Experiences with the RTM Method in Local Quasi-Geoid Modeling
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 com...
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MDPI AG
2023-07-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/15/14/3594 |
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| author | Miao Lin Meng Yang Jianjun Zhu |
| author_facet | Miao Lin Meng Yang Jianjun Zhu |
| author_sort | Miao Lin |
| collection | DOAJ |
| description | 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 <i>r</i><sub>1</sub> for the inner zone and <i>r</i><sub>2</sub> 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 <i>r</i><sub>1</sub> and <i>r</i><sub>2</sub> 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 <i>r</i><sub>1</sub> and <i>r</i><sub>2</sub> 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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| spelling | doaj.art-137863dad5534f5aaec45d30e1a4b8b62023-11-18T21:13:00ZengMDPI AGRemote Sensing2072-42922023-07-011514359410.3390/rs15143594Experiences with the RTM Method in Local Quasi-Geoid ModelingMiao Lin0Meng Yang1Jianjun Zhu2College of Civil Engineering, Xiangtan University, Xiangtan 411105, ChinaSchool of Geospatial Engineering and Science, Sun Yat-sen University, Zhuhai 519082, ChinaSchool of Geosciences and Info-Physics, Central South University, Changsha 410083, ChinaIn 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 <i>r</i><sub>1</sub> for the inner zone and <i>r</i><sub>2</sub> 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 <i>r</i><sub>1</sub> and <i>r</i><sub>2</sub> 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 <i>r</i><sub>1</sub> and <i>r</i><sub>2</sub> 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.https://www.mdpi.com/2072-4292/15/14/3594residual terrain modelingdigital elevation modelreference topographyintegration radiuslocal quasi-geoid modeling |
| spellingShingle | Miao Lin Meng Yang Jianjun Zhu Experiences with the RTM Method in Local Quasi-Geoid Modeling Remote Sensing residual terrain modeling digital elevation model reference topography integration radius local quasi-geoid modeling |
| title | Experiences with the RTM Method in Local Quasi-Geoid Modeling |
| title_full | Experiences with the RTM Method in Local Quasi-Geoid Modeling |
| title_fullStr | Experiences with the RTM Method in Local Quasi-Geoid Modeling |
| title_full_unstemmed | Experiences with the RTM Method in Local Quasi-Geoid Modeling |
| title_short | Experiences with the RTM Method in Local Quasi-Geoid Modeling |
| title_sort | experiences with the rtm method in local quasi geoid modeling |
| topic | residual terrain modeling digital elevation model reference topography integration radius local quasi-geoid modeling |
| url | https://www.mdpi.com/2072-4292/15/14/3594 |
| work_keys_str_mv | AT miaolin experienceswiththertmmethodinlocalquasigeoidmodeling AT mengyang experienceswiththertmmethodinlocalquasigeoidmodeling AT jianjunzhu experienceswiththertmmethodinlocalquasigeoidmodeling |