A comparison between sea-bottom gravity and satellite altimeter-derived gravity in coastal environments: A case study of the Gulf of Manfredonia (SW Adriatic Sea)

In this study, we present a comparative analysis between two types of gravity data used in geophysical applications: satellite altimeter-derived gravity and sea-bottom gravity.It is largely known that the marine gravity field derived from satellite altimetry in coastal areas is generally biased by signals back-scattered from the nearby land. As a result, the derived gravity anomalies are mostly unreliable for geophysical and geological interpretations of near-shore environments.To quantify the errors generated by the land-reflected signals and to verify the goodness of the geologic models inferred from gravity, we compared two different altimetry models with sea-bottom gravity measurements acquired along the Italian coasts from the early 50s to the late 80s.We focused on the Gulf of Manfredonia, located in the SE sector of the Adriatic Sea, where: (i) two different sea-bottom gravity surveys have been conducted over the years, (ii) the bathymetry is particularly flat, and (iii) seismic data revealed a prominent carbonate ridge covered by hundreds of meters of Oligocene-Quaternary sediments.Gravity field derivatives have been used to enhance both: (i) deep geological contacts, and (ii) coastal noise. The analyses outlined a &#8220;ringing-noise effect&#8221; which causes the altimeter signal degradation up to 17 km from the coast.Differences between the observed gravity and the gravity calculated from a geological model constrained by seismic, showed that all datasets register approximately the same patterns, associated with the Gondola Fault Zone, a major structural discontinuity traversing roughly E-W the investigated area.This study highlights the importance of implementing gravity anomalies derived from satellite-altimetry with high-resolution near-shore data, such as the sea-bottom gravity measurements available around the Italian coasts. Such analysis may have significant applications in studying the link between onshore and offshore geological structures in transitional areas.

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Application of Radial Basis Functions for Height Datum Unification

Geosciences ◽

10.3390/geosciences8100369 ◽

2018 ◽

Vol 8 (10) ◽

pp. 369 ◽

Cited By ~ 1

Author(s):

Ismael Foroughi ◽

Abdolreza Safari ◽

Pavel Novák ◽

Marcelo Santos

Keyword(s):

Gravity Field ◽

Satellite Altimetry ◽

Gravity Data ◽

Gravity Anomalies ◽

Basis Functions ◽

Gravity Potential ◽

Field Modelling ◽

Marine Gravity ◽

Local Gravity ◽

Local Gravity Field Modelling

Local gravity field modelling demands high-quality gravity data as well as an appropriate mathematical model. Particularly in coastal areas, there may be different types of gravity observations available, for instance, terrestrial, aerial, marine gravity, and satellite altimetry data. Thus, it is important to develop a proper tool to merge the different data types for local gravity field modelling and determination of the geoid. In this study, radial basis functions, as a commonly useful tool for gravity data integration, are employed to model the gravity potential field of the southern part of Iran using terrestrial gravity anomalies, gravity anomalies derived from re-tracked satellite altimetry, marine gravity anomalies, and gravity anomalies synthesized from an Earth gravity model. Reference GNSS/levelling (geometric) geoidal heights are used to evaluate the accuracy of the estimated local gravity field model. The gravimetric geoidal heights are in acceptable agreement with the geometric ones in terms of the standard deviation and the mean value which are 4.1 and 12 cm, respectively. Besides, the reference benchmark of the national first-order levelling network of Iran is located in the study area. The derived gravity model was used to compute the gravity potential difference at this point and then transformed into a height difference which results in the value of the shift of this benchmark with respect to the geoid. The estimated shift shows a good agreement with previously published studies.

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Coastal marine gravity modelling from satellite altimetry – case study in the Mediterranean

Journal of Geodetic Science ◽

10.1515/jogs-2020-0200 ◽

2021 ◽

Vol 11 (1) ◽

pp. 29-37

Author(s):

Adili Abulaitijiang ◽

Ole Baltazar Andersen ◽

Riccardo Barzaghi ◽

Per Knudsen

Keyword(s):

Gravity Field ◽

Satellite Altimetry ◽

Gravity Anomalies ◽

Gravity Modelling ◽

Coastal Marine ◽

Marine Gravity ◽

Collocation Technique ◽

Data Coverage ◽

Potential Improvement

Abstract The coastal marine gravity field is not well modelled due to poor data coverage. Recent satellite altimeters provide reliable altimetry observations near the coast, filling the gaps between the open ocean and land. We show the potential of recent satellite altimetry for the coastal marine gravity modelling using the least squares collocation technique. Gravity prediction error near the coast is better than 4 mGal. The modelled gravity anomalies are validated with sparse shipborne gravimetric measurements. We obtained 4.86 mGal precision when using the altimetry data with the best coastal coverage and retracked with narrow primary peak retracker. The predicted gravity field is an enhancement to EGM2008 over the coastal regions. The potential improvement in alti- metric marine gravity will be beneficial for the next generation of EGM development.

