Combination - Bernese GNSS Software

The Bernese GPS Software
for the analysis of
GNSS, SLR and VLBI data
and for the
SINEX/NEQ combination
Daniela Thaller 1) , Rolf Dach 1) , Ralf Schmid 2) ,
Urs Hugentobler 2) , Maria Mareyen 3) , Bernd Richter 3)
(1) Astronomical Institute, University of Bern, Switzerland
(2) Technische Universität München, Germany
(3) Bundesamt für Kartographie und Geodäsie, Frankfurt/Main, Germany
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

1. Analysis of observation data
a) GNSS
b) SLR
c) VLBI
Overview
2. Combined GNSS+SLR analysis using satellite co-locations
3. Combination using normal equations (intra- and inter-technique)
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Analysis of GNSS data
Combined GPS+GLONASS analysis is possible with the Bernese GPS
Software (BSW)
Global analysis:
→ CODE: IGS analysis center
→ Final, rapid and ultra-rapid products
→ Operational GPS+GLONASS contribution since May 2003
Regional analysis:
→ EUREF / SIRGAS contributions by most analysis centers
Extension to multi-system GNSS analysis:
→ Different systems (GPS, GLONASS, Galileo, ...)
→ Different/individual observation types per GNSS
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Analysis of SLR data
SLR residual analysis w.r.t. given orbits / EOPs / station coordinates
→ Contribution of AIUB to ILRS as associated analysis center:
SLR residuals w.r.t. GNSS orbits
Extension of the BSW to a full SLR analysis software package:
→ SLR observations to geodetic satellites (mainly Lageos, Etalon)
→ Estimation of SLR-specific parameters (orbits, range biases)
→ ILRS modeling and data handling issues are implemented
Intention: ILRS contribution of BKG generated with BSW
Status: ILRS Benchmark solutions submitted
→ validation process ongoing
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Analysis of VLBI data
Extension of the BSW to a VLBI analysis software package
Simplified VLBI analysis for limited set of VLBI sessions possible:
→ Low degree of automation
→ Simple clock model
→ VLBI-specific effects like telescope deformations not yet implemented
→ Starting from NGS Card Format
Extensions needed to become a full VLBI analysis software package:
→ Estimation of VLBI-specific parameters (e.g., quasar coordinates)
→ Improvement of a priori models and parameterization (e.g., clocks,
telescope deformation)
→ Automation for analysing the entire history of VLBI sessions
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Analysis of VLBI data
Comparison of VLBI-derived troposphere zenith delays with GPS-derived
estimates:
⇒ Remaining differences are not due to deficiencies in the software but
due to unmodeled effects (e.g. uncalibrated radomes)
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Combined GNSS+SLR analysis
Idea: Use satellite co-locations for connecting GNSS and SLR
→ GNSS observations: GPS, GLONASS, (Galileo)
→ SLR observations to GNSS satellites: 2/1 GPS, 3 GLONASS, ???
1. Common parameters:
-
-
-
EOP
Geocenter
Station coordinates
Already done for combination
at NEQ level
- Satellite orbit parameters (dynamical)
2. Needed for connection:
- Stations: Local ties
- Satellite CoM: Vectors to microwave antenna and to laser retroreflectors
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

3D vector difference [mm]
90
80
70
60
50
40
30
20
10
0
Combined GNSS+SLR analysis: Advantages
7090−YAR2
7810−ZIMM
7839−GRAZ
7825−STR1
7825−STR2
7405−CONZ
Comparison of estimated station coordinate differences and local ties
7840−HERS
7840−HERT
8834−WTZR
7105−GODE
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw
7110−MONP
7080−MDO1
7941−MATE
7941−MAT1
7249−BJFS
7501−HARB
Combination GNSS+SLR
AIUB single−technique solutions
Number of SLR observations / 100
→ Connection of techniques either on ground (LT) or in space (orbits)
7501−HRAO
7124−THTI
7845−GRAS
7841−POTS

3D vector difference [mm]
90
80
70
60
50
40
30
20
10
0
Combined GNSS+SLR analysis: Advantages
7090−YAR2
7810−ZIMM
7839−GRAZ
7825−STR1
7825−STR2
7405−CONZ
Comparison of estimated station coordinate differences and local ties
7840−HERS
7840−HERT
8834−WTZR
7105−GODE
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw
7110−MONP
7080−MDO1
7941−MATE
7941−MAT1
7249−BJFS
7501−HARB
GNSS SAO fixed
GNSS SAO estimated
→ Allows transfer of scale information from SLR into GNSS network
→ Estimation of SLR range biases (RGB) together with GNSS satellite antenna offsets
(SAO) is possible
7501−HRAO
7124−THTI
7845−GRAS
7841−POTS

Range bias [mm]
50
40
30
20
10
0
−10
−20
−30
−40
−50
7090
7405
7810
Combined GNSS+SLR analysis: Advantages
Station−specific SLR range biases
7839
7825
7406
7832
GNSS SAO fixed
GNSS SAO estimated
7237
7840
8834
7105
7110
SAO Z−component [mm]
−100
−200
−300
Satellite−specific
−400
0 20 40 60 80 100 120 140
Satellite number
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw
300
200
100
0
SAO corrections for different RGB estimation
GPS
Station−specific
System−specific
GLONASS
→ Allows transfer of scale information from SLR into GNSS network
→ Estimation of SLR range biases (RGB) together with GNSS satellite antenna offsets
(SAO) is possible
→ Estimation of SAO consistently for GPS and GLONASS, and consistently with SLR scale

Common parameters:
- EOP
- Troposphere
- Station coordinates
Combined GNSS+VLBI analysis
Advantages:
- Full EOP information from VLBI transferred to GNSS (polar
motion, UT/LOD, nutation)
- Stabilization of coordinates by common troposphere estimates
→ Benefit already shown for combination at NEQ level
→ Not yet done for combination at the observation level
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Combination using NEQs
General strategy in BSW concerning constraints:
- NO constraints when storing individual NEQs
- Application of constraints only if
a) pre-eliminating parameters
b) generating a solution (before inversion of NEQ)
⇒ Full flexibility for computation of combined solutions
3 equivalent applications within BSW:
- GNSS 1-day analysis ⇒ GNSS n-day solution (e.g. 3-day)
- Separate GNSS/SLR/VLBI analysis ⇒ Combined solution
- SINEX input ⇒ Combined solution
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Combination using NEQs
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Combination using NEQs
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw

Combination using NEQs
Working Group on Combination at the Observation Level, 21./22. October 2009, Warsaw