Comparison of the qualities of recent global and local gravimetric geoid models in Iran
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A number of regional gravimetric geoid models have recently been determined for the Iran area, and a common problem is to select the best model, e.g. for engineering applications. A related problem is that in order to improve the local geoid models, the selection of the best Global Geopotential Model (GGM) model for the region is essential, to be used in a combined solution from GGM and local gravimetric data. We discuss these problems by taking advantage of 260 GPS/levelling points as an external tool for validation of different global and local geoid models in the absolute and relative senses. By using relative comparisons of the height differences between precise levelling and GPS/geoid models we avoid possible unknown systematic effects between the different types of observables.
The study shows that the combination of the newly released GRACE model (GGM02C) with EGM96 geoid model fits the GPS/levelling data in Iran with the best absolute and relative accuracy among the GGMs. Among the local geoid models, the newly gravimetric geoid model IRG04 agrees considerably better with GPS/levelling than any of the other recent local geoid models. Its rms fit with GPS/levelling is 55 cm. Hence, we strongly recommend the use of this new model in any surveying engineering or GPS/levelling projects in the area.
Keywordsgeoid GRACE GGM accuracy GPS/levelling
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- Abbolgasem A., 1994. Iranian Sea Surface Topography. M.Sc. Thesis, K.N. Toosi University, Tehran.Google Scholar
- Ardalan R. and Grafarend E., 2004. High Resolution geoid computation without applying Stokes’s formula case study: High resolution geoid of Iran. J. Geodesy, 78, 138–156.Google Scholar
- Fotopoulos G., 2003. An Analysis on the Optimal Combination of Geoid, Orthometric and Ellipsoidal Height Data. Ph.D. Thesis, University of Calgary, Canada.Google Scholar
- Heiskanen W.A. and Moritz H., 1967. Physical Geodesy, W. H. Freeman, San Francisco, USA.Google Scholar
- Hamesh M., 1991. Technical report about adjustment of Iranian first order levelling network. NCC J. Surveying, 1, 9–20.Google Scholar
- Hamesh M. and Zomorrodian H., 1992. Iranian gravimetric geoid determination. Second step. NCC J. Surveying, 6, 17–24, 52-63.Google Scholar
- Kirby J.F., Featherstone W.E. and Kearsley A.H.W., 1998. Tests of the DMA/GSFC geopotential models over Australia. International Geoid Service Bulletin, 7, 2–13.Google Scholar
- Lambeck K. and Coleman R., 1983. The Earth’s shape and gravity field: a report of progress from 1958 to 1982. Geophys. J. Royal Astron. Soc., 74, 25–54.Google Scholar
- Lemoine F.G., Smith D., Smith R., Kunz L., Pavlis E., Pavlis N., Klosko S., Chinn D., Torrence M., Williamson R., Cox C., Rachlin K., Wang Y., Kenyon S., Salman R., Trimmer R., Rapp R. and Nerem S., 1996. The development of the NASA GSFC and DMA joint geopotential model. Proc. Symp. on Gravity, Geoid and Marine Geodesy, Sept. 30–Oct. 5, 1996. The University of Tokyo, Tokyo, Japan.Google Scholar
- Najafi M., 2004. Determination of Precise geoid for Iran based on Stokes-Helmert Scheme. Report 2003, National Cartographic Center of Iran (NCC), TOTAK Project, Iran.Google Scholar
- Nahavandchi H., 2003. How to Compute a Precise Geoid and why it is important, Norwegian University of Science and Technology division of Geomatics (http://www.geoforum.no/pdf_filer/GH-2003_How_to_Compute_Precise_Geoid_and_Importance_Nahavandchi.pdf).Google Scholar
- Rapp R.H. and Pavlis N.K., 1990. The development and analysis of geopotential coefficients models to spherical harmonic degree 360. J. Geophys. Res., 95(B13), 21885–21911.Google Scholar
- Sjoberg L.E., 1987. The estimation of the power spectrum and reliability of models of the Earth’s gravity field by intercompariuson of independent models. Manuscr. Geod., 12, 104–112.Google Scholar
- Sjoberg L.E., 1991. Refined least squares modification of Stokes’s formula. Manuscr. Geod., 16, 367–375.Google Scholar
- Sjoberg L.E., 2003. A computational scheme to model the geoid by the modified Stokes formula without gravity reductions. J. Geodesy, 74, 255–268.Google Scholar
- Weber G. and Zomorrodian H., 1988. Regional geopotential model improvement for the regional Iranian geoid determination. Bulletin Geodesique, 62, 125–141.Google Scholar
- Wenzel G., 1985. Hochauflosende Kuglefunktionsmodelle fur das Gravitationspotential der Erde. Wissenschaftliche Arbeiten der Fachrichtung Vermessungswesen der Universitat Hannover Nr. 135.Google Scholar
- Wenzel H.G., 1998. Ultra-High Degree Geopotential Models GPM98A and GPM98B to Degree 1800. Report 98:4, Finnish Geodetic Institute, Masala, 71–80.Google Scholar