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| Terrain correction technology for airborne gamma-ray spectrometry based on DEM data |
XU Rui1,2( ), DENG Zhi-Peng1,2, WEN Long1,2, YU Peng1,2, LI Yuan-Dong1,2, GE Liang-Quan1,2() |
1. College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu 610059, China
2. Sichuan Provincial Key Laboratory of Geoscience and Nuclear Technology, Chengdu 610059, China |
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Abstract Aerial gamma spectroscopy measurement has important application value in mineral geological exploration, environmental radiation monitoring, and nuclear emergency response due to its advantages of high efficiency, flexibility, and avoidance of personnel radiation exposure risks. With the rapid development of drone technology, drones equipped with gamma-ray spectrometers have become a more flexible and cost-effective low altitude measurement method. However, drones typically fly at low altitudes below 40 meters, and complex terrain can significantly affect the solid angles of detection and the attenuation of gamma rays in the air, thereby reducing the accuracy of measurement results. This article proposes a terrain correction method for unmanned aerial vehicle (UAV) gamma spectroscopy measurement based on digital elevation model (DEM) data, targeting typical complex terrains such as mining pits, stepped mining faces, ore piles, and waste rock piles in open-pit rare earth mines. By establishing a micro element detection factor model and combining it with finite element discretization algorithm, quantitative correction of terrain undulations in the detection area can be achieved. The Monte Carlo simulation and field measurement results show that this method can effectively control the gamma ray intensity response error of terrain such as ridges, valleys, gentle slopes, and slopes within 10%, significantly improving the data quality of low altitude drone gamma spectrum measurement. The unmanned aerial vehicle (UAV) airborne gamma spectroscopy measurement in the open-pit mining area of rare earth mines shows that the relative error between the element content measured by UAV airborne gamma spectroscopy after terrain correction in the measurement area and the weighted average element content measured by surface gamma spectroscopy within 90% correction range is within 30% of the number of points, and the uranium content has increased from 53.2% without terrain correction to 74.3%; The thorium content has increased from 80.3% without terrain correction to 93.3%; The potassium content has increased from 94.7% without terrain correction to 97.2%. The terrain correction method has been verified to have strong practicality and reliability.
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Received: 28 September 2025
Published: 30 December 2025
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Corresponding Authors:
GE Liang-Quan
E-mail: 1853559753@qq.com;glq@cdut.edu.cn
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Schematic of the ground gamma ray intensity model for the point detector
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Relationship between detector height h and truncation distance Ltr within different correction ranges p @Energy=1 460 keV
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Schematic of terrain correction coefficient parameters for undulating terrain
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Five typical undulating terrain models
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Schematic of grid division (a) and topographic top view of MCNP (b)
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| 核素 | 40K | 214Bi | 208Tl | | 能量/ keV | 1460 | 1764 | 2614 | | 空气线衰减系数/cm-1 | 6.42×10-5 | 5.85×10-5 | 4.81×10-5 | | 地表介质线衰减系数/cm-1 | 8.11×10-2 | 7.45×10-2 | 6.24×10-2 |
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Linear attenuation coefficients for 40K (1 460 keV), 214Bi (1 764 keV), and 208Tl (2 614 keV) gamma rays in surface media and air
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| | 平坦地形 | 山脊地形 | 缓坡地形 | 斜坡地形 | 山谷地形 | | 地形校正前计数响应值 | 40K@1460 keV | 1.41×10-6 | 5.84×10-7 | 2.88×10-7 | 3.44×10-7 | 1.12×10-6 | | 214Bi@1764 keV | 1.32×10-6 | 5.68×10-7 | 2.98×10-7 | 3.14×10-7 | 9.44×10-7 | | 208Tl@2614 keV | 1.14×10-6 | 5.10×10-7 | 2.62×10-7 | 2.96×10-7 | 8.42×10-7 | | 5种地形上的Wf计算结果 | Wf(40K) | 4.86×10-3 | 2.11×10-3 | 1.07×10-3 | 1.25×10-3 | 3.71×10-3 | | Wf(214Bi) | 5.30×10-3 | 2.38×10-3 | 1.29×10-3 | 1.34×10-3 | 3.93×10-3 | | Wf(208Tl) | 6.33×10-3 | 2.93×10-3 | 1.55×10-3 | 1.69×10-3 | 4.70×10-3 | | 经地形校正后计数响应值 | 40K@1460 keV | 1.41×10-6 | 1.35×10-6 | 1.31×10-6 | 1.34×10-6 | 1.46×10-6 | | 214Bi@1764 keV | 1.32×10-6 | 1.26×10-6 | 1.22×10-6 | 1.24×10-6 | 1.27×10-6 | | 208Tl@2614 keV | 1.14×10-6 | 1.10×10-6 | 1.07×10-6 | 1.11×10-6 | 1.13×10-6 | | 地形校正后起伏地形计数响应值相对于平坦地形的相对误差/% | 40K@1460 keV | - | 4.74 | 7.36 | 5.28 | 3.72 | | 214Bi@1764 keV | - | 3.9 | 7.0 | 5.63 | 3.26 | | 208Tl@2614 keV | - | 3.35 | 6.14 | 2.75 | 0.53 |
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Monte Carlo simulated count rates before and after terrain correction, calculated detection factors Wf, and relative errors after correction for gamma rays from 40K (1 460 keV), 214Bi (1764 keV), and 208Tl (2 614 keV) over five types of terrain
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| 能窗 | 无人机航空伽马能谱测量 | 地面伽马能谱测量 | | 铀/10-6 | 钍/10-6 | 钾/% | 铀/10-6 | 钍/10-6 | 钾/% | | 测点数 | 509 | 509 | 509 | 309 | 309 | 309 | | 平均值 | 62.0 | 192.5 | 4.3 | 63.1 | 196.2 | 4.3 | | 均方差 | 45.3 | 92.3 | 0.2 | 55.4 | 113.1 | 0.6 |
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Statistical of uranium, thorium, and potassium contents from UAV-borne gamma-ray spectrometry and ground gamma-ray spectrometry surveys in the study area
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Terrain correction coefficients for the 40K (1 460 keV) (a), 214Bi (1 764 keV) (b), and 208Tl (2 614 keV) (c) energy windows of UAV-borne gamma-ray spectrometry at each sampling point
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DEM plan and ground point distribute of the survey area, terrain correction coefficient λ heatmap within 90% correction range at 40K(1 460 keV) of the survey area, and scatter plot with respect to relative height
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Original planar contour map of uranium element content in UAV, the planar contour map of element content after terrain correction, the planar contour map of element content measured by ground gamma spectroscopy, and the relative error distribution map of element content before and after terrain correction in UAV and the weighted average element content measured by ground gamma spectroscopy within 90% correction range
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Original planar contour map of thorium element content in UAV, the planar contour map of element content after terrain correction, the planar contour map of element content measured by ground gamma spectroscopy, and the relative error distribution map of element content before and after terrain correction in UAV and the weighted average element content measured by ground gamma spectroscopy within 90% correction range
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Original planar contour map of potassium element content in UAV, the planar contour map of element content after terrain correction, the planar contour map of element content measured by ground gamma spectroscopy, and the relative error distribution map of element content before and after terrain correction in UAV and the weighted average element content measured by ground gamma spectroscopy within 90% correction range
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