On the selection of optimal global geopotential model for geoid modeling: A case study in Pakistan

Abstract A statistical comparison has been made between gravity field parameters derived from different global geopotential models (GGMs) and observed gravity anomalies, gravimetric geoid and GPS-Leveling data. The motivation behind this study is the selection of best possible global geopotential model that best matches statistically with the local observed data in Pakistan. This will facilitate in decreasing the load on observed data for the development of regional gravimetric geoid in remove-compute-restore technique when used in the Stokes’s integral for computation of the residual part. It is observed that combined geopotential models such as EGM96 and PGM200A, EIGEN-GL04C and EIGEN-CG03C reflect the better match in the total spectral range of gravity and GPS-Leveling data. Results of the precise local geoid model also indicate similar characteristics. A very-high-degree model “EGM2008” (degree/order 2160) exhibits relatively superior statistical fit with observed ground data in Pakistan region. For satellite-only models an increasing trend in the standard deviation can be seen with maximum of about ∼4 m in difference between GPS-Leveling and corresponding GGM’s geoid with increase in the order from 50 to 120 and then it decreases afterwards. However, for the EIGEN-CHAMP03SP, standard deviation saturates to a value of 3.4 m. This is an indication of contamination in the long to medium wavelength part, i.e. 50–100° for the satellite-only models. Moreover, the models DEOS-CHAMP-01C, GGM02C and then ITG-GRACE03 appear to have better fit for medium to long wavelength and can possibly be recommended for use as long wavelength part with the local observed data. While a hybrid geopotential model selection can be achieved through the selection from either of DEOS-CHAMP-01C, GGM02C, GGM02S, EIGEN-GRACE02S or ITG-GRACE03 in the long wavelength (to degree and order 40) and EGM96, PGM200A, EIGEN-GL04C, EIGEN-CG03C or even EGM2008 in medium to short wavelength, i.e. from degree 41 to maximum degree and order.

[1]  Markus Rothacher,et al.  Towards an Integrated Global Geodetic Observing System , 2000 .

[2]  M. C. Lacy,et al.  Comparing recent geopotential models in Andalusia (Southern Spain) , 2006 .

[3]  C. C. Tscherning,et al.  The use of height data in gravity field approximation by collocation , 1981 .

[4]  L. Sjöberg,et al.  Reformulation of Stokes's theory for higher than second‐degree reference field and modification of integration kernels , 1991 .

[5]  N. K. Pavlis,et al.  The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential Model EGM96 , 1998 .

[6]  David E. Smith,et al.  The Development of the NASA GSFC and NIMA Joint Geopotential Model , 1997 .

[7]  W. Featherstone,et al.  Tests of the DMA/GSFC Geopotential Models over Australia , 1998 .

[8]  B. Heck.  An evaluation of some systematic error sources affecting terrestrial gravity anomalies , 1990 .

[9]  Pavel Ditmar,et al.  A technique for modeling the Earth’s gravity field on the basis of satellite accelerations , 2004 .

[10]  R. Rapp.  Use of potential coefficient models for geoid undulation determinations using a spherical harmonic representation of the height anomaly/geoid undulation difference , 1997 .

[11]  M. I. Yurkina,et al.  Methods for study of the external gravitational field and figure of the earth , 1962 .

[12]  Georgia Fotopoulos,et al.  Calibration of geoid error models via a combined adjustment of ellipsoidal, orthometric and gravimetric geoid height data , 2005 .

[13]  Richard H. Rapp,et al.  Closed Covariance Expressions for Gravity Anomalies, Geoid Undulations, and Deflections of the Vertical Implied by Anomaly Degree Variance Models. , 1974 .

[14]  R. Kiamehr,et al.  Comparison of the qualities of recent global and local gravimetric geoid models in Iran , 2005 .

[15]  Comparison of new Geoid Models and EIGEN-2S in the North Atlantic Region , 2005 .

[16]  M. Cheng,et al.  GGM02 – An improved Earth gravity field model from GRACE , 2005 .

[17]  R. Govind,et al.  Geiod evaluation in Australia—a status report , 1991 .

[18]  A Study of Zero-and first-degree terms in geopotential models over Australia , 1997 .

[19]  G. Balmino,et al.  Dedicated gravity field missions—principles and aims , 2002 .

[20]  A high resolution global gravity field model combining CHAMP and GRACE satellite mission and surface data: EIGEN-CG01C , 2006 .

[21]  Christoph Reigber,et al.  Status of the CHAMP Mission , 2000 .

[22]  C. Tscherning.  Geoid Determination by Least-square Collocation Using GRAVSOFT , 1994 .

[23]  U. Meyer,et al.  An Earth gravity field model complete to degree and order 150 from GRACE: EIGEN-GRACE02S , 2005 .