e. brockmann egs nice, april 2002 applications of the real-time swiss permanent gps network...

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

[email protected]

www.swisstopo.ch


Contents

• AGNES network– History– Stations– Concept

• Conclusions

• Applications– Surveying– Geodynamics– Meteorology– Positioning

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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)


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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AGNES stations C

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AGNES network

29 stations

Density of 50 km

• Positioning• Reference frame• Scientific

– GPS meteo– Geodynamics

Applications

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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”


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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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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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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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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• 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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Time series: Zimmerwald (ZIMM)

2 cm

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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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Time series: Samedan (SAME)

2 cm

? ?

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Velocity field in ITRF00 (rel. ZIMM)

Velocities for sites with time series > 0.5 years

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Alpine network

• Collaboration of BKG, OLG, CNRS, IGN, UPAD, LPT for deriving a dense Alpine dynamic model

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Excursion: Antenna calibrations

L2 North

Microcentered

antenna

(w.r.t IGS values)

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Antenna calibrations (2)

Elev.-dep.

corrections

Microcentered

antenna

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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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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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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/


Numerical weather prediction tests

Integrated water vapor field (Sep. 10, 2001; 15:00 UTC)Without GPS GPS assimilated Difference

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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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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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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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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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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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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


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


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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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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e. brockmann egs nice, april 2002 applications of the real-time swiss permanent gps network...

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