Evaluation of the recent high-degree combined global gravity-field models for geoid modelling over Kenya
This study carries out an evaluation of the recent high-degree combined global gravity-field models (EGM2008, EIGEN-6C4, GECO and SGG-UGM-1) over Kenya. The evaluation is conducted using observed geoid undulations (18 data points, mainly in Nairobi area) and free-air gravity anomalies (8,690 data points, covering the whole country). All the four models are applied at full spherical harmonic degree expansion. The standard deviations of the differences between observed and GGMs implied geoid undulations at 18 GPS/levelling points over Nairobi area are ±11.62, ±11.48, ±12.51 and ±11.75 cm for EGM2008, EIGEN-6C4, GECO and SGG-UGM-1, respectively. On the other hand, standard deviations of the differences between observed and GGMs implied free-air gravity anomalies at 8,690 data points over Kenya are ±10.11, ±10.03, ±10.19 and ±10.00 mGal for EGM2008, EIGEN-6C4, GECO and SGG-UGM-1, respectively. These results indicate that the recent high-degree global gravity-field models generally perform at the same level over Kenya. However, EIGEN6C4 performs slightly better than EGM2008, GECO and SGG-UGM-1, considering the independent check provided by GPS/levelling data (admittedly over a small area). These results further indicate a good prospect for the development of a precise gravimetric geoid model over Kenya using EIGEN-6C4 by integrating local terrestrial gravity data in a removecompute-restore scheme.
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Cheng, M., & Ries, J. C. (2015). Evaluation of GOCE Gravity Models with SLR Orbit Tests. Newton’s Bulletin, 5, 187–192.
Förste, C., Bruinsma, S. L., Abrikosov, O., Lemoine, J.-M., Marty, J. C., Flechtner, F., Balmino, G., Barthelmes, F., & Biancale, R. (2014). EIGEN-6C4 the latest combined global gravity field model including GOCE data up to degree and order 2190 of GFZ Potsdam and GRGS Toulouse. GFZ Data Services. https://doi.org/10.5880/ICGEM.2015.1
Gachari, M. K., & Olliver, J. G. (1986). The detailed gravimetric geoid of Kenya. Survey Review, 28(221), 365–371. https://doi.org/10.1179/sre.19126.96.36.1995
Gachari, M. K., & Olliver, J. G. (1998). A high-resolution gravimetric geoid model of the Eastern Africa region. Survey Review, 34(269), 421–435. https://doi.org/10.1179/sre.1998.34.269.421
Gilardoni, M., Reguzzoni, M., & Sampietro, D. (2016). GECO: a global gravity model by locally combining GOCE data and EGM2008. Studia Geophysica et Geodaetica, 60, 228–247. https://doi.org/10.1007/s11200-015-1114-4
Godah, W., Krynski, J., & Szelachowska, M. (2015). On the accuracy assessment of the consecutive releases of GOCE-based GGMs over the area of Poland. Newton’s Bulletin, 5, 49–62.
Gomez, M. E., Perdomo, R., & Del Cogliano, D. (2017). Validation of recent geopotential models in Tierra Del Fuego. Acta Geophysica, 65, 931– 943. https://doi.org/10.1007/s11600-017-0085-y
Gruber, T., Visser, P. N. A. M., Ackermann, Ch., & Hosse, M. (2011). Validation of GOCE gravity field models by means of orbit residuals and geoid comparisons. Journal of Geodesy, 85, 845–860. https://doi.org/10.1007/s00190-011-0486-7
Heiskanen, W. A., & Moritz, H. (1967). Physical geodesy. Freeman, San Francisco. https://doi.org/10.1007/BF02525647
Hirt, C., Gruber, T., & Featherstone, W. E. (2011). Evaluation of the first GOCE static gravity field models using terrestrial gravity, vertical deflections and EGM2008 quasigeoid heights. Journal of Geodesy, 85, 723–740. https://doi.org/10.1007/s00190-011-0482-y
Huang, J., & Véronneau, M. (2015). Assessments of recent GRACE and GOCE release 5 global geopotential models in Canada. Newton’s Bulletin, 5, 127–148.
Kostelecký, J., Klokočník, J., Bucha, B., Bezděk, A., & Förste, C. (2015). Evaluation of the gravity field model EIGEN-6C4 in comparison with EGM2008 by means of various functions of the gravity potential and by GNSS/levelling. Geoinformatics FCE CTU, 14(1), 7–28. https://doi.org/10.14311/gi.14.1.1
Liang, W., Xu, X., Li, J., & Zhu, G. (2018). The determination of an ultra-high gravity field model SGG-UGM-1 by combining EGM2008 gravity anomaly and GOCE observation data. Acta Geodaetica et Cartographica Sinica, 47(4), 425–434.
Odera, P. A. (2016). Assessment of EGM2008 using GPS/levelling and free-air gravity anomalies over Nairobi County and its environs. South African Journal of Geomatics, 5(1), 17–30. https://doi.org/10.4314/sajg.v5i1.2
Odera, P. A. (2019). Assessment of the latest GOCE-based global gravity field models using height and free-air gravity anomalies over South Africa. Arabian Journal of Geosciences, 12(5), 1–7. https://doi.org/10.1007/s12517-019-4337-9
Odera, P. A., & Fukuda, Y. (2013). Towards an improvement of the geoid model in Japan by GOCE data: A case study of the Shikoku area. Earth, Planets and Space, 65(4), 361–366. https://doi.org/10.5047/eps.2012.07.005
Odera, P. A., & Fukuda, Y. (2017). Evaluation of GOCE-based global gravity field models over Japan after the full mission using free-air gravity anomalies and geoid undulations. Earth, Planets and Space, 69(135), 1–7. https://doi.org/10.1186/s40623-017-0716-1
Pavlis, N. K., Holmes, S. A., Kenyon, S. C., & Factor, J. K. (2012). The development and evaluation of the Earth Gravitational Model (EGM2008). Journal of Geophysical Research, 117(B4). https://doi.org/10.1029/2011JB008916
Rapp, R. H. (1971). Methods for the computation of geoid undulations from potential coefficients. Bulletin Géodésique, 101, 283–297. https://doi.org/10.1007/BF02521879
Rapp, R. H., Wang, Y. M., & Pavlis, N. K. (1991). The Ohio State 1991, Geopotential and Sea Surface topography harmonic coefficient models (Report 410). Department of Geodetic Science and Surveying, Ohio State University, USA.
Searle, R. C. (1970). A catalogue of gravity data from Kenya. Geophysical Journal of the Royal Astronomical Society, 19(5), 543–545. https://doi.org/10.1111/j.1365-246X.1970.tb00159.x
Swain, C. J., & Aftab Khan, M. (1977). A catalogue of gravity measurements in Kenya. Department of Geology, Leicester University, UK.
Swain, C. J., Aftab Khan, M. (1978). Gravity measurements in Kenya. Geophysical Journal of the Royal Astronomical Society, 53(2), 427–429. https://doi.org/10.1111/j.1365-246X.1978.tb03750.x
Swain, C. J. (1979). Gravity and seismic measurements in Kenya (PhD thesis). Department of Geology, Leicester University, UK.
Torge, W. (2001). Geodesy (3 ed.). de Gruyter. https://doi.org/10.1515/9783110879957
Wichiencharoen, C. (1982). FORTRAN programs for computing geoid undulations from potential coefficients and gravity anomalies (Internal report). Department of Geodetic Science and Surveying, The Ohio State University, Columbus, USA.