Wyniki wyszukiwania - BazTech

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Accuracy assessment of high and ultra high-resolution combined GGMs, and recent satellite-only GGMs - Case studies of Poland and Ethiopia

Godah Walyeldeen, Szelachowska Małgorzata, Gedamu Andenet A.

Reports on Geodesy and Geoinformatics

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2024

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Vol. 117

38--44

EN

The launch of dedicated satellite gravity missions (CHAMP, GRACE, GOCE, and GRACE-FO), as well as the availability of gravity data from satellite altimetry and terrestrial/airborne gravity measurements have led to a growing number of Global Geopotential Models (GGMs) developed. Thus, the evaluation of GGMs is necessary to ensure their accuracy in recovering the Earth's gravity field on local, regional, and global scales. The main objective of this research is to assess the accuracy of recent GGMs over Poland in Central Europe and Ethiopia in East Africa. Combined GGMs of high (degree and order (d/o) 2190) and ultra high-resolution (d/o 5540) as well as five satellite-only GGMs were evaluated using gravity data from absolute gravity measurements and airborne gravity surveys over Poland and Ethiopia, respectively. Based on this evaluation, the estimated accuracy of the high-resolution combined GGM is at the level of 2 mGal. The estimated accuracy for the ultra-high-resolution combined GGM is ~2.5 times lower. The satellite-only GGMs investigated recover the gravity signal at an accuracy level of 10 mGal and 26 mGal, for the areas of Poland and Ethiopia, respectively. When compensating for the omitted gravity signal using a high-resolution combined GGM and the topography model, an accuracy of 2 mGal can be achieved.

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Evaluation of GGMs based on the terrestrial gravity disturbance and Moho depth in Afar, Ethiopia

Alemu Eyasu

Artificial Satellites : Journal of Planetary Geodesy

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2021

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Vol. 56, No. 3

78--100

EN

To estimate Moho depth, geoid, gravity anomaly, and other geopotential functionals, gravity data is needed. But, gravity survey was not collected in equal distribution in Ethiopia, as the data forming part of the survey were mainly collected on accessible roads. To determine accurate Moho depth using Global Gravity Models (GGMs) for the study area, evaluation of GGMs is needed based on the available terrestrial gravity data. Moho depth lies between 28 km and 32 km in Afar. Gravity disturbances (GDs) were calculated for the terrestrial gravity data and the recent GGMs for the study area. The model-based GDs were compared with the corresponding GD obtained from the terrestrial gravity data and their differences in terms of statistical comparison parameters for determining the best fit GGM at a local scale in Afar. The largest standard deviation (SD) (36.10 mGal) and root mean square error (RMSE) (39.00 mGal) for residual GD and the lowest correlation with the terrestrial gravity (0.61 mGal) were obtained by the satellite-only model (GO_CONS_GCF_2_DIR_R6). The next largest SD (21.27 mGal) and RMSE (25.65 mGal) for residual GD were obtained by the combined gravity model (XGM2019e_2159), which indicates that it is not the best fit model for the study area as compared with the other two GGMs. In general, the result showed that the combined models are more useful tools for modeling the gravity field in Afar than the satellite-only GGMs. But, the study clearly revealed that for the study area, the best model in comparison with the others is the EGM2008, while the second best model is the EIGEN6C4.

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Roughness of three types of gravity disturbances and their correlation with topography in rugged mountains and flat regions

Tenzer R., Vajda P., Hamayun H.

Acta Geophysica

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2009

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Vol. 57, no. 3

657-679

EN

We investigate the roughness of and the correlation with topography of the observed, topographically corrected (T), and bathymetrically and topographically corrected (BT) gravity disturbances. The numerical investigation is carried out for the gravity disturbances at the Earth's surface and for the upward continued gravity disturbances at different altitudes. The area of study comprises a rough part of the Canadian Rockies surrounded by flat regions. The smoothest at the Earth's surface are the BT gravity disturbances. The evolution of roughness with altitude shows an interesting phenomenon, diverse for the three types of gravity disturbances. The correlation with topography over the study area of the observed gravity disturbances is bellow 0.6, and of the BT gravity disturbances approximately -0.6. The largest absolute value, of about -0.75, is found between the topography and the T gravity disturbances. This large negative correlation indicates a presence of the isostatic compensation in mountainous regions of the Canadian west coast.