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Evaluation of Marine Gravity Anomaly Calculation Accuracy by Multi-Source Satellite Altimetry Data

Frontiers in Earth Science ◽

10.3389/feart.2021.730777 ◽

2021 ◽

Vol 9 ◽

Author(s):

Shanwei Liu ◽

Yinlong Li ◽

Qinting Sun ◽

Jianhua Wan ◽

Yue Jiao ◽

...

Keyword(s):

Root Mean Square Error ◽

Gravity Anomaly ◽

Mean Square Error ◽

Spatial Resolution ◽

Satellite Altimetry ◽

Gravity Anomalies ◽

Mean Square ◽

Altimetry Data ◽

Marine Gravity ◽

Satellite Altimetry Data

The purpose of this paper is to analyze the influence of satellite altimetry data accuracy on the marine gravity anomaly accuracy. The data of 12 altimetry satellites in the research area (5°N–23°N, 105°E–118°E) were selected. These data were classified into three groups: A, B, and C, according to the track density, the accuracy of the altimetry satellites, and the differences of self-crossover. Group A contains CryoSat-2, group B includes Geosat, ERS-1, ERS-2, and Envisat, and group C comprises T/P, Jason-1/2/3, HY-2A, SARAL, and Sentinel-3A. In Experiment I, the 5′×5′ marine gravity anomalies were obtained based on the data of groups A, B, and C, respectively. Compared with the shipborne gravity data, the root mean square error (RMSE) of groups A, B, and C was 4.59 mGal, 4.61 mGal, and 4.51 mGal, respectively. The results show that high-precision satellite altimetry data can improve the calculation accuracy of gravity anomaly, and the single satellite CryoSat-2 enables achieving the same effect of multi-satellite joint processing. In Experiment II, the 2′×2′ marine gravity anomalies were acquired based on the data of groups A, A + B, and A + C, respectively. The root mean square error of the above three groups was, respectively, 4.29 mGal, 4.30 mGal, and 4.21 mGal, and the outcomes show that when the spatial resolution is satisfied, adding redundant low-precision altimetry data will add pressure to the calculation of marine gravity anomalies and will not improve the accuracy. An effective combination of multi-satellite data can improve the accuracy and spatial resolution of the marine gravity anomaly inversion.

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Recovering Marine Gravity Over the Gulf of Guinea From Multi-Satellite Sea Surface Heights

Frontiers in Earth Science ◽

10.3389/feart.2021.700873 ◽

2021 ◽

Vol 9 ◽

Author(s):

Richard Fiifi Annan ◽

Xiaoyun Wan

Keyword(s):

Gravity Field ◽

Gravity Anomalies ◽

Sea Surface ◽

Shallow Waters ◽

Gulf Of Guinea ◽

Gravity Field Model ◽

The North ◽

Marine Gravity ◽

Sea Surface Heights ◽

East Component

A regional gravity field product, comprising vertical deflections and gravity anomalies, of the Gulf of Guinea (15°W to 5°E, 4°S to 4°N) has been developed from sea surface heights (SSH) of five altimetry missions. Though the remove-restore technique was adopted, the deflections of the vertical were computed directly from the SSH without the influence of a global geopotential model. The north-component of vertical deflections was more accurate than the east-component by almost three times. Analysis of results showed each satellite can contribute almost equally in resolving the north-component. This is attributable to the nearly northern inclinations of the various satellites. However, Cryosat-2, Jason-1/GM, and SARAL/AltiKa contributed the most in resolving the east-component. We attribute this to the superior spatial resolution of Cryosat-2, the lower inclination of Jason-1/GM, and the high range accuracy of the Ka-band of SARAL/AltiKa. Weights of 0.687 and 0.313 were, respectively, assigned to the north and east components in order to minimize their non-uniform accuracy effect on the resultant gravity anomaly model. Histogram of computed gravity anomalies compared well with those from renowned models: DTU13, SIOv28, and EGM2008. It averagely deviates from the reference models by −0.33 mGal. Further assessment was done by comparing it with a quadratically adjusted shipborne free-air gravity anomalies. After some data cleaning, observations in shallow waters, as well as some ship tracks were still unreliable. By excluding the observations in shallow waters, the derived gravity field model compares well in ocean depths deeper than 2,000 m.

