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Point-Mass Gravity Field Modelling in the Perth Region

Point-Mass Gravity Field Modelling in the Perth Region. Sten Claessens Delft University of Technology, Department of Geodesy Will Featherstone Curtin University of Technology, Department of Spatial Sciences. Point-Mass Gravity Field Modelling in the Perth Region.

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Point-Mass Gravity Field Modelling in the Perth Region

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  1. Point-Mass Gravity Field Modelling in the Perth Region Sten Claessens Delft University of Technology, Department of Geodesy Will Featherstone Curtin University of Technology, Department of Spatial Sciences

  2. Point-Mass Gravity Field Modelling in the Perth Region 1. Occasion for the research 2. Aim of the research 3. Available data 4. Point-mass models 5. Approach for the research 6. Preliminary results 7. Summary and conclusions

  3. possible presence of distortions in the Australian Height Datum (AHD) • previous gravimetric geoid computations via Stokes’s integral were relatively unsuccessful Occasion for the research

  4. Construct a number of point masses in the Perth Region that fits the gravity measurements at the Earth’s surface Aim of the research (1)

  5. From these point masses, also generate a geoid model and then compare it to GPS-levelling to determine if: • The point-mass method is a suitable technique for modelling the geoid • Any systematic errors in the Australian Height Datum can reliably be detected Aim of the research (2)

  6. 2568 gravity measurements in the Perth Region from the Australian Geological Survey Organisation (AGSO) • 99 GPS-levelling points in the Perth Region • EGM96-geopotential model and altimeter data Available data

  7. Grid based models  Free positioned models • Free positioned point mass techniques adapt the distribution of the point masses to the geological situation • Free positioned point mass models do not need the use of a regular grid of gravity data Point-mass models

  8. 1. Computation of position Pmax with largest residual between point mass field and original data field 2. Iterative improvement of point mass position from start value under Pmax by non-linear optimisation 3. Iterative improvement of new point mass plus neighbouring point masses by non-linear optimisation Method of Barthelmes

  9. point mass geoid differences with GPS-levelling  negative mass disturbance  positive mass disturbance Preliminary results Statistics no. points = 99 min diff. = -0.331 m max diff. = 0.608 m mean diff. = 0.234 m std dev = 0.173 m

  10. 1. Point mass modelling is being used as an alternative for gravimetric geoid computations via Stokes’s integral 2. A free positioned point mass model is used because of: a. large density variations in the Perth Region b. non-homogeneous distribution of the gravity measurements 3. Any inconsistencies in the AHD cannot be detected yet because the STD of fit to GPS-levelling is too poor Summary and conclusions

  11. For providing software and assistance: • - Franz Barthelmes • GeoForschungsZentrum (GFZ), Potsdam, Germany • For providing data: • - Australian Geological Survey Organisation • - Western Australian Department of Land Administration • - Scripps Institute for Oceanography Acknowledgments

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