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92 Commission 3 – Earth Rotation and Geodynamics 3. Combination of different observation techniques Earth orientation parameters (EOP) based on homogeneous and continuous VLBI and GPS data were consistently combined by THALLER et al. (2006b) using techniquespecific datum-free normal equation systems. Especially the rigorous combination of UT1-UTC and LOD delivered by VLBI and GPS revealed that both techniques perfectly complement each other and the applied combination did not suffer from systematic effects present in the GPSderived LOD values. The local geodetic ties between GPS and VLBI antennas generally play an essential role within the inter-technique combination. Several studies already disclosed non-negligible discrepancies between terrestrial measurements and space-geodetic solutions. THALLER et al. (2006b) demonstrated to what extent these discrepancies propagate into the combined EOP solution. An overview of the combination studies performed by the Forschungseinrichtung Satellitengeodäsie der TU München (FESG) and the Deutsches Geodätisches Forschungsinstitut (DGFI) based on the data of the continuous IVS campaign CONT02 was given by THALLER et al. (2006a). The cooperation of the two institutions established the basis for a detailed adaption of GPS and VLBI software concerning models and parameterization to avoid systematic differences between the technique contributions. Regarding sub-daily earth rotation parameters the study emphasizes that a combination of the space techniques improves the results compared to single-technique solutions significantly. Furthermore, THALLER et al. (2006a) described a combination scheme for long sub-daily EOP time series from VLBI and GPS removing the weakness of UT1 estimations of satellite techniques and, consequently, offering the opportunity to study sub-daily tidal excitations and the influence of high-frequency or episodic geophysical effects on earth rotation. In a joint effort the Technical Universities of Munich and Dresden performed a reprocessing of a global GPS network over the last decade in order to dispose existing inhomogeneities and inconsistencies of GPS time series of global geodetic parameters due to changes at the individual International GNSS Service Analysis Centers hampering geophysical interpretations of these long time series. According to STEIGENBERGER et al. (2006), first results of the reprocessing of 11 years of data showed significant improvements in the quality and homogeneity of estimated parameters, and formal errors of sub-daily earth rotation parameters could be reduced by 30%. In addition, advanced modelling approaches of second- and third-order ionospheric corrections and absolute antenna phase center corrections for receivers and satellites were tested to achieve further improvements. 4. Analysis and prediction Results of the analysis of earth rotation data derived from the continuous VLBI campaign CONT02 were presented by HAAS and WÜNSCH (2006). Regarding high-frequency variations, 40-60% of polar motion and about 80% of UT1 could be explained by the ocean tide model of Ray. The remaining residuals were found to be on the level of several tens of micro-arcseconds. So far, they cannot be reproduced completely by models based on non-tidal angular momentum, atmospheric tides and luni-solar torques acting on the tri-axial earth. However, the diurnal signal detected in polar motion residuals could partly be explained by models due to non-tidal angular momentum and atmospheric tides. In the residuals of polar motion from CONT02 the authors identified third-diurnal variations close to the S3 tide constituent with retro- and pro-grade amplitudes on the order of 40 mas, what is much larger than predictions based on atmospheric effects. With respect to the diurnal frequency band in UT1 the agreement between theoretical models and observations was also poor and the empirical values were generally larger than the modeled ones. GUO et al. (2005b) investigated the double peak of the Chandler wobble (CW) in the spectrum of polar motion by comparing the polar motion data series (annual wobble removed) with a synthetic double-frequency CW time series. They observed a reasonable agreement between their peak times, which is an argument for the hypothesis of a double frequency CW, but is inconclusive with regard to whether the CW really has two frequencies. For the determination of the spectral properties of polar motion data a folding averaging algorithm (FAA) presented by GUO et al. (2005c) was used. By means of an adaptive network based fuzzy inference system (ANFIS), AKYILMAZ and KUTTERER (2003, 2004) studied the short-term prediction of earth rotation parameters up to 40 days into the future; applying a similar approach, AKYILMAZ and KUTTERER (2005) extended the prediction period to one year. After removing well-known influences such as solid earth and ocean tide effects as well as seasonal atmospheric variations from the daily time series ERP C04 provided by IERS, the residual values were used for both training, i.e., optimization of parameters, and validation, i.e., comparison of predicted data with independent observed data, of the network. A comparison of predicted LOD and polar motion values with corresponding results from other methods, e.g., artificial neural networks (ANN), revealed root-mean-square errors which were equal or even lower than those from the other considered methods. The authors emphasized that the advantage of the applied prediction method lies not only in the high precision, but also in a comparatively easy handling. However, despite its significantly reduced complexity, ANFIS modelling is still more complicated than several other methods, such as, for example, the one used in the IERS EOP service. References AKYILMAZ O., KUTTERER H. (2003): Prediction of earth orientation parameters by fuzzy inference systems. DGFI Report, No. 75, München. AKYILMAZ O., KUTTERER H. (2004): Prediction of earth rotation parameters by fuzzy inference systems. Journal of Geodesy, Vol. 78/1-2, S. 82-93. AKYILMAZ O., KUTTERER H. (2005): Fuzzy inference systems for the prediction of earth rotation parameters. In: Sanso, F.
