Study of geoid–quasigeoid separation obtained from terrestrial gravity data and two geopotential models

2013 ◽  
Vol 7 (10) ◽  
pp. 4279-4290
Author(s):  
Mahmoud Mehramuz ◽  
Hossein Zomorrodian ◽  
Siamak Moazezi
Keyword(s):  
Gravity Data ◽  
Terrestrial Gravity ◽  
Geopotential Models

Accuracy Assessment of Recent High-Degree Global Geopotential Models Using Geodetic Control Points and Terrestrial Gravity Data in Turkey

2021 ◽  
Author(s):  
Muhammed Raşit Çevikalp ◽  
Bihter Erol ◽  
Bilal Mutlu ◽  
Serdar Erol
Keyword(s):  
Gravity Data ◽  
Geopotential Model ◽  
Geoid Model ◽  
Terrestrial Gravity ◽  
Practical Applications ◽  
Geopotential Models ◽  
Vertical Datum ◽  
Height System ◽  
Orthometric Heights ◽  
Height System Unification

<p>The maintenance of leveling benchmark is both laborious and costly due to distortions caused by geodynamic activities and local deformations. It is necessary to realize geoid-based vertical datum, which also enables calculation from ellipsoidal heights obtained from GNSS to orthometric heights that have physical meaning. It can be considered as an important step for height system unification as it eliminates the problems stem from the conventional vertical datum. The ongoing height modernization efforts in Turkey focus to improve quality and coverage of the gravity data, eliminate errors in existing terrestrial gravity measurements in order to achieve a precise geoid model. Accuracy of the geopotential model is crucial while realizing a geoid model based vertical datum as well as unifying the regional height systems with the International Heights Reference System. In this point of view, we assessed the accuracies of recently released global geopotential models including XGM2019e_2159, GECO, EIGEN-6C4, EGM2008, SGG-UGM-1, EIGEN-6C3stat, and EIGEN-6C2 using high order GNSS/leveling control benchmarks and terrestrial gravity data in Turkey. The reason for choosing these models in the validations is their relatively higher spatial resolutions and improved accuracies compared to other GGMs in published validation results with globally distributed terrestrial data. The GNSS/leveling data used in validations include high accuracy GNSS coordinates in ITRF datum with co-located Helmert orthometric heights in regional vertical datum. 100 benchmarks are homogeneously distributed in the country with the benchmarks along the coastlines. In addition, the terrestrial gravity anomalies with 5 arc-minute resolution were also used in the tests. In order to have comparable results, residual terrain effect has been restored to the GGM derived parameters. Numerical tests revealed significant differences in accuracies of the tested GGMs. The most accurate GGM has the comparable performance with official regional geoid model solutions in Turkey. The drawn results in the study were interpreted and discussed from practical applications and height system unification points in conclusion.</p>

scholarly journals ASSESSMENT OF RECENT GOCE-BASED GLOBAL GEOPOTENTIAL MODELS AND EGM2008 IN NIGER REPUBLIC

2019 ◽  
Vol 45 (3) ◽  
pp. 116-125
Author(s):  
Salissou Ibrahim Yahaya ◽  
Driss El Azzab
Keyword(s):  
Gravity Data ◽  
Geoid Height ◽  
Terrestrial Gravity ◽  
Terrain Model ◽  
Spectral Bands ◽  
Geopotential Models ◽  
Before And After ◽  
Gravity Database ◽  
Enhancement Method ◽  
The One

