TGF: A New MATLAB-based Software for Terrain-related Gravity Field Calculations

Yang, Meng; Hirt, Christian; Pail, Roland

doi:10.3390/rs12071063

Cited by 18 publications

(4 citation statements)

References 38 publications

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“…The outer zone employs a DEM with a lower resolution and is defined by the integration radius r 2 (see the right panel of Figure 2). In some studies, more than two computation zones are selected [26][27][28]. In this study, we focus on the two-zone scheme, which has been implemented in the widely-used prism-based "tc.for" program in the GRAVSOFT software [29] and the recently developed tesseroid-based programs in the TCTESS software [30].…”

Section: Introductionmentioning

confidence: 99%

“…For more details about this approach, we refer to [32,33]. It should be noted that the RTM method utilizing the reference topography obtained from the SH approach has been successfully used for high-frequency GGM augmentation in many areas with different topographic regimes [26,28,[33][34][35]. In addition to the above-mentioned three approaches, the reference topography can also be obtained by applying a circular sharp cutoff filter [7] or a spherical Gaussian low-pass filter [36] to a high-resolution DEM.…”

Section: Introductionmentioning

confidence: 99%

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Experiences with the RTM Method in Local Quasi-Geoid Modeling

2023

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In local quasi-geoid modeling, the residual terrain modeling (RTM) method is often used to remove short-wavelength gravity field signals from the measured gravity on the ground in order to obtain a regularized and smooth gravity field that is suited for field interpolation and modeling. Accurate computation of RTM corrections plays a crucial role in computing an accurate local quasi-geoid, and it requires a set of fine-tuned parameters, including the combination of DEMs with different resolutions for suitably representing the real topography, the choice of integration radius for properly defining the extent of the computation zone, and the determination of reference topography to properly describe the RTM-reduced Earth’s surface. To our knowledge, this has not been systematically documented, despite its obvious importance. This study aims to systematically investigate the impact of these factors on RTM correction computation and, consequently, on local quasi-geoid modeling to provide practical guidelines for real-world applications. The tesseroid-based gravity forward modeling technique is employed to investigate the following issues existing in the practical use of the RTM method: ① Can the combination of a high-resolution DEM and a DEM with a lower resolution replace the single use of the high-resolution DEM for RTM correction computation while maintaining accuracy and improving efficiency? If it does, how do I properly choose the resolution of this coarse DEM as well as the integration radius r1 for the inner zone and r2 for the outer zone? ② How large would the differences between the RTM corrections computed by three types of reference topographies, which are obtained from the direct averaging (DA) approach, the moving averaging (MA) approach, and the spherical harmonic (SH) approach, be, and how large would their impact on quasi-geoid modeling be? To obtain objective findings, two research regions were selected for this investigation. One is the Colorado test area (USA) with rugged terrain, and the other is the Auvergne test area (France) with moderate terrain. The main numerical findings are: (1) the combination of the 3” resolution DEM (inner zone) and the 30″ resolution DEM (outer zone) is sufficient for accurate and efficient RTM correction computation; (2) if the resolution of the reference topography is 5′ or slightly lower, all three types of reference topographies are able to obtain local quasi-geoid models at a similar accuracy level, while the values of r1 and r2 are preferred to be at least 20 km and 111 km, respectively; (3) if the reference topography has a resolution of 30′ or lower, the MA or SH reference topography is recommended, especially for the latter one, and the values of r1 and r2 are suggested to be at least 20 km and 222 km, respectively. The above numerical findings can be taken as a reference for local quasi-geoid determination in areas with different topographic regimes than the two selected test areas.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experiences with the RTM Method in Local Quasi-Geoid Modeling

2023

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“…In gravimetric geophysics, these methods are used to compile Bouguer and mantle gravity maps [13][14][15][16][17][18]. Furthermore, numerous techniques have been developed and applied for a gravimetric interpretation of the Earth's inner structure [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