M. Thomas, M. Soffel, H. Drewes: Earth Rotation – Theory and Analysis 93 (Ed.): A Window on the Future, Proceedings of the 36th IAG General Assembly, 23rd IUGG General Assembly, Sapporo, Japan, 2003, IAG Symposia series, No. 128, S. 582-588. ENDLER C. (2007): Untersuchung zu Variationen der Tageslänge (LOD) und ihrer Beziehung zu ENSO auf der interannualen Skala:Master Thesis, Fachbereich Geowissenschaften, Freie Universität Berlin, Berlin. ENGELS J. (2006): Zur Modellierung von Auflastdeformationen und induzierter Polwanderung. Universität Stuttgart, Schriftenreihe der Institute des Studiengangs Geodäsie und Geoinformatik, Report Nr. 2006.1, Stuttgart. GREINER-MAI H., JOCHMANN H., BARTHELMES F., BALLANI L. (2003): Possible influences of core processes on the Earth's rotation and the gravity field. Journal of Geodynamics 36, 343-358. GREINER-MAI H., BALLANI L., STROMEYER D. (2004): The poloidal geomagnetic field in a differentially rotating upper core layer. Geophysical Journal International 158, doi:10. 1111/j.1365-246X.2004.02343.x, 864-873. GUO J-Y., GREINER-MAI H., BALLANI L. (2005a): A spectral search for the inner core wobble in Earth’s polar motion. Journal of Geophysical Research 110, B10402, doi: 10.1029/2004JB003377. GUO J.Y., GREINER-MAI H., BALLANI L., JOCHMANN H., SHUM C.K. (2005b): On the double-peak spectrum of the Candler wobble. Journal of Geodesy, 78, 654-659. DOI 10.1007/ s00190-004-0431-0. GUO J.Y., GREINER-MAI H., DIERKS O., BALLANI L., NEUMEYER J., SHUM C.K. (2005c). Application of the Folding- Averaging Algorithm for the Determination of the Periods of the Earth's Free Oscillation Using Superconducting Gravimeter Data. Bulletin D'information des Marées Terrestres 139, 11025-11036. HAAS R., WÜNSCH J. (2006): Sub-diurnal earth rotation variations from the VLBI CONT02 campaign, J. of Geodyn., Vol. 41, 94-99. JOCHMANN H. (2003): Period variations of Chandler wobble. Journal of Geodesy 77, 454-458. DOI 10.1007/s00190-003- 0347-0 LEHMANN E., ENDLER C., LECKEBUSCH G.C., ULBRICH U., NEVIR P. (2007): LOD – An independent indicator for climate variability and change? EGU General Assembly, Vienna, 2007, (http://www.cosis.net/abstracts/EGU2007/07641/ EGU2007-J-07641.pdf). MÜLLER J., KUTTERER H., SOFFEL M. (2005): Earth Rotation and global dynamic processes – joint research activities in Germany. In: Fundamental Astronomy: New concepts and models for high accuracy observations. Proceedings of the Journees Systemes de reference spatio-temporels (ed. by N. Capitaine), Paris 2004, P. 121-125. SCHUH H., DILL R., GREINER-MAI H., KUTTERER H., MÜLLER J., NOTHNAGEL A., RICHTER B., ROTHACHER M., SCHREIBER U., SOFFEL M. (2003): Erdrotation und globale dynamische Prozesse. Mitteilungen des Bundesamtes für Kartographie und Geodäsie, Band 32, Frankfurt/Main. SEITZ F. (2004): Atmosphärische und ozeanische Einflüsse auf die Rotation der Erde. DGK, Reihe C, Nr. 578. SEITZ F., STUCK J., THOMAS M. (2004): Consistent atmospheric and oceanic excitation of the Earth's free polar motion. Geophys. J. Int., 157, 25-35. SEITZ F. (2005): Zur Anregung der Chandler-Schwingung. Zeitschrift f. Vermessungswesen, 130(3), 166-173. SEITZ F., KUTTERER H. (2005): Sensitivity analysis of the nonlinear Liouville equation. In: Sanso, F. (Ed.): A Window on the Future of Geodesy, Proceedings of the 36th IAG General Assembly, 23rd IUGG General Assembly, Sapporo, Japan, 2003, IAG Symposia series, Vol. 128, S. 601-606, Springer, Berlin.. SEITZ F., STUCK J., THOMAS M. (2005): White noise Chandler wobble excitation. In: Forcing of Polar Motion in the Chandler Frequency Band: A Contribution to Understanding Interannual Climate Variations, H.-P. Plag, et al. (Hrsg.), Cahiers du Centre Européen de Géodynamique et de Séismologie, Vol. 24, 15-21, Luxembourg. STEIGENBERGER P., ROTHACHER M., DIETRICH R., FRITSCHE M., RÜLKE A., VEY S. (2006): Reprocessing of a global GPS network. Journal of Geophysical Research, Vol. 111, B05402. STUCK J., SEITZ F., THOMAS M. (2005): Atmospheric forcing mechanisms of polar motion. In: Forcing of polar motion in the Chandler frequency band: A contribution to understanding interannual climate variations, Plag, H.-P., B. Chao, R. Gross, and T. van Dam (eds.), Cahiers du Centre Européen de Géodynamique et de Séismologie, Vol. 24, 127-133, Luxembourg. THALLER D., DILL R., KRÜGEL M., STEIGENBERGER P., ROTHACHER M., TESMER V. (2006a): CONT02 Analysis and Combination of Long EOP Series. Observation of the Earth System from Space, Flury, Rummel, Reigber, Rothacher, Boedecker, Schreiber (Hrsg.), pp. 389-411, Springer Verlag, Berlin Heidelberg. THALLER D., KRÜGEL M., ROTHACHER M., TESMER V., SCHMID R., ANGERMANN D. (2006b): 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, DOI 10.1007/s 00190-006-0115-z. THOMAS M., DOBSLAW H., STUCK J., SEITZ F. (2005): The ocean's contribution to polar motion excitation – as many solutions as numerical models? In: Plag H.P. et al. (Eds.): Forcing of polar motion in the Chandler frequency band: A contribution to understanding inter-annual climate variations, Cahiers du Centre Européen de Géodynamique et de Séismologie, Vol. 24, 143-148, Luxembourg, 2005. THOMAS M., DOBSLAW H., SOFFEL M. (2007): The ocean's response to solar thermal and gravitational tides and impacts on EOP. In: Proceedings of Les Journes 2005, N. Capitaine (ed.), Paris Observatory, 2007. WALTER C. (2005): Globale kontinentale Wasserabflüsse und ihr Einfluss auf die Anregung der Erdrotation. In: BfG-Veranstaltungen "Anwendungen der weltweiten Sammlung von Abflussdaten des Global Runoff Data Centre (GRDC)", BfG-Veranstaltungen 4/2005, 48-55. WEIS P. (2006): Ocean Tides and the Earth's Rotation – Results of a High-Resolving Ocean Model forced by the Lunisolar Tidal Potential. Max-Planck-Institute for Meteorology, Reports on Earth System Science 36, 111 p.