In this study, we assessed recent GOCE-based Global Geopotential Models (GGMs) and EGM2008 in Niger. The combined GGMs EIGEN_6C4, GECO and EGM2008 were evaluated up to their maximum degree and order (d/o) 2,190 to select the one for gravity database densification. The following pure satellite GGMs were assessed for the modelling of the long and medium wavelengths in geoid computation: GGM05G, ITU_GGC16, EIGEN_6S4v2 and the fifth releases from direct (DIR5), space-wise (SPW5) and time-wise (TIM5) approaches. The GGMs are compared to terrestrial gravity data and geoid heights from GNSS/Levelling points before and after applying spectral enhancement method (SEM) by residual terrain model (RTM) for combined models and by RTM and the coefficients of selected combined GGM for pure satellite models. The agreements of combined GGMs with terrestrial gravity data and GNSS/Levelling points, in terms of root mean square (RMS) are about 4.88 to 5.02 mGal and 0.14 to 0.16 m, respectively. EIGEN_6C4 was selected as it showed the best performance in terms of geoid height differences and the probability of 3-sigma rule for gravity anomaly differences. At d/o 200, DIR5 showed a good agreement with terrestrial gravity data (5.04 mGal) and GNSS/Levelling points (0.15 m) after applying SEM, it was then retained. All GOCE-based models exhibited a good performance in long and medium wavelengths confirming the good recovery of the gravity field by the spatial gravity mission in these spectral bands.

Local geoid model of the Western Desert in Egypt using terrestrial gravity data and global geopotential models

2021 ◽  
Vol 14 (15) ◽  
Author(s):  
Mostafa Ahmed Elwan ◽  
Ahmad Helaly ◽  
Khaled Zharan ◽  
Elsayed Issawy ◽  
Ahmed Abd El-Gawad
Keyword(s):  
Gravity Data ◽  
Western Desert ◽  
Geoid Model ◽  
Terrestrial Gravity ◽  
Geopotential Models ◽  
Local Geoid

scholarly journals An evaluation of recent GOCE geopotential models in Brazil

2012 ◽  
Vol 2 (2) ◽  
pp. 144-155 ◽  
Author(s):  
G. Guimarães ◽  
A. Matos ◽  
D. Blitzkow
Keyword(s):  
Steady State ◽  
Ocean Circulation ◽  
Gravity Data ◽  
The Other ◽  
Entire Area ◽  
Terrestrial Gravity ◽  
Terrain Model ◽  
Geopotential Models ◽  
Gravity Disturbances ◽  
Rms Errors

An evaluation of recent GOCE geopotential models in BrazilSeveral global geopotential models based on Gravity field and steady-state Ocean Circulation Explorer (GOCE) data have been published in the last two years. Some of these models use combinations of different satellite missions, while others use only GOCE data. This paper presents the evaluation and analysis of each approach using GOCE data in the Southeast of Brazil. Two assessments have been made. We compared the geoid heights derived from GOCE-based models with the geoidal heights from 176 GPS stations on leveling benchmarks. The findings show an improvement in GOCE-based models TIM_R3 (0.40 m) and DIR_R3 (0.39 m) for degree and order 210 in relation to EGM2008 (0.44 m) in terms of RMS. For the other models the results did not exceed 0.44 m. The second evaluation reports the comparison in terms of gravity disturbances between terrestrial gravity data and the models. The results, in terms of RMS and up to degree and order 210, indicate slightly low GOCO 02S values (10.34 mGal), TIM_R2 (10.37 mGal) and TIM_R3 (10.47 mGal) compared to EGM2008 (10.66 mGal). We also applied the residual terrain model and, as a result, the RMS errors were reduced by ~35% (~6.0 mGal) in the entire area and by ~45% in the mountain region.

scholarly journals Evaluation of recent Earth’s global gravity field models with terrestrial gravity data

2016 ◽  
Vol 46 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Alexander P. Karpik ◽  
Vadim F. Kanushin ◽  
Irina G. Ganagina ◽  
Denis N. Goldobin ◽  
Nikolay S. Kosarev ◽  
...  
Keyword(s):  
Gravity Anomaly ◽  
Gravity Field ◽  
Gravity Data ◽  
Rapid Development ◽  
Environmental Research ◽  
Statistical Characteristics ◽  
Terrestrial Gravity ◽  
Geopotential Models ◽  
Comparison Results ◽  
Gravity Field Models

