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Reprocessing of a Global GPS Network ? Experiences
and Results
M. Fritsche, R. Dietrich, A. Rülke Institut für
Planetare Geodäsie (IPG), Technische Universität
Dresden, Germany
P. Steigenberger Institut für Astronomische und
Physikalische Geodäsie, Technische Universität
München, Germany
M. Rothacher GeoForschungsZentrum Potsdam (GFZ),
Germany
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Outline

• Basic Facts Database, Software, Resources
• Observation Modeling and Adjustment
• Results
• Conclusions

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Basic Facts
Project funded DeutscheForschungsGemeinschaft,
2003-2006 Processed period January 1994
December 2007 GPS data 202 nominal GPS
stations Software modiefied Bernese GPS
Software Version 5.0 Strategy modified
processing scheme adapted from CODE IGS
Analysis Center
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Basic Facts

• Processing on Cluster of Linux PCs
• 1-day solution 2.5h from raw level
• 1-day solution 15min from screened DD-level
• 7-day solution 2h on NEQ level

• Labor input invested 15000 man hours
• 40 software development and processing setup
• 40 data handling and screening
• 20 analysis of results and publication

• Results
• 3 complete processing runs
• 20 additional solutions based on 1-day solutions

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Modeling and Adjustment
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Modeling and Adjustment
Higher-order ionospheric effects
mean coordinate residuals for the year 2002
(GRL, Fritsche et al. 2005) compared to standard
solution
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Modeling and Adjustment
A Priori Tropospheric Delay
mean NMF-IMFdifferences for 2002 at 5 elevation
(GRL, Vey et al. 2006)
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Modeling and Adjustment
3-day solution
satellite orbits
weekly solution
coordinates, Earth rotation parameter
long term solution
Reference Frame
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Orbit Accuracy
SLR residuals for IGS, CODE and Reprocessing GPS
orbits
(JoG, Steigenberger et al. 2008)
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Coordinate Discontinuities
Equipment change at Horn Point (HNPT)
ASH700936E SNOW
rel. PCVs DU -15.8 mm
AOAD/M_TA_NGS NONE
abs. PCVs DU -0.5 mm
dDU 15.3 mm
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Coordinate Discontinuities
Altogether 134 discontinuities considered
between 1 January 1994 and 31 December 2005
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GPS TRF PDR05

• Terrestrial Reference System Realization
• absolute PCVs for satellites and receiver
  antennas (scale)
• preelimination of weekly satellite arcs (CM)
• station coordinates, velocities NNR w.r.t.
  IGb00
• Xpol, Ypol freely estimated
• spherical harmonics for a surface load
  redistribution

(JGR, Rülke et al. 2008)
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GPS TRF PDR05
Degree-1 Surface Load Coefficients
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GPS TRF PDR05
TRS
space geodetic observations random erros
systematic modeling errors
additional constaints
Comparison of TRFs instead of 14-parameter
transformation weekly 7-parameter transformations
TRF Estimate
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GPS TRF PDR05
Weekly 7-Parameter Transformations w.r.t.
ITRF2000 / ITRF2005
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Conclusions

• Reprocessing results show improved quality and
  homogeneity of estimated parameter time series
• Reference system realization based on
  homogeneously reprocessed GPS observations
• Concept of simultaneous estimation of satellite
  orbits, station positions and large-scale surface
  load deformation in the CM frame

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References
Rülke A., R. Dietrich, M. Fritsche, M. Rothacher,
and P. Steigenberger (2008), Realization of the
Terrestrial Reference System by a reprocessed
global GPS network, J. Geophys. Res.,
doi10.1029/2007JB005231 (accepted)
Steigenberger P., M. Rothacher, M. Fritsche, A.
Rülke and R. Dietrich (2008), Quality of
Reproccessed GPS Satellite Orbits, Journal of
Geodesy, doi10.1007/s00190-008-0228-7 (accepted)
Vey S., M. Fritsche, R. Dietrich, M. Rothacher,
A. Rülke, P. Steigenberger, (2006), Influence of
mapping function parameters on global GPS network
analyses comparison between NMF and IMF, GRL,
doi10.1029/2005GL024361
Steigenberger P., M. Rothacher, R. Dietrich,
Fritsche, M., A. Rülke, and S. Vey, (2006),
Reprocessing of a global GPS network, JGR,
doi10.1029/2005JB003747
Fritsche M., R. Dietrich, C. Knöfel, M.
Rothacher, A. Rülke, S.Vey, P. Steigenberger,
(2005), Impact of higher-order ionospheric terms
on GPS-estimates GRL, doi10.1029/2005GL024342