Gravity exploration terrain correction methods based on LiDAR-derived digital elevation model
QIU Longjun1,2, SUN Chengye1,2, YANG Yabin1,2, WU Xingang1,2
1. Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang, Hebei 065000, China; 2. National Center for Geological Exploration Technology, Langfang, Hebei 065000, China
Abstract：There are few references on terrestrial gravity near-and medium-zone terrains correction and their influencing factors based on LiDAR data systems.Previous accuracy evaluation related to terrain correction methods is based on the assumption of a mathematical model, and it can only discuss the influence of the elevation measurement errors on terrain correction and fails to analyze the errors generated by mathematical models such as a sectorial cone or sectorial cylinder.To this end, this paper employs the 1 m×1 m LiDAR elevation data from the U.S.Geological Survey three-dimensional elevation program (3DEP) and selects 12 data areas as research objects.Meanwhile, it adopts the calculation results of gravity analytical formulas of the rectangular prism model as the reference value of terrain correction and statistically compares the accuracy of previous mathematical models and calculation methods for near-and medium-zone terrain correction, which is the main innovation of this paper.On this basis, this paper analyzes the differences in the calculation methods and grid spacing in various terrains and compares the calculation efficiency of different methods.The results are as follows.①The correction range of the near-zone terrain and the computation model are the main factors affecting the calculation results, and the hybrid model can reduce the calculation error.When the correction radius of the near-zone terrain is 20 m, Scheme V can ensure that the average relative error of the 11 zones except the K zone is less than 20%.When the correction radius is 50 m, scheme VII can control the average relative error of all the zones below 13%, which indicates the highest calculation accuracy.②The maximum difference in the hill area with gently undulating terrain (Zone K) is comparable to that in the middle mountain (Zone J), and in the open pit copper mine zone with complex terrain (Zone L), the order of magnitude of the maximum difference for the seven schemes is nearly the same.③The correction formula for compensating angle terrain correction is not suitable for hilly areas, while the simplified formula for compensating angle terrain correction at the internal interface in the regional gravity survey specification has stronger applicability.④The medium-zone terrain correction is mainly affected by three factors, including the grid spacing of elevation data, the terrain correction range for the medium zone, and calculation methods, with the most important factor being the grid spacing.⑤By considering the calculation accuracy and calculation time, the mass line model method is the preferred choice for medium-zone terrain correction.
KUHN M, FEATHERSTONE W E, KIRBY J F.Complete spherical Bouguer gravity anomalies over Australia[J].Australian Journal of Earth Sciences, 2009, 56(2):213-223.
[2]
骆迪, 刘展, 李曼, 等.重力校正中存在的若干问题[J].地球物理学进展, 2013, 28(1):111-120.LUO Di, LIU Zhan, LI Man, et al.Several issues in gravity correction[J].Progress in Geophysics, 2013, 28(1):111-120.
[3]
孟庆奎, 舒晴, 高维, 等.一种用于重力场分离的约束插值切割方法[J].石油地球物理勘探, 2022, 57(5):1204-1217.MENG Qingkui, SHU Qing, GAO Wei, et al.A constrained interpolation cut method for gravity field separation[J].Oil Geophysical Prospecting, 2022, 57(5):1204-1217.
[4]
相鹏, 谭绍泉, 陈学国, 等.利用高斯径向基函数的拟神经网络重力反演方法[J].石油地球物理勘探, 2021, 56(6):1409-1418.XIANG Peng, TAN Shaoquan, CHEN Xueguo, et al.Gravity inversion method based on quasi-neural network featuring Gaussian radial basis function[J].Oil Geophysical Prospecting, 2021, 56(6):1409-1418.
[5]
HINZE W J.Bouguer reduction density, why 2.67[J].Geophysics, 2003, 68(5):1559-1560.
[6]
THOMAS G, KURT S, BERNHARD H.The rock water ice topographic gravity field model RWI_TOPO_2015 and its comparison to a conventional rock-equivalent version[J].Surveys in Geophysics, 2016, 37(5):937-976.
[7]
刘生荣, 高鹏, 耿涛, 等.不同源DEM数据在高山区重力中区地形改正中的适用性[J].物探与化探, 2019, 43(5):1111-1118.LIU Shengrong, GAO Peng, GENG Tao, et al.The applicability of different sources DEM data in median region terrain correction of gravity in high mountain areas[J].Geophysical & Geochemical Exploration, 2019, 43(5):1111-1118.
[8]
李志林, 朱庆, 谢潇.数字高程模型(第三版)[M].北京:科学出版社, 2018.
[9]
郭双建.机载激光雷达测量技术在大比例地形测绘中的运用及优势[J].世界有色金属, 2020, (8):214-215.GUO Shuangjian.Application and advantages of airborne Lidar measurement technology in large scale topographic mapping[J].World Nonferrous Metals, 2020, (8):214-215.
[10]
张俊, 张宝松, 邸兵叶, 等.高程数据网格间距对重力中区地形改正精度的影响[J].物探与化探, 2014, 38(1):157-161.ZHANG Jun, ZHANG Baosong, DI Bingye, et al.The effect of the grid spacing of elevation on the accuracy of median region terrain correction of gravity[J].Geophysical & Geochemical Exploration, 2014, 38(1):157-161.
黎哲君, 周冬瑞, 张毅, 等.基于DEM重力地形改正方法比较研究[J].海洋测绘, 2019, 39(1):1-6.LI Zhejun, ZHOU Dongrui, ZHANG Yi, et al.Comparative study on several DEM-based strategies for terrain reduction of gravity[J].Hydrographic Surveying and Charting, 2019, 39(1):1-6.
[13]
CALLAHAN D, BERBER M M.Vertical accuracy of the USGS 3DEP program data:study cases in Fresno County and in Davis, California[J].Boletim de Ciências Geodésicas, 2022, doi:10.1590/s1982-2170202200-0100004.
孙刚.重力勘探近区地形改正理论模型[J].煤田地质与勘探, 1993, 21(5):45-49.SUN Gang.Theoretical model of short range terrain correction of gravity exploration[J].Coal Geology & Exploration, 1993, 21(5):45-49.
[17]
夏江海.重力测量中地形改正的一个问题[J].石油物探, 1986, 25(2):81-86.XIA Jianghai.Problems concerning the terrain correction of gravity[J].Geophysical Prospecting for Petroleum, 1986, 25(2):81-86.
[18]
ZHOU X, ZHONG B, LI X.Gravimetric terrain corrections by triangular-element method[J].Geophysics, 1990, 55(2):232-238.
杨亚斌, 韩革命, 梁萌.重力近区地形改正精度探讨[J].物探化探计算技术, 2011, 33(1):92-96.YANG Yabin, HAN Geming, LIANG Meng.Gravity near zone terrain correction precision discussion[J].Computing Techniques for Geophysical and Geochemical Exploration, 2011, 33(1):92-96.
[21]
范祥发.区域重力调查近区地形改正快速计算[J].工程地球物理学报, 2007, 4(6):560-562.FAN Xiangfa.On fast calculation for the near region terrain correction of the regional gravity survey[J].Chinese Journal of Engineering Geophysics, 2007, 4(6):560-562.