Abstract In the context of the rapid development of environmental research technologies and techniques to solve scientific and practical problems in different fields of knowledge including geosciences, the study of Earth’s gravity field models is still important today. The results of gravity anomaly modelling calculated by the current geopotential models data were compared with the independent terrestrial gravity data for the two territories located in West Siberia and Kazakhstan. Statistical characteristics of comparison results for the models under study were obtained. The results of investigations show that about 70% of the differences between the gravity anomaly values calculated by recent global geopotential models and those observed at the points in flat areas are within ±10 mGal, in mountainous areas are within ±20 mGal.

scholarly journals Validation of recent GOCE/GRACE geopotential models over Khartoum state - Sudan

2012 ◽  
Vol 2 (2) ◽  
pp. 88-97 ◽  
Author(s):  
A. Abdalla ◽  
H. Fashir ◽  
A. Ali ◽  
D. Fairhead
Keyword(s):  
Gravity Field ◽  
Spherical Harmonics ◽  
Gravity Data ◽  
Target Area ◽  
Local Data ◽  
Combined Model ◽  
Terrestrial Gravity ◽  
Long Wavelength ◽  
Geopotential Models ◽  
Data Points

Validation of recent GOCE/GRACE geopotential models over Khartoum state - SudanThis paper evaluates a number of latest releases of GOCE/GRACE global geopotential models (GGMs) using the GPS-levelling geometric geoid heights, terrestrial gravity data and existing local gravimetric models. We investigate each global model at every 5 degree of spherical harmonics. Our analysis shows that the satellite-only models derived by space-wise and time-wise approaches (SPW_R1, SPW_R2 TIM_R1 and TIM_R2), GOCO01S together with EGM08 (combined model) are very distinct and consistent to the local data, which guarantees one of them to be selected as the best of candidate models and then to be utilized in our further geoid studies. One of Satellite-only models will be employed for acquiring the long wavelength geoid component which is one of major steps in the geoid determination. EGM08 will be used to compensate and restore the missing gravity data points in the un-surveyed parts within the target area. We expect further improvements in geoid studies in Sudan due to the improved medium wavelength part of the gravity field from GOCE mission.

scholarly journals DETERMINATION AND MAPPING OF THE TERRESTRIAL GRAVITY ANOMALIES IN THE MOUNTAINOUS AREAS OF IRAQ

2021 ◽  
Vol 6 (24) ◽  
pp. 213-225
Author(s):  
Shazad Jamal Jalal ◽  
Tajul Ariffin Musa ◽  
Ami Hassan Md Din ◽  
Wan Anom Wan Aris
Keyword(s):  
Gravity Data ◽  
Physical Geodesy ◽  
Gravity Anomalies ◽  
Gravity Survey ◽  
Mountainous Areas ◽  
Entire Study ◽  
Terrestrial Gravity ◽  
The Past ◽  
Regional Gravity ◽  
Entire Study Area

Gravity data and computing gravity anomalies are regarded as vital for both geophysics and physical geodesy fields. The mountainous areas of Iraq are characterized by the lack of regional gravity data because gravity surveys are rarely performed in the past four decades due to the Iraq-Iran war and the internal unstable political situation of this particular region. In addition, the formal map of the available terrestrial gravity which was published by the French Database of Bureau Gravimetrique International (International Gravimetric Bureau-in English) (BGI), introduces Iraq and the study area as a remote area and in white color because of the unavailability of gravity data. However, a dense and local (not regional) gravity data is available which was conducted by geophysics researchers 13 years ago. Therefore, the regional gravity survey of 160 gravity points was performed by the authors at an average 11 km apart, which was covers the whole area of Sulaymaniyah Governorate (part of the mountainous areas of Iraq). In spite of Although the risk of mine fields within the study area, suitable safe routes as well as a helicopter was used for the gravity survey of several points on the top of mountains. The survey was conducted via Lacoste and Romberg geodetic gravimeter and GPS handheld. The objective of the study is to determine and map the gravity anomalies for the entire study area, the data of which would assist different geosciences applications.

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