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66 Commission 2 – Gravity Field gravity field solutions. The methodology to correct the atmospheric non-tidal mass variations was revisited by PETERS (2007). Non-tidal oceanic mass variations of the latest releases of AOD1B are derived from output of the baroclinic ocean model OMCT (Ocean Model for Circulation and Tides) of the Technical University of Dresden which is based on meteorological ocean surface forcing and precipitation and evaporation data. DOBSLAW and THOMAS (2006) showed that the impact of river run-off on global ocean mass redistribution (un-modelled in OMCT) can be neglected. Monitoring the Continental Hydrological Cycle Since during the processing of the GRACE mission data to monthly gravity field solutions known tidal as well as all short-term atmospheric and oceanic mass variations are taken into account, time-variable gravity signals derived from time series of GRACE-only gravity models mainly reflect mass redistribution at the Earth’s surface due the continental hydrological cycle. This was verified in studies on global scales (RAMILLIEN et al., 2005a, 2005b; Schmidt et al., 2006a, 2006b; GÜNTNER et al., 2007) as well as on regional scales such as the monitoring of time variations of regional evapotranspiration rates (RAMILLIEN et al., 2006). In this way, GRACE-derived changes in surface mass anomalies can be expected to contribute to the quantification of the total water budget, which is an obviously underestimated quantity as indicated by the GRACEderived amplitudes of annual and semi-annual signals being larger than predicted by global hydrological models. More recently RAMILLIEN et al. (2007) have analysed seasonal but also interannual change in land water storage over 27 large river basins from GRACE data and found significant negative trends for some of the largest basins indicating water mass loss over the investigated time period. NEU- MAYER et al. (2006) showed a high correlation when combining temporal gravity variations resulting from superconducting gravimeter recordings, GRACE monthly gravity field solutions and global hydrology. To extract hydrological (and other geophysical) mass variability from monthly GRACE gravity field solutions special smoothing techniques have to be applied to the nonphysical meridional-oriented striping in the GRACE geoids and to avoid leakage from neighbouring basins or from the ocean. To this end, MARTINEC et al. (2007) performed a statistical analysis of the temporal variability of the GRACE Stokes potential coefficients and Schmidt et al. (2007) made an accuracy assessment for GRACE derived time variable gravity field solutions. KUSCHE (2007) suggested an approximate decorrelation and non-iso-tropic smoothing of time-variable GRACE-type gravity field models. HOR- WATH and DIETRICH (2006) estimated errors of regional mass variations inferred from monthly GRACE gravity field solutions. As an alternative to the concept based on spherical harmonics FENGLER et al. (2005, 2007) and SCHMIDT et al. (2006) calculated regional high-resolution temporal GRACE gravity models using spherical wavelets. SNEEUW et al. (2003) investigated the space-wise, time-wise, torus and Rosborough representation in gravity modelling. In SASGEN et al. (2007) a method based on Wiener filtering applied for an optimized estimation of secular trends over Antarctica. GRACE Oceanic Applications It has been shown by various authors that GRACE gravity field time series also trace mass-induced gravity variations over the oceans. For example, KANZOW et al. (2005) have intercompared global patterns of ocean mass signals based on early GRACE-only gravity field series provided by GFZ and CSR with in-situ ocean bottom pressure data from a ground truth site in the tropical northwest Atlantic Ocean and the ECCO ocean model. The study indicated a general agreement between these independent data sources but also showed remaining deficiencies in the GRACE data processing and suggested, among others, the substitution of the non-tidal barotropic ocean model by a baroclinic one. On a regional scale FENOGLIO-MARC et al. (2006) calculated mass variations in the Mediterranean Sea from analysis of hydrology corrected GRACE data and found reasonable agreement with altimetry-based estimates corrected for the steric part. LOMBARD et al. (2006) estimated steric sea level variations from a combined GRACE and Jason data analysis and found an overall good agreement. The net effect of the land water contribution to sea level change was estimated to be 0.19 ± 0.06 mm/yr which is comparable to the ice sheet contribution. VINOGRADOVA et al. (2007) investigated the relation between sea level and ocean bottom pressure and the vertical dependence of oceanic variability. Post Glacial Rebound and Ice Mass Loss Since 2003, absolute gravity measurements have been performed regularly by the Institute für Erdmessung Hannover in the Fennoscandian land uplift network covering Norway, Sweden, Finland and Denmark (TIMMEN et al. 2005, 