Gravity Field Imaging by Continued Fraction Downward Continuation: A Case Study of the Nechako Basin (Canada)

The paper describes a whole-field imaging sensor developed on the principles of photoelasticity. The sensor produces colored fringe patterns when load is applied on the contacting surface. These fringes can be analyzed using conventional photoelastic techniques, however, as the loading in the present case is not conventional some new strategies need to be devised to analyze the load imprint. The loading is unconventional in the sense that low modulus photoelastic material is deformed under vertical load in the direction of light travel to induce the photoelastic effect. The paper discusses the efficacy of both RGB calibration and phase shifting techniques in sensing applications. The characteristics of fringe patterns obtained under vertical and shear loads have been studied and the results obtained under these conditions are discussed with their limitations specifically when this is applied for sensing applications. Finally a case study has been conducted to analyze a foot image and conclusions drawn from this have been presented.

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Regional Recovery of Gravity Anomaly from the Inversion of Diagonal Components of GOCE Gravitational Tensor: A Case Study in Ethiopia

Artificial Satellites ◽

10.2478/arsa-2018-0006 ◽

2018 ◽

Vol 53 (2) ◽

pp. 55-74 ◽

Cited By ~ 1

Author(s):

Mehdi Eshagh ◽

Andenet A. Gedamu ◽

Tulu B. Bedada

Keyword(s):

Gravity Anomaly ◽

Gravity Field ◽

Ocean Circulation ◽

Opposite Sign ◽

Joint Inversion ◽

Gravity Anomalies ◽

The Earth ◽

Tikhonov Regularisation ◽

The Difference

Abstract The tensor of gravitation is traceless as the gravitational field of the Earth is harmonic outside the Earth’s surface. Therefore, summation of the 2nd-order horizontal derivatives on its diagonal components should be equal to the radial one but with the opposite sign. The gravity field can be recovered locally from either of them, or even their combination. Here, we use the in-orbit diagonal components of the gravitational tensor measured by the gravity field and steady state ocean circulation explorer (GOCE) mission for recovering gravity anomaly with a resolution of 1°×1° at sea level in Ethiopia. In order to solve the system of equations, derived after discretisation of integral equations, the Tikhonov regularisation is applied and the bias of this regularisation is estimated and removed from the estimated gravity anomalies. The errors of the anomalies are estimated and their significance of recovery from these diagonal components is investigated. Statistically, the difference between the recovered anomalies from each scenario is not significant comparing to their errors. However, their joint inversion of the diagonal components improved the solution by about 1 mGal. Furthermore, the inversion processes are better stabilised when using errors of the input data compared with its exclusion, but at the penalty of degradation in accuracy of the estimates.

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Depth estimation of potential field by using a new downward continuation based on the continued fraction in space domain

Earth and Space Science ◽

10.1029/2021ea001789 ◽

2021 ◽

Author(s):

Wenna Zhou ◽

Chong Zhang ◽

Dailei Zhang

Keyword(s):

Potential Field ◽

Continued Fraction ◽

Depth Estimation ◽

Downward Continuation ◽

Space Domain

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Investigating the optimal integration of airborne, ship-borne, satellite and terrestrial gravity data for use in geoid determination

10.26686/wgtn.17018738 ◽

2021 ◽

Author(s):

◽

Rachelle Winefield

Keyword(s):

Least Squares ◽

Gravity Field ◽

Integration Method ◽

Bouguer Anomaly ◽

Least Squares Collocation ◽

Integration Methods ◽

Case Study Area ◽

Gravity Observation ◽

Gravity Map

<p>Each gravity observation technique has different parameters and contributes to different pieces of the gravity spectrum. This means that no one gravity dataset is able to model the Earth’s gravity field completely and the best gravity map is one derived from many sources. Therefore, one of the challenges in gravity field modelling is combining multiple types of heterogeneous gravity datasets. The aim of this study is to determine the optimal method to produce a single gravity map of the Canterbury case study area, for the purposes of use in geoid modelling. This objective is realised through the identification and application of a four-step integration process: purpose, data, combination and assessment. This includes the evaluation of three integration methods: natural neighbour, ordinary kriging and least squares collocation. As geoid modelling requires the combination of gravity datasets collected at various altitudes, it is beneficial to be able to combine the dataset using an integration method which operates in a three-dimensional space. Of the three integration methods assessed, least squares collocation is the only integration method which is able to perform this type of reduction. The resulting product is a Bouguer anomaly map of the Canterbury case study area, which combines satellite altimetry, terrestrial, ship-borne, airborne, and satellite gravimetry using least squares collocation.</p>

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