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Influence of DEM grid spacing and correction radius on terrain correction in gravity exploration |
ZHANG Fei-Fei1,2,3,4,5( ), WANG Wan-Yin1,2,3,7,8( ), LI Qian6, WANG Lin1,2,3, MA Jing1,2,3 |
1. Institute of Gravity and Magnetic Technology, Chang'an University, Xi'an 710054, China 2. School of Geology Engineering and Geomatics, Chang'an University, Xi'an 710054, China 3. Key Laboratory of Western China’s Mineral Resources and Geological Engineering Under Ministry of Education, Xi’an 710054, China 4. Key Laboratory of Gas Hydrate of Ministry of Natural Resources, Qingdao 266071, China 5. Qingdao Institute of Marine Geology, Qingdao 266071, China 6. Shanxi Provincial Institute of Geophysical and Geochemical Exploration, Yuncheng 044004, China 7. Key Laboratory of Marine Geology & Environment, CAS, Qingdao 266071, China 8. National Engineering Research Center of Offshore Oil and Gas Exploration, Beijing 100028, China |
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Abstract To remove the effect of terrain mass on observed gravity values, it is necessary to conduct terrain correction in gravity exploration. Terrains have the greatest impact on gravity values because they are the closest to observation points. However, the complex topographic relief makes it difficult to precisely determine the variation of topographic relief. Therefore, terrain correction is the most critical factor in the improvement of the precision of gravity exploration. The grid size of terrain data and the terrain correction radius are the key factors affecting the calculation precision of terrain correction. This study collected the DEM data with resolutions of 5 m, 10 m, 25 m, 50 m, and 100 m for plains, hills, and mountains. Based on these data, this study calculated conventional and generalized terrain correction values under different grid spacings and correction ranges and analyzed the influence of different grid spacings and correction radii on terrain correction in gravity exploration. The results are as follows: the gravity effect of the terrain mass above the geoid on the observation points was mainly concentrated in the range of 0~5 000 m and accounted for about 90% of the influence value of the total terrain mass. Attention should be paid to the correction of the middle and far areas during the terrain correction of hills and mountains, and it is necessary to appropriately increase the correction range of the middle areas; Different types of terrains had different requirements for grid spacings, and greater variations in topographic relief imposed higher requirements for the resolution DEM data. Based on the results of the comparative analysis, this study proposed some suggestions on the selection of DEM grid spacings and correction radii for different types of terrains. This study provides an important reference for the theoretical study and specification refinement of gravity terrain correction and has a great prospect for applications.
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Received: 21 September 2022
Published: 05 July 2023
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31] ">
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Schematic of traditional terrain correction[31]
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Schematic of generalized terrain correction
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Maps of different types terrain and slop
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Pie chart of the percentage of terrain correction values in different belt
