armasuisse Swiss 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)

3 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP 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 sites sat. ~90 sites

4 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP 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 lengthstrategy Fixed Ambiguities kmL1/L % kmL5/L % kmQIF *)70 – 80%

5 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Processing remarks (2) rms of unit weight estimated for the GPS phase observables: higher during summer times – evtl. Meteo more difficult to model (?)

6 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP 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

7 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP GNSS validation: PAYE Reference: 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)

8 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Validation using different processing options and external sources Radio sonde comparison of 13 sites: ~ positve bias last weeks

9 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Validation with radio sonde data: PAYE reference: GNSS postprocessing Absolute antenna phase center related since Mid 2007 Trimble Cephyr antenna Seasonal variations clearly visible

10 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Radio sonde – GPS: PAYE (D. Perler) Relative antenna phase center till March 2008 Antenna change (GPS -> GLONASS): June 2007 Trimble Microcentered TRM GP -> Cephyr antenna TRM ( ) Jump + seasonal variations + day/night differences substracted

11 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP 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 sondeGPS day: 12:00 UTC ± m ± m night: 0:00 UTC ± m ± m night - day difference ± m ± m ??? ?

12 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Validation with radio sonde data: PAYE reference: Real-time monitoring All plots available on – similar monitoring system as EGVAP with traffic light symbolshttp:// Radio sonde data with a time delay available

13 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Availability Meteo processing and coordinate monitoring closely related Availability is important: 99.66% LPT_; 96.49% LPTR average Last 52 weeks

14 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Example heavy snow fall: PAYE December Status PAYE

15 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Example heavy snow fall: PAYE (2) December 2008 – coordinates 20 cm off (height) ! 1 point = 1 hour 1 point = 30 Seconds (kinem.)Positioning service monitor

16 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Example heavy snow fall: PAYE (3) December ZTDs ZTD parameters are highly biased in case of heavy snow falls – as also the corresponding coordinates…

17 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Example heavy snow fall: PAYE (4) December 2008 – ZTDs eliminated in postprocessing

18 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Example heavy snow fall: PAYE (5) 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)

19 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP 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)

20 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP 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

21 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP GNSS tomography: data flow GNSS-double- differences GNSS-ZTD Surface meteo Radio sondes measurements Tomography software AWATOS 2 Weather model Spectrometer MeteoSwiss swisstopo MeteoSwiss

22 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP 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.

23 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP Results with data from the GPS network video Outlook: project with dense network (2-3 km resolution) and low- cost L1 receiver planned

24 Swiss Federal Office of Topography swisstopo swisstopo Report 2009 for EGVAP “Climatology” for Geodesists downward movement rise 1 mm/yr Derived from10 years GPS analysis Thank you for your attention