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The gravity field over the Ungava Bay region from satellite altimetry and new land-based data: implications for the geology of the area

Canadian Journal of Earth Sciences ◽

10.1139/e98-085 ◽

1999 ◽

Vol 36 (1) ◽

pp. 75-89 ◽

Cited By ~ 4

Author(s):

Hamid Telmat ◽

Jean-Claude Mareschal ◽

Clément Gariépy

Keyword(s):

Satellite Altimetry ◽

Gravity Data ◽

Gravity Anomalies ◽

Gravity Models ◽

Crustal Thickening ◽

Seismic Line ◽

Crustal Thinning ◽

Gravity Measurements ◽

George River ◽

Superior Craton

Gravity data were obtained along two transects on the southern coast of Ungava Bay, which provide continuous gravity coverage between Leaf Bay and George River. The transects and the derived gravity profiles extend from the Superior craton to the Rae Province across the New Quebec Orogen (NQO). Interpretation of the transect along the southwestern coast of Ungava Bay suggests crustal thickening beneath the NQO and crustal thinning beneath the Kuujjuaq Terrane, east of the NQO. Two alternative interpretations are proposed for the transect along the southeastern coast of the bay. The first model shows crustal thickening beneath the George River Shear Zone (GRSZ) and two shallow bodies correlated with the northern extensions of the GRSZ and the De Pas batholith. The second model shows constant crustal thickness and bodies more deeply rooted than in the first model. The gravity models are consistent with the easterly dipping reflections imaged along a Lithoprobe seismic line crossing Ungava Bay and suggest westward thrusting of the Rae Province over the NQO. Because no gravity data have been collected in Ungava Bay, satellite altimetry data have been used as a means to fill the gap in data collected at sea. The satellite-derived gravity data and standard Bouguer gravity data were combined in a composite map for the Ungava Bay region. The new land-based gravity measurements were used to verify and calibrate the satellite data and to ensure that offshore gravity anomalies merge with those determined by the land surveys in a reasonable fashion. Three parallel east-west gravity profiles were extracted: across Ungava Bay (59.9°N), on the southern shore of the bay (58.5°N), and onshore ~200 km south of Ungava Bay (57.1°N). The gravity signature of some major structures, such as the GRSZ, can be identified on each profile.

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New Research on Gravity Field in Lithuanian Territory

Proccedings of 10th International Conference "Environmental Engineering" ◽

10.3846/enviro.2017.225 ◽

2017 ◽

Cited By ~ 1

Author(s):

Petras Petroškevicius ◽

Romuald Obuchovski ◽

Rosita Birvydienė ◽

Ricardas Kolosovskis ◽

Raimundas Putrimas ◽

...

Keyword(s):

Gravity Field ◽

Gravity Anomalies ◽

Satellite Geodesy ◽

Accuracy Estimation ◽

Coordinate Determination ◽

Improve Accuracy ◽

Gravity Measurements ◽

Normal Heights ◽

Rms Error ◽

New Research

New research of Lithuanian territory gravity field was started in 2016 with aim to improve accuracy of quasigeoid as well as accuracy of normal heights determined by methods of satellite geodesy. Obtained data could be used in the research of geophysics, geodynamics as well as in performing the precise navigation. Quartz automatic gravimeters Scintrex CG-5 are planned to be used for the survey consisting of 30000 points. Method of gravity measurements was worked out. RMS error of gravity determined with this method does not exceed 60 @Gal. Coordinates and heights of measured points are determined with GNSS using LitPOS network and LIT15G quasigeoid model. RMS error of coordinate determination does not exceed 0,20 m, for normal heights – 0,15 m. Method of gravity anomalies determination and their accuracy estimation was prepared.

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Effects of Interferometric Radar Altimeter Errors on Marine Gravity Field Inversion

Sensors ◽

10.3390/s20092465 ◽

2020 ◽

Vol 20 (9) ◽

pp. 2465

Author(s):

Xiaoyun Wan ◽

Shuanggen Jin ◽

Bo Liu ◽

Song Tian ◽

Weiya Kong ◽

...

Keyword(s):

Gravity Field ◽

Gravity Anomalies ◽

Ocean Surface ◽

Radar Altimeter ◽

The North ◽

Phase Errors ◽

Marine Gravity ◽

East Component ◽

The Impact ◽

Field Inversion

The traditional altimetry satellite, which is based on pulse-limited radar altimeter, only measures ocean surface heights along tracks; hence, leads to poorer accuracy in the east component of the vertical deflections compared to the north component, which in turn limits the final accuracy of the marine gravity field inversion. Wide-swath altimetry using radar interferometry can measure ocean surface heights in two dimensions and, thus, can be used to compute vertical deflections in an arbitrary direction with the same accuracy. This paper aims to investigate the impact of Interferometric Radar Altimeter (InRA) errors on gravity field inversion. The error propagation between gravity anomalies and InRA measurements is analyzed, and formulas of their relationship are given. By giving a group of possible InRA parameters, numerical simulations are conducted to analyze the accuracy of gravity anomaly inversion. The results show that the accuracy of the gravity anomalies is mainly influenced by the phase errors of InRA; and the errors of gravity anomalies have a linear approximation relationship with the phase errors. The results also show that the east component of the vertical deflections has almost the same accuracy as the north component.

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