Integration of Earth rotation, geometry and gravity field using space geodetic observations

• Applicants: Dr.-Ing. Detlef Angermann; Professor Dr. Markus Rothacher
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: from 2006 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5471782

• Final Report Year: 2016

Final Report Abstract

In this Project P6 of the research unit FOR584 advanced methods for a combined estimation of the rotation, the geometry and the low-degree spherical coefficients of the gravity field of the Earth has been developed. Based on unified standards for the modelling and parameterization homogeneously (re-)processed observation time series of the contributing geodetic space techniques (GNSS, SLR and VLBI) over a time span of 13 years were generated. In the first funding phase the project scientist also concentrated on investigations of the geophysical models and on the separation of contributions to Earth rotation variations from the atmosphere, oceans and continental hydrosphere. In the second phase these latter research activities were continued within the Project P9. A focus of Project P6 was on detailed studies of the interactions and correlations between the Earth orientation parameters (EOP), the low-degree spherical harmonic coefficients of the Earth’s gravity field, satellite orbit parameters and the terrestrial reference frame. For this purpose an SLR multi-satellite solution has been computed and the large improvement of the stability of the estimated parameters (compared to a standard LAGEOS 1/2 solution) has been demonstrated. Another highlight was the implementation of a new methodology for the combination of so-called epoch reference frames (ERFs). A major advantage of this new approach is that the non-linear station motions caused by various loading phenomena and other non-linear effects (e.g., postseismic deformations) are much better represented due to the frequent estimation of the station positions (e.g., weekly), compared to a conventional multi-year reference frames (MRF) with constant velocities. Both types of reference frame realizations were studied and it was shown that the neglected (residual) non-linear station motions in the MRF are mapped also in the EOP. The results of Project P6 significantly contributed to lAG’s Global Geodetic Observation System (GGOS) and to its key goal, the integration of geometry, rotation and gravity field of the Earth, which was also one of the key goals of the research unit (goal Z5). P6 also contributed to improve the data base and quality (Z6), the interaction between high-frequency and episodic signals in Earth rotation and processes in the Earth system (Z2) and the modelling of the interaction between decadal and secular variations in Earth rotation and Earth processes (Z3). The Project P6 provided fundamental results for other projects within this research unit (primary P1. P5. P8 and P9).

Publications

• (2006): Reprocessing of a global GPS network. Journal Geophysical Research, Vol. 111, B05402
  Steigenberger P., Rothacher M., Rülke A., Pritsche M., Vey S.
  
• (2007): Advances in terrestrial reference frame computations. In: Tregoning P., Rizos C. (eds.) Dynamic Planet, lAG Symposia, Vol. 130: 595-602, Springer
  Angermann D., Drewes H., Krügel M., Meisel B.
  
• (2007): Combined Earth orientation parameters based on homogeneous and continuous VLBI and GPS data. In: Schuh H., A. Nothnagel, C. Ma (Eds.): VLBI special issue. Journal of Geodesy
  Thaller, D., M. Krügel, M. Rothacher, V. Tesmer, R. Schmid, D. Angermann
  
• (2007): Frontiers in the combination of space geodetic techniques. In: Tregoning P., Rizos C. (eds.) Dynamic Planet, lAG Symposia, Vol. 130, 158-165, Springer
  Krügel M., Angermann D.
  
• (2008): Realization of the Terrestrial Reference System by a reprocessed global GPS network. Journal of Geophysical Research
  Rülke A., Dietrich R., Fritsche M., Rothacher M., Steigenberger P.
  
• (2009): Contribution of non-tidal oceanic mass variations to polar motion determined from space geodesy and ocean data, in: Sideris, M.G. (ed.) Observing our Changing Earth, lAG Symposia, Vol. 133: 439-445, Springer
  Göttl F., Seitz F.
  
• (2009): DGFI combination methodology for ITRF2005 computation. In: Drewes, H. (Ed.): Geodetic Reference Frames, lAG Symposia, Vol. 134: 11-16
  Angermann D., Drewes H., Gerstl M., Krügel M., Meisel B.
  
• (2009): On the strengths of SLR observations to realize the scale and origin of the terrestrial reference system. In: Sideris, M.G. (Ed.): Observing our Changing Earth, lAG Symposia, Vol. 133: 21-27
  Angermann D., Müller H.
  
• (2009): Rigorous variance component estimation in weekly intra-technique and inter-technique combination for global terrestrial reference frames. In: Drewes H. (Ed.) Geodetic Reference Frames, lAG Symposia 134: 39-44, Springer
  Keim R.
  
• (2009): The actual plate kinematic and crustal deformation model APKIM2005 as basis for a non­rotating ITRF. In: Drewes, H. (Ed.): Geodetic Reference Frames, lAG Symposia, Vol. 134: 95-99, Springer
  Drewes H.
  
• (2011): GGOS-D: homogeneous reprocessing and rigorous combination of space geodetic observations. Journal of Geodesy 85(10): 679-705
  Rothacher M., Angermann D., Artz T., Bosch W., Drewes H., Boeckmann S., Gerstl M., Keim R., Koenig D., Koenig R., Meisel B., Mueller H., Nothnagel A.. Panafidina N., Richter B., Rudenko S., Schwegmann W., Seitz M., Steigenberger P., Tesmer V., Thaller D.
  
• (2012): The 2008 DGFI realization of the ITRS: DTRF2008. Journal of Geodesy 86(12), 1097-1123
  Seitz M., Angermann D., Bloßfeld M., Drewes H., Gerstl M.
  
• (2013): Alternative definitions of the terrestrial reference system and its realization in reference frames. In: Altamimi Z., Collilieux X. (Eds.) Reference Frames for Applications in Geosciences, lAG Symposia. Vol. 138: 39-44, Springer
  Drewes H., Angermann D., Seitz M.
  
• (2013): Global terrestrial reference systems and their realizations. In: Xu G. (Ed.) Sciences of Geodesy II - Innovations and Future Developments, 97-132, Springer
  Angermann D., Seitz M., Drewes H.
  
• (2014): Non-linear station motions in epoch and multi-year reference frames. Journal of Geodesy 45-63, Springer
  Bloßfeld M., Seitz M., Angermann D.
  
• (2014): Systematic effects in LOD from SLR observations. Advances in Space Research 54(6): 1049-1063
  Bloßfeld M., Gerstl M., Hugentobler U., Angermann D., Müller H.
  
• (2015): Second-degree Stokes coefficients from multi-satellite SLR. Journal of Geodesy 89{9): 857-871
  Bloßfeld M., Müller H., Gerstl M.. Stefka V., Bouman J., Götti F., Horwath M.
  
• (2015): Separation of atmospheric, oceanic and hydrological polar motion excitation mechanisms based on a combination of geometric and gravimetric space observations. Journal of Geodesy B9{A): 377-390, Springer,
  Göttl F., Schmidt M.. Seitz F.. Bloßfeld M.
  
• (2016): Satellite laser ranging - a tool to realize GGOS? In: Rizos C.. Willis P. (Eds.) lAG 150 Years. lAG Symposia, Vol. 143: 540-547
  Bloßfeld M., Stefka V., Müller H., Gerstl M.