swisstopo report for egvap 2008/2009

armasuisseSwiss Federal Office of Topography swisstopo

swisstopo Report for EGVAP 2008/2009

E. Brockmann

2 Swiss Federal Office of Topography swisstopo

swisstopo Report 2009 for EGVAP

Content

• Routine GNSS operation: - Status report: Processing, availability- Comparison with radio sondes- Study of the influence of snow

• Tomography approach (project MeteoSwiss, ETH Zurich with ZTD data + double-difference data from swisstopo; results prepared by D. Perler, ETH Zurich)



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Processing remarks

• Bernese Software 5.0 (+) – close cooperation with University of Berne

• Same strategy since November 2006 (GPS week 1400)• Number of sites (and satellites) slightly increased – not yet

analyzed 6 super stations included Nov. 12, 2008

~90 sites32 + 15 sat.

~90 sites



GNSS processing

• Since Nov. 06: GPS+GLONASS combined processing• Mid 2007: Permanent network in Switzerland enhanced

(GPS-GLONASS combined receivers installed)• Since Oct. 07: ambiguity resolution for hourly processing

• [March 2008: absolute antenna model, 3 degrees elevation cut-off, gradient estimation, GNSS as input for tomography]

• Today (Nov. 09): 32 GPS and 15 GLONASS satellites – March, 2009 the magic number of 51 GNSS was reached

Baseline length strategy Fixed Ambiguities

0 - 20 km L1/L2 95 - 100%

20 - 200 km L5/L3 90 - 100%

200 - 2000 km QIF *) 70 – 80%



Processing remarks (2)

• rms of unit weight estimated for the GPS phase observables: higher during summer times – evtl. Meteo more difficult to model (?)

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EUMETNET – EUREF – MOU: swisstopo use• signed in London, June 2007:

Data exchange and usage of radiosonde and synop (meteo) for geodetic scientific use

• Routinely 13 collocations with radio sonde data analyzed at swisstopo

GNSS site

RS site



GNSS validation: PAYEReference: PP, GNSS, absolute antenna PCV

GLONASS influence is small for daily PP amb-fix solutions

Relative antenna model causes bias

RRT solution with bigger variations (small network)



Validation using different processing options and external sources

Radio sonde comparison of 13 sites: ~ positve bias last weeks



Validation with radio sonde data: PAYE• reference: GNSS postprocessing• Absolute antenna phase center related since Mid 2007

Trimble Cephyr antenna• Seasonal variations clearly visible



Radio sonde – GPS: PAYE (D. Perler)

• Relative antenna phase center till March 2008• Antenna change (GPS -> GLONASS): June 2007

Trimble Microcentered TRM33429.20+GP -> Cephyr antenna TRM55971.00 ( )

• Jump + seasonal variations + day/night differences substracted



Radio sonde – GPS: PAYE (D. Perler)

• Results from 2 years: 0:00, 12:00 UTC measurements• Mean ZTD with seasonal variations substracted

• At noon: ZTD of radio sonde is 6 mm smaller as GPS

Radio sonde GPS

day: 12:00 UTC 2.2832 ± 0.0011 m 2.2893 ± 0.0012 m

night: 0:00 UTC 2.2945 ± 0.0011 m 2.2929 ± 0.0012 m

night - day difference

0.0114 ± 0.0015 m 0.0036 ± 0.0017 m

???

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Validation with radio sonde data: PAYE • reference: Real-time monitoring• All plots available on http://www.swisstopo.ch/pnac – similar

monitoring system as EGVAP with traffic light symbols• Radio sonde data with a time delay available



Availability

• Meteo processing and coordinate monitoring closely related• Availability is important: 99.66% LPT_; 96.49% LPTR

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Example heavy snow fall: PAYE

December 2008 - Status

PAYE



Example heavy snow fall: PAYE (2)

December 2008 – coordinates 20 cm off (height) !

1 point = 1 hour1 point = 1

hour1 point = 30 Seconds (kinem.)

Positioning service monitor




December 2008 - ZTDs

• ZTD parameters are highly biased in case of heavy snow falls – as also the corresponding coordinates…




December 2008 – ZTDs eliminated in postprocessing




• Antennas are quite sensitive to surrounding – replacement of 6 antennas in May 2009 with chokering antennas (after extensive snow tests in the Alps); further antenna replacements planned.

Case 2, January 2009 – picture of the antenna – only a small bias in the coordinates (3 cm in height)



Tomography

• GANUWE Project- Swiss project funded by the Swiss Federal Office of the

Environment FOEN- Partners: ETH Zurich + MetoSwiss- External partner: swisstopo

• Goal: Make tomography usable in numerical weather prediction

• Follow up project of phD (Kruse, Troller) and “local networks” (Lutz)

• Results prepared by D. Perler (ETHZ)



Improvements

• Data- GLONASS supported- ZTD estimates based on

absolute phase center variations

- More GNSS stations• Computational

- Kalman filter implementation (instead collocation)

- Voxel parametrization (constant, multi-linear, spline)

- Simulator (point measurements, ZTD, Slant-delay, Double-differences)

Simulation of more satellite systems:gain for GNSS tomography



GNSS tomography: data flow

GNSS-double-differences

GNSS-ZTD

Surface meteo

Radio sondes

measurements

Tomographysoftware

AWATOS 2Weather model

Spectrometer

MeteoSwiss

swisstopo

MeteoSwiss



Results with real Data from the GPS Network

• Comparison between tomographic solutions and radio sounding observations

• Non-constant parameterized solutions have smaller standard deviation than the constant parameterized ones.

• Spline/bilinear solution at noon oscillates above 6km.



Results with data from the GPS network

video

• Outlook:

project with dense network (2-3 km resolution) and low-cost L1 receiver planned



“Climatology” for Geodesists

downward movementrise

1 mm/yrDerived from10 years GPS analysis

Thank you for your attention

swisstopo report for egvap 2008/2009

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