Gravity Field Services coordinating global gravity field activities

Transcription

1 Gravity Field Services coordinating global gravity field activities Rene Forsberg National Space Institute (DTU-Space), Denmark Steve Kenyon National Geospatial-Intelligence Agency, USA

2 International Gravity Field Service The International Gravity Field Service (IGFS) is a unifying umbrella IAG service which: Coordinates collection, validation, archiving and dissemination of gravity field related data filling of global gravity data voids a priority Coordinates exchange of software for gravity field activities Coordinates courses, information materials and general public outreach relating to the Earth s gravity field Implements practical standards for general gravity field-related reference system issues, such as a global vertical datum Organize gravity field-related meetings (e.g., Fairbanks, 2010, next: Venice 2012) Represent gravity field pillar in GGOS Working groups on global absolute gravity network and geopotential model evaluations changing to

3 Structure of the IGFS International Gravimetric Bureau (BGI) Director S. Bonvalot, Toulouse International Geoid Service (IGeS) Director R. Barzaghi, Milano International Center for Earth Tides (ICET) Director J. P. Barriot, Tahiti International Center for Global Earth Models (ICGEM) Director J.Kusche, GFZ International DEM Service (IDEMS) Director P. Berry, De Mont Fort, UK Technical Centre of the IGFS S. Kenyon, NGA, US Central Bureau I. Marson and F. Coren, OGS, Trieste, Italy (start June 2011) Advisory Board Affiliate scientists Central Bureau OGS Technical Centre NGA BGI CNES Toulouse IGeS Polimi Milano ICET U. F. Polynesia ICGEM GFZ Potsdam IDEMS DeMontfort UK

4 Some service highlights: Global gravity models at ICGEM

5 Some service highlights (cont.) BGI: World gravity map project new global maps and data grids developed in geodetic-geophysical cooperation. Coordination of surveys. BGI database continues to expand and be QC ed.. but gravity still confidential or commercially restricted in too many regions IGES: Regional and continental geoid models, schools, Newton s Bulletin.. Last geoid School: St.Petersburg, June 2010 ICET: Earth-tide data base and coordination, need integration with Global Geodynamics Project superconducting gravimeter network IDEMS: Global DEMs for use in gravity field modelling and geodesy continue to improve: SRTM, ASTER, ACE-2, TerraSar Global DEM in 2014? NGA: EGM2008 spherical harmonic expansion to degree 2190 de-facto worldwide reference geoid and height system datum

6 Absolute Gravity Database BKG/BGI/NGA NGA

7 Combination of SG and AG

8 EGM2008

9 EGM2008 geoid commissioning errors

10 Need for coordinated surveys: Antarctica.. IAG/SCAR WG on Antarctica geoid (M. Scheinert) Time to fill southern GOCE gravity gap? AntGP data coverage British Antarctic Survey airborne Gravity (-2010) Univ.Texas/DTU-Space DC3 surveys and (blue: DTU; green: UTEX)

11 Gravity field products for GGOS Global gravity field models spherical harmonics consistent methodology satellite-only (n ~ 200), combination (n ~ 360 or 2160 or higher?) Time-varying gravity combination models Global vertical datum (6 mm ~10-9 ) EGM08 first realization Precise geoid models.. especially around key GGOS station sites Global absolute and superconducting gravity networks Network of globally distributed stations marked on the Earth body which are repeatedly observed with AG All stations include geometric sensors (permanent GNSS and others) Selected stations are equipped with an SG and provide the facilities for AG comparison Selected stations are equipped with tide gauges The registry (info and data) system relies upon the AG database New gravity reference system reaches the few µgal-level (IGSN71 replaced) Gravity field geodesy is alive and doing very well - GOCE, GRACE, absolute and airborne gravimetry global cm-geoid within reach - Satellite gravity => many more gravity users in cryosphere, oceanography, hydrology