2006). In cooperation with the national agencies and research institutions of the Nordic countries and BKG in Frankfurt, terrestrial absolute gravimetry is applied to observe the postglacial land uplift due to the isostatic adjustment of the crust. Nearly all absolute stations are colocated with continuously observing GPS stations. From the comparisons between the participating instruments, an overall accuracy of ±30 nm/s2 is indicated for a single absolute gravimeter and a single station determination. Thus, the gravity change due to the land uplift may be observed with an accuracy of ±10 to 20 nm/s² for a 5-year period. One purpose of these terrestrial in-situ observations is to validate the GRACE results (ground-truth) and first promising results have been presented in MÜLLER et al. (2003, 2005, 2007a, 2007b). In the same context, WIEHL et al. (2006) showed how the Baltic Sea water mass variations mask the postglacial rebound signal in CHAMP and GRACE gravity field solutions. Predicted changes in the geoid about Greenland to be used for GRACE validation have been described by FLEMING et al. (2005). SASGEN et al. (2005) described signatures of glacial changes in Antarctica, namely rates of geoid height change and radial displacement due to present and past ice mass variations. These are more or less due to changing ice mass balance and ice dynamics and shall be detectable by
F. Flechtner, T. Gruber, R. Schmidt: Gravity Field Satellite Missions 67 modern gravity space missions (FLURY, 2005). In SASGEN et al. (2007) secular trends in the geoid over Antarctica from the most recent GRACE gravity time series and geophysical models are evaluated and optimally combined by means of Wiener filtering. The results there indicate the improved quality but also homogeneity of the augmented GRACE gravity field series provided by different centres (including GFZ). References ABRIKOSOV O., JARECKI F., MÜLLER J., PETROVIC S., SCHWINTZER P.: The impact of temporal gravity variations on GOCE gravity field recovery; in: Observation of the System Earth from Space, Ed. Flury, Rummel, Reigber, Rothacher, Boedecker, Schreiber, Springer Verlag, 2006 BIANCALE R., BODE A.: Mean annual and seasonal atmospheric tide models based on 3-hourly and 6-hourly ECMWF surface pressure data; GFZ Scientific Technical Report STR06/01, GeoForschungsZentrum Potsdam, 2006 DOBSLAW H., THOMAS M.: Impact of river run-off on global ocean mass redistribution, Geophys., J. Int., doi: 10.1111/j. 1365-246X.2006.03247, 2006 FENGLER M., FREEDEN W., KOHLHAAS A., MICHEL V., PETERS TH.: Wavelet modelling of regional and temporal variations of the Earth's gravitational potential observed by GRACE; Schriften zur Funktionalanalysis und Geomathematik, Fachbereich Geomathematik, TU Kaiserslautern (Hrsg.), 2005, 21, 2005 FENGLER M., FREEDEN W., KOHLHAAS A., MICHEL V., PETERS TH.: Wavelet modeling of regional and temporal variations of the Earth's gravitational potential observed by GRACE; Journal of Geodesy, Vol. 81, p. 5-15, 2007 FENOGLIO-MARC L., KUSCHE J., BECKER M.: Mass variation in the Mediterranean Sea from GRACE and its validation by altimetry, steric and hydrologic fields. Geophysical Research Letters, 33:19606, doi:10.1029/2006GL026851, 2006 FLECHTNER F.: Short-term Atmosphere and Ocean Gravity Dealiasing for GRACE, In: Observation of the System Earth from Space: Status Seminar, Geotechnologien Science Report No. 3, Bavarian State Mapping Agency (BVLA), München, 2003 FLECHTNER F., SCHMIDT R., MEYER U.: De-aliasing of short-term atmospheric and oceanic mass variations for GRACE; in: Observation of the System Earth from Space, Ed. Flury, Rummel, Reigber, Rothacher, Boedecker, Schreiber, Springer Verlag, 2006 FLEMING K., MARTINEC Z., HAGEDORN J., WOLF D.: Contemporary changes in the geoid about Greenland: predictions relevant to gravity space missions. In C. Reigber, H. Lühr, P. Schwintzer, J. Wickert (editors), Earth observation with CHAMP: Results from Three Years in Orbit, pp. 217- 222, Springer Verlag, 2005 FLURY J., RUMMEL R.: Mass transport and mass distribution in the Earth system. Proceedings of Second International GOCE User Workshop "GOCE, The Geoid and Oceanography", ESA-ESRIN, Frascati, 8.-10. March 2004, Frascati, 2004 FLURY J.: Ice mass balance and ice dynamics from satellite gravity missions; Earth, Moon, and Planets, 2005, 94, 1-2, 85-94, 2005 GRUBER TH., PETERS TH.: Time variable gravity field: Using future Earth observing missions for high frequency dealiasing; Proceedings of IERS Workshop on Combination Research and Global Geophysical Fluids, Munich, IERS Technical Note No. 30, Ed. Richter, Verlag des Bundesamtes für Kartographie und Geodäsie, RFranfurt/Main, 2003 GÜNTNER A., SCHMIDT R., DÖLL P.: Supporting large-scale hydrogeological monitoring and modelling by time-variable gravity data. Hydrogeology Journal, 15(1), 167-170, doi: 10.1007/s10040-006-0089-1, 2007 HORWATH M., DIETRICH R.: Errors of regional mass variations inferred from GRACE monthly solutions; Geophysical Research Letters, Vol. 