PRACTICAL APPLICATION OF CLOSE-RANGE PHOTOGRAM-METRY TO EXTRACTING GEOLOGICAL INFORMATION FROM TRENCH: TAKING THE MIAODIAN 4# LANDSLIDE AT THE SOUTHERN TABLELAND IN JINGYANG COUNTY AS AN EXAMPLE

doi:10.3969/j.issn.0253-4967.2020.05.014

Abstract

Abstract: Trench exposure is probably the most intuitive technological means of geology surveying work, and it is the key material to the right cognition of the delicate geological information. At the same time, trench is usually difficult to reserve, it needs to record the geological information of trench timely and accurately. The conventional methods of recording the delicate geological information of trenches are geology sketch and image mosaics technology, which mainly acquires the two-dimensional geological information. New data acquisition methods need to be explored for acquiring three-dimensional geological information. With the development of three-dimensional image technology, it is a new idea and method that terrestrial laser scanner and digital photogrammetry are applied to recording geological information of trenches.
This paper discusses the above problem by Miaodian 4^# landslide at the southern tableland in Jingyang County. The method of close-range photogrammetry to record the geological information is described as follows: 1)The photo-control-points on cleaned trench walls are established; 2)The photos from the surface of trench are collected by a Digital SLR Camera in the field. At the same time, measuring instrument can be used to measure the coordinates of the photo-control points; 3)The 3D model of the trench is reconstructed using the photogrammetric software(based on the processed photographs after the screening process and the coordinates of the photo-control points). In order to promote the application of this method, the paper also introduces the key technical problems of determining and setting up photo-control-points and scheme of photo acquisition. The