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DEUTSCHE GEODÄTISCHE KOMMISSION be
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Adresse des Herausgebers / Address
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Contents Commission 1 - Reference F
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COMMISSION 1 REFERENCE FRAMES 7
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10 Commission 1 - Reference Frames
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14 Introduction Celestial Reference
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24 Introduction The contributions o
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28 Satellite altimetry provides a p
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COMMISSION 2 GRAVITY FIELD 33
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36 Commission 2 - Gravity Field res
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38 Commission 2 - Gravity Field aut
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40 Commission 2 - Gravity Field in
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Page 46 and 47: 44 Commission 2 - Gravity Field KRE
Page 48 and 49: 46 Commission 2 - Gravity Field Dev
Page 50 and 51: 48 Commission 2 - Gravity Field ILK
Page 52 and 53: 50 Introduction In the reporting pe
Page 54 and 55: 52 Commission 2 - Gravity Field of
Page 56 and 57: 54 Commission 2 - Gravity Field GRU
Page 58 and 59: 56 Commission 2 - Gravity Field LEM
Page 60 and 61: 58 1. Modelling Techniques Fundamen
Page 62 and 63: 60 Commission 2 - Gravity Field BUN
Page 64 and 65: 62 Commission 2 - Gravity Field Geo
Page 66 and 67: 64 Commission 2 - Gravity Field SCH
Page 68 and 69: 66 Commission 2 - Gravity Field gra
Page 70 and 71: 68 Commission 2 - Gravity Field LOM
Page 72 and 73: 70 Introduction The four years sinc
Page 74 and 75: 72 Commission 2 - Gravity Field met
Page 76 and 77: 74 Commission 2 - Gravity Field SCH
Page 79 and 80: Introduction The determination of E
Page 81 and 82: Introduction German investigations
Page 83 and 84: In Europe, there are detailed inves
Page 85 and 86: SASGEN, I., MULVANEY R., KLEMANN V.
Page 87 and 88: enabling us to map the behaviour of
Page 89 and 90: NAUJOKS M, JAHR T., JENTZSCH G.,. K
Page 91 and 92: nental hydrosphere. Thus, interpret
Page 93: M. Thomas, M. Soffel, H. Drewes: Ea
Page 97 and 98: observed that the resulting masscha
Page 99 and 100: Since 2001, the IERS Central Bureau
Page 101 and 102: COMMISSION 4 POSITIONING AND APPLIC
Page 103 and 104: The main highlights in the past fou
Page 105 and 106: VLBI Space Geodetic Techniques (VLB
Page 107 and 108: A. Nothnagel: Space Geodetic Techni
Page 109 and 110: A. Nothnagel: Space Geodetic Techni
Page 111 and 112: also be able to track the broadband
Page 113 and 114: CHEN X., DEKING A., LANDAU H., STOL
Page 115 and 116: SEEBER G.: Beitrag für „Directio
Page 117 and 118: 2003, WÜBBENA et al. 2006a) or in
Page 119 and 120: Permanent GNSS Networks, including
Page 121 and 122: G. Weber, M. Becker, J. Ihde: Perma
Page 123 and 124: G. Weber, M. Becker, J. Ihde: Perma
Page 125 and 126: General remarks The continuous and
Page 127 and 128: Introduction GNSS Based Sounding of
Page 129 and 130: J. Wickert, N. Jakowski: GNSS Based
Page 131 and 132: J. Wickert, N. Jakowski: GNSS Based
Page 133 and 134: References ADAM N.: TerraFirma Qual
Page 135 and 136: Introduction The period 2003 - 2007
Page 137 and 138: procedures and surveying instrument
Page 139 and 140: Motivation During the last years, n
Page 141 and 142: AVILA-RODRIGUEZ J.-A., PANY T., EIS
Page 143 and 144: SEIFERT A., KLEUSBERG A. (2003): An
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IAG PROJECTS 143
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The Global Geodetic Observing Syste
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KRÜGEL M., TESMER V., ANGERMANN D.
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Inter-commission Committees (ICC) A
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After the restructuring of the IAG
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Introduction Physical Aspects of Ge
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H. Drewes, M. Soffel: Physical Aspe
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W. Keller, W. Freeden: Mathematical
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W. Keller, W. Freeden: Mathematical
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H. Kutterer, W.-D. Schuh: Quality M
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B. ICC on Planetary Geodesy (ICCPG)
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Introduction Various space missions
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Photogrammetrie, Fernerkundung und
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