33, L07502, doi: 10.1029/2005GL 025550, 2006 HU X., SHI C., FLECTNER F., KÖNIG R., SCHWINTZER P., SCHMIDT R., MEYER U., MASSMANN F.H., REIGBER CH., ZHU S.: High frequency temporal Earth gravity variations detected by GRACE satellites; in: Observation of the System Earth from Space, Ed. Flury, Rummel, Reigber, Rothacher, Boedecker, Schreiber, Springer Verlag, 2006 ILK K.H., FLURY J., RUMMEL R., SCHWINTZER P., BOSCH W., HAAS C., SCHRÖTER J., STAMMER D., ZAHEL W., SCHMELING H., WOLF D., RIEGGER J., BARDOSSY A., GÜNTNER A.: Mass transport and mass distribution in the Earth system. Contributions of the new generation of satellite gravity and altimetry missions to the geosciences. Proposal for a German priority research program. GOCE-Projektbüro TU München, GeoForschungsZentrum Potsdam, München, Potsdam, 2004. ILK K.H., FLURY J., RUMMEL R., SCHWINTZER P., BOSCH W., HAAS C., SCHRÖTER J., STAMMER D., ZAHEL W., SCHMELING H., WOLF D., GÖTZE H.J., RIEGGER J., BARDOSSY A., GÜNTNER A., GRUBER TH.: Mass transport and mass distribution in the Earth system. Contributions of the new generation of satellite gravity and altimetry missions to the geosciences; Proposal for a German priority research program, 2nd edition. . GOCE-Projektbüro TU München, GeoForschungsZentrum Potsdam, München, Potsdam, 2005 JARECKI F., MÜLLER J.: Temporal gravity variations in GOCE gradiometric data; <strong>IAG</strong> Symposia Proceedings, Vol. 129, Ed. Jekeli, Bastos, Fernades, Springer Verlag, 2005 JARECKI F., MÜLLER J., PETROVIC S., SCHWINTZER P.: Temporal Gravity Variations in GOCE Gradiometric Data, In: Jekeli, C., Bastos, L., Fernandes, J. (eds.): Gravity, Geoid and Space Missions. pp. 333-338. Springer, Berlin Heidelberg New York 2005 KANZOW T., FLECHTNER F., CHAVE A., SCHWINTZER P., SCHMIDT R., SEND U.: Seasonal Variation of Ocean Bottom Pressure Derived from Grace: Local Validation and Global Patterns, Geophysical Research Letters, 110, C09001, Doi: 10.1029/2004 jc002772, 2005 KÖNIG R., REIGBER CH., ZHU S.Y.: Dynamic model orbits and Earth system parameters from combined GPS and LEO data, Advances in Space Research 36, pp. 431-437, doi 10.1016/j.asr.2005.03.064, 2005 KÖNIG R., SHI C., NEUMAYER K.H., ZHU S.: Conventional and New Approaches for Combining Multi-Satellite Techniques, in Flury J., Rummel R., Reigber C., Rothacher M., Boedecker G., Schreiber U. (Eds.), Observation of the Earth System from Space, pp. 413-424, Springer, Berlin, Heidelberg, 2006 KUSCHE J., SCHRAMA E.: Surface mass redistribution inversion from global GPS deformation and Gravity Recovery and Climate Experiment (GRACE) gravity data. Journal of Geophysical Research 110(B9): doi: 10.1029/2004 JB003556, 2005 Kusche J.: Approximate decorrelation and non-isotropic smoothing of time-variable GRACE-type gravity models, Journal of Geodesy, doi 10.1007/s00190-007-0143-0, 2007
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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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12 Commission 1 - Reference Frames
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14 Introduction Celestial Reference
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Page 26 and 27: 24 Introduction The contributions o
Page 30 and 31: 28 Satellite altimetry provides a p
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Page 44 and 45: 42 Commission 2 - Gravity Field sho
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
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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 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 and 94: M. Thomas, M. Soffel, H. Drewes: Ea
Page 95 and 96: 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
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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
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Permanent GNSS Networks, including
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G. Weber, M. Becker, J. Ihde: Perma
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G. Weber, M. Becker, J. Ihde: Perma
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General remarks The continuous and
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Introduction GNSS Based Sounding of
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J. Wickert, N. Jakowski: GNSS Based
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J. Wickert, N. Jakowski: GNSS Based
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References ADAM N.: TerraFirma Qual
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Introduction The period 2003 - 2007
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procedures and surveying instrument
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Motivation During the last years, n
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AVILA-RODRIGUEZ J.-A., PANY T., EIS
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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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