The 2008 DGFI realization of the ITRS: DTRF2008

A new realization of the International Terrestrial System was computed at the ITRS Combination Centre at DGFI as a contribution to ITRF2008. The solution is labelled DTRF2008. In the same way as in the DGFI computation for ITRF2005 it is based on either normal equation systems or estimated parameters derived from VLBI, SLR, GPS and DORIS observations by weekly or session-wise processing. The parameter space of the ITRS realization comprises station positions and velocities and daily resolved Earth Orientation Parameters (EOP), whereby for the first time also nutation parameters are included. The advantage of starting from time series of input data is that the temporal behaviour of geophysical parameters can be investigated to decide whether the parameters can contribute to the datum realization of the ITRF. In the same way, a standardized analysis of station position time series can be performed to detect and remove discontinuities. The advantage of including EOP in the ITRS realization is twofold: (1) the combination of the coordinates of the terrestrial pole—estimated from all contributing techniques—links the technique networks in two components of the orientation, leading to an improvement of consistency of the Terrestrial Reference Frame (TRF) and (2) in their capacity as parameters common to all techniques, the terrestrial pole coordinates enhance the selection of local ties as they provide a measure for the consistency of the combined frame. The computation strategy of DGFI is based on the combination of normal equation systems while at the ITRS Combination Centre at IGN solutions are combined. The two independent ITRS realizations provide the possibility to assess the accuracy of ITRF by comparison of the two frames. The accuracy evaluation was done separately for the datum parameters (origin, orientation and scale) and the network geometry. The accuracy of the datum parameters, assessed from the comparison of DTRF2008 and ITRF2008, is between 2–5 mm and 0.1–0.8 mm/year depending on the technique. The network geometry (station positions and velocities) agrees within 3.2 mm and 1.0 mm/year. A comparison of DTRF2008 and ITRF2005 provides similar results for the datum parameters, but there are larger differences for the network geometry. The internal accuracy of DTRF2008—that means the level of conservation of datum information and network geometry within the combination—was derived from comparisons with the technique-only multi-year solutions. From this an internal accuracy of 0.32 mm for the VLBI up to 3.3 mm for the DORIS part of the network is found. The internal accuracy of velocities ranges from 0.05 mm/year for VLBI to 0.83 mm/year for DORIS. The internal consistency of DTRF2008 for orientation can be derived from the analysis of the terrestrial pole coordinates. It is estimated at 1.5–2.5 mm for the GPS, VLBI and SLR parts of the network. The consistency of these three and the DORIS network part is within 6.5 mm.

[1]  U. Hugentobler,et al.  Impact of Earth radiation pressure on GPS position estimates , 2012, Journal of Geodesy.

[2]  T. Springer.  Modeling and validating orbits and clocks using the Global Positioning System , 2002 .

[3]  Pascal Gegout,et al.  GGFC Special Bureau for Loading: current status and plans , 2003 .

[4]  Z. Altamimi,et al.  ITRF2005 : A new release of the International Terrestrial Reference Frame based on time series of station positions and Earth Orientation Parameters , 2007 .

[5]  Hansjörg Kutterer,et al.  A comparative analysis of uncertainty modelling in GPS data analysis , 2005 .

[6]  Manuela Seitz.  Kombination geodätischer Raumbeobachtungsverfahren zur Realisierung eines terrestrischen Referenzsystems , 2009 .

[7]  Detlef Angermann,et al.  Advances in terrestrial reference frame computations , 2005 .

[8]  Pascal Willis,et al.  Improving DORIS geocenter time series using an empirical rescaling of solar radiation pressure models , 2009 .

[9]  Jim Long,et al.  Hartebeesthoek Co-location Survey , 2005 .

[10]  Luca Vittuari,et al.  Surveying co-located space-geodetic instruments for ITRF computation , 2004 .

[11]  Hermann Drewes,et al.  Geodetic Reference Frames , 2009 .

[12]  Detlef Angermann,et al.  DGFI combination methodology for ITRF2005 computation , 2009 .

[13]  Galina Dick,et al.  Impact of GPS satellite antenna offsets on scale changes in global network solutions , 2005 .

[14]  Z. Altamimi,et al.  ITRF2008: an improved solution of the international terrestrial reference frame , 2011 .

[15]  Axel Nothnagel,et al.  Conventions on thermal expansion modelling of radio telescopes for geodetic and astrometric VLBI , 2009 .

[16]  Markus Rothacher,et al.  Estimation of nutation using the Global Positioning System , 1999 .

[17]  P. Steigenberger,et al.  GGOS-D: homogeneous reprocessing and rigorous combination of space geodetic observations , 2011 .

[18]  Steffen Schön,et al.  A proposal for modelling physical correlations of GPS phase observations , 2008 .

[19]  Peter Steigenberger,et al.  Generation of a consistent absolute phase-center correction model for GPS receiver and satellite antennas , 2007 .

[20]  P. Steigenberger,et al.  Absolute phase center corrections of satellite and receiver antennas , 2005 .

[21]  Hermann Drewes.  Reference Systems, Reference Frames, and the Geodetic Datum , 2007 .

[22]  Pascal Willis,et al.  DORIS/SLR POD modeling improvements for Jason-1 and Jason-2 , 2010 .

[23]  Richard G. Gordon,et al.  Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions , 1994 .

[24]  Karl-Rudolf Koch,et al.  Parameter estimation and hypothesis testing in linear models , 1988 .

[25]  Detlef Angermann,et al.  ITRS Combination Centre at DGFI - A terrestrial reference frame realization 2003 , 2004 .

[26]  C. Bizouard,et al.  The Combined Solution C04 for Earth Orientation Parameters Consistent with International Terrestrial Reference Frame 2005 , 2009 .

[27]  Hermann Drewes,et al.  The Actual Plate Kinematic and Crustal Deformation Model APKIM2005 as Basis for a Non-Rotating ITRF , 2009 .

[28]  R. Ferland,et al.  The IGS-combined station coordinates, earth rotation parameters and apparent geocenter , 2009 .

[29]  T. Artz,et al.  VLBI terrestrial reference frame contributions to ITRF2008 , 2010 .

[30]  Pascal Willis,et al.  Refining DORIS atmospheric drag estimation in preparation of ITRF2008 , 2010 .

[31]  Pascal Willis,et al.  IDS contribution to ITRF2008 , 2009 .

[32]  P. Tregoning,et al.  Dynamic planet : monitoring and understanding a dynamic planet with geodetic and oceanographic tools : IAG symposium, Cairns, Australia, 22-26 August 2005 , 2006 .

[33]  E. C. Pavlis,et al.  High‐accuracy zenith delay prediction at optical wavelengths , 2004 .

[34]  Leonid Petrov,et al.  Precise geodesy with the Very Long Baseline Array , 2008, 0806.0167.

[35]  Zuheir Altamimi,et al.  ITRF2000: A new release of the International Terrestrial Reference Frame for earth science applications , 2002 .