutes
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E. BrockmannEGS Nice, April 2002
Positioning
• Swiss Positioning Service (swipos®)
– swipos - NAV (1-5 meters)> GPS reference station in Zurich (SRG)
> DGPS correction data (RTCM, Type 1,2 over FM/RDS or GSM)
– swipos - GIS/GEO (cm accuracy)> RTK service over GSM (0900 - Business Number)
> Nationwide cm accuracy!
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E. BrockmannEGS Nice, April 2002
Positioning (2)
• swipos-GIS/GEO is based on the concept of the Virtual Reference Stations (VRS)
• The approximate position of the user is sent to the central communication computer over GSM
Data
Approx. position
Data
Communication Server / VRS Software
Field
FirewallVRS observations(RTCM 18,19)
Data AGNES sites
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E. BrockmannEGS Nice, April 2002
Positioning: Performance tests
• 14 hours test on “swisstopo” roof• 4 hours RAW / VRS performance test (using antenna splitter)• Test in different areas and distances and height differences to the
AGNES network• 2 diploma theses• Praxis tests: determination of 73 second order points using RTK and
“classical” static GPS
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E. BrockmannEGS Nice, April 2002
Positioning: Performance• Test over 14 hours on the swisstopo roof using a
Trimble 5700 receiver (with GSM)• Registration of the RTK position every second;
new initialization every 15 minutes
Horizontal rms: ±1.0 cm (1 σ) Vertical rms: ±1.8 cm (1 σ) Co
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2 cm 2 cm
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E. BrockmannEGS Nice, April 2002
Positioning: Performance (2)
• Test over 4 hours on the swisstopo roof using 2 Trimble 5700 receiver (with 2 GSM) and 1 Zephyr antenna (+ antenna splitter)
• Registration of the RTK position every second; new initialization every 15 minutes
Horizontal rms: ± 0.7 / ± 0.8 cm (1 σ)
Virtuel: 5% float
Raw: 45% float
Vertical rms: ± 3.6 / ± 2.5 cm (1 σ)
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2 cm
2 cm
2 cm
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E. BrockmannEGS Nice, April 2002
Positioning: Performance summary
• 100 seconds to initialization (20 sec. GSM, 80 sec. init.)• Horizontally 2-3 cm rms, vertically 3-4 cm rms• VRS results do not show a smaller bias compared to RAW data of the
nearest AGNES site, but the ambiguity resolution and time to initialization is improved (“factor of 2”)
• 5 satellite constellations for VRS critical (switch to RAW)
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E. BrockmannEGS Nice, April 2002
Conclusions
• The Automated GPS Network Switzerland (AGNES) consists of 29 permanent GPS tracking stations
• AGNES is a multipurpose network:
– Reference network for the first order surveys in Switzerland
– Analysis of time series of coordinates for geodynamics
– 1-hour data processing (near real-time) for meteorological applications (numerical weather prediction)
– swipos-GIS/GEO: RTK positioning service with nationwide cm accuracy
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