The Accuracy Assessment of Lithospheric Density Models

Tenzer,

Chen

2023

Applied Sciences

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The Earth’s synthetic gravitational and density models can be used to validate numerical procedures applied for global (or large-scale regional) gravimetric forward and inverse modeling. Since the Earth’s lithospheric structure is better constrained by tomographic surveys than a deep mantle, most existing 3D density models describe only a lithospheric density structure, while 1D density models are typically used to describe a deep mantle density structure below the lithosphere-asthenosphere boundary. The accuracy of currently available lithospheric density models is examined in this study. The error analysis is established to assess the accuracy of modeling the sub-lithospheric mantle geoid while focusing on the largest errors (according to our estimates) that are attributed to lithospheric thickness and lithospheric mantle density uncertainties. Since a forward modeling of the sub-lithospheric mantle geoid also comprises numerical procedures of adding and subtracting gravitational contributions of similar density structures, the error propagation is derived for actual rather than random errors (that are described by the Gauss’ error propagation law). Possible systematic errors then either lessen or sum up after applying particular corrections to a geoidal geometry that are attributed to individual lithospheric density structures (such as sediments) or density interfaces (such as a Moho density contrast). The analysis indicates that errors in modeling of the sub-lithospheric mantle geoid attributed to lithospheric thickness and lithospheric mantle density uncertainties could reach several hundreds of meters, particularly at locations with the largest lithospheric thickness under cratonic formations. This numerical finding is important for the calibration and further development of synthetic density models of which mass equals the Earth’s total mass (excluding the atmosphere). Consequently, the (long-to-medium wavelength) gravitational field generated by a synthetic density model should closely agree with the Earth’s gravitational field.

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“…However, the gravity field solutions are limited by the spatial distribution of terrestrial gravity measurements. Additionally, the method of extending the existing GGMs through the residual terrain modelling (RTM) technique is widely applied in the gravity field synthesis for areas requiring precise knowledge of the Earth's gravity field [48][49][50][51][52][53]. In this method, the high-frequency gravity field is generated by the residual masses between the Earth's topography and a smooth reference topography.…”

mentioning

confidence: 99%

Integration of Residual Terrain Modelling and the Equivalent Source Layer Method in Gravity Field Synthesis for Airborne Gravity Gradiometer Test Site Determination

Yang,

Li,

Feng

et al. 2023

Remote Sensing

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To calibrate airborne gravity gradiometers currently in development in China, it is urgent to build an airborne gravity gradiometer test site. The site’s selection depends on the preknowledge of high-resolution gravity and gradient structures. The residual terrain modelling (RTM) technique is generally applied to recover the short-scale gravity field signals. However, due to limitations in the quality and resolution of density models, RTM terrain generally assumes a constant density. This assumption can introduce significant errors in areas with substantial density anomalies and of reggued terrain, such as volcano areas. In this study, we promote a method to determine a high-resolution gravity field by integrating long-wavelength signals generated by EGM2008 with short-wavelength signals from terrain relief and shallow density anomalies. These short wavelength signals are recovered using the RTM technique with both constant density and density anomalies obtained through the equivalent source layer (ESL) method, utilizing sparse terrestrial gravity measurements. Compared to the recovery rate of 54.62% using the classical RTM method, the recovery rate increases to 86.22% after involving density anomalies. With this method, we investigate the gravity field signals over the Wudalianchi Volcano Field (WVF) both on the Earth’s surface and at a flight height of 100 m above the terrain. The contribution of each part and their attenuation characters are studied. In particular, the 5 km × 5 km area surrounding Bijiashan (BJS) and Wohushan (WHS) volcanos shows a strong gravity signature, making it a good candidate for the test site location. This study gives the location of the airborne gravity gradiometer test site which is an essential step in the instruments’ development. Furthermore, the method presented in this study offers a foundational framework for future data processing within the test site.

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TGF: A New MATLAB-based Software for Terrain-related Gravity Field Calculations

Cited by 18 publications

References 38 publications

Experiences with the RTM Method in Local Quasi-Geoid Modeling

Experiences with the RTM Method in Local Quasi-Geoid Modeling

The Accuracy Assessment of Lithospheric Density Models

Integration of Residual Terrain Modelling and the Equivalent Source Layer Method in Gravity Field Synthesis for Airborne Gravity Gradiometer Test Site Determination

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