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环带范围/m | 平原 | 丘陵 | 山地 | 传统地形校 正百分比/% | 广义地形校 正百分比/% | 传统地形校 正百分比/% | 广义地形校 正百分比/% | 传统地形校 正百分比/% | 广义地形校 正百分比/% | 0~20 | 78.76 | 2.00 | 33.27 | 2.35 | 20.41 | 1.17 | 20~50 | 3.64 | 3.27 | 5.44 | 4.12 | 11.76 | 3.34 | 50~100 | 1.29 | 5.23 | 2.94 | 6.59 | 8.01 | 6.30 | 100~200 | 0.68 | 9.56 | 2.65 | 11.61 | 7.78 | 11.78 | 200~500 | 0.47 | 22.11 | 4.19 | 24.05 | 11.30 | 25.34 | 500~1000 | 0.26 | 21.44 | 3.83 | 19.35 | 9.23 | 21.17 | 1000~1500 | 0.18 | 11.35 | 2.78 | 8.89 | 6.03 | 9.90 | 1500~2000 | 0.16 | 6.69 | 2.39 | 4.90 | 4.71 | 5.44 | 2000~3000 | 0.29 | 7.32 | 4.25 | 5.14 | 6.86 | 5.62 | 3000~5000 | 0.58 | 6.23 | 8.18 | 8.41 | 6.39 | 4.63 | 5000~10000 | 13.69 | 4.80 | 18.04 | 3.08 | 4.45 | 3.59 | 10000~15000 | | | 7.17 | 1.02 | 1.80 | 1.18 | 15000~20000 | | | 4.88 | 0.49 | 1.27 | 0.56 |
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The calculate results of the percentage of terrain correction values in different belt
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校正范围/m | 均方根误差/(10-5m·s-2) | 10 m网格 间距 | 25 m网格 间距 | 50 m网格 间距 | 100 m网格 间距 | 0~20 | 0.007620 | | | | 20~50 | 0.000203 | | | | 50~100 | 4.519×10-5 | 0.000136 | 0.00322 | | 100~200 | 1.463×10-5 | 5.120×10-5 | 9.626×10-5 | 0.000225 | 200~500 | 5.893×10-6 | 1.763×10-5 | 3.189×10-5 | 6.259×10-5 | 500~1000 | 3.545×10-6 | 5.549×10-6 | 9.136×10-6 | 1.187×10-6 | 1000~1500 | 3.020×10-6 | 3.617×10-6 | 4.429×10-6 | 5.065×10-6 | 1500~2000 | 3.980×10-7 | 8.788×10-7 | 1.502×10-6 | 1.906×10-6 | 2000~3000 | 4.337×10-7 | 8.955×10-7 | 1.522×10-6 | 1.777×10-6 | 3000~5000 | 3.374×10-7 | 7.228×10-7 | 1.575×10-6 | 1.402×10-6 | 5000~10000 | 4.326×10-6 | 1.290×10-5 | 3.627×10-5 | 7.842×10-5 |
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Compare of calculate result of terrain correction values based on different grid spacing (flat-land area)
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校正范围/m | 均方根误差/(10-5m·s-2) | 10 m网格 间距 | 25 m网格 间距 | 50 m网格 间距 | 100 m网格 间距 | 0~20 | 0.010451 | | | | 20~50 | 0.002317 | | | | 50~100 | 0.001187 | 0.007793 | 0.020051 | | 100~200 | 0.000566 | 0.003219 | 0.007084 | 0.015905 | 200~500 | 0.000335 | 0.001906 | 0.004584 | 0.009157 | 500~1000 | 9.210×10-5 | 0.000495 | 0.001205 | 0.002512 | 1000~1500 | 3.187×10-5 | 0.000156 | 0.000386 | 0.000798 | 1500~2000 | 1.754×10-5 | 7.771×10-5 | 0.000205 | 0.000424 | 2000~3000 | 2.100×10-5 | 8.392×10-5 | 0.00023 | 0.000517 | 3000~5000 | 2.113×10-5 | 9.799×10-5 | 0.000283 | 0.000652 | 5000~10000 | 1.555×10-5 | 8.894×10-5 | 0.000271 | 0.000645 | 10000~15000 | | | 6.301×10-5 | 0.000211 | 15000~20000 | | | 3.157×10-5 | 0.000112 |
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Compare of calculate result of terrain correction values based on different grid spacing (hill area)
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校正范围/m | 均方根误差/(10-5m·s-2) | 10 m网格 间距 | 25 m网格 间距 | 50 m网格 间距 | 100 m网格 间距 | 0~20 | 0.017771 | | | | 20~50 | 0.005265 | | | | 50~100 | 0.003399 | 0.010793 | 0.030051 | | 100~200 | 0.001998 | 0.009388 | 0.028690 | 0.076599 | 200~500 | 0.001272 | 0.007057 | 0.022021 | 0.060082 | 500~1000 | 0.000440 | 0.002757 | 0.008825 | 0.022756 | 1000~1500 | 0.000144 | 0.000938 | 0.00308 | 0.007950 | 1500~2000 | 7.145×10-5 | 0.000479 | 0.001569 | 0.003993 | 2000~3000 | 6.455×10-5 | 0.000467 | 0.001554 | 0.004041 | 3000~5000 | 4.704×10-5 | 0.000366 | 0.001178 | 0.003177 | 5000~10000 | 3.250×10-5 | 0.000257 | 0.000826 | 0.002251 | 10000~15000 | 1.183×10-5 | 8.595×10-5 | 0.000280 | 0.000784 | 15000~20000 | 4.650×10-6 | 3.406×10-5 | 0.000111 | 0.000312 |
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Compare of calculate result of terrain correction values based on different grid spacing (mountain area)
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Error analysis curves of terrain correction values based on different grid spacing (hill area)
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Error analysis curves of terrain correction values based on different grid spacing (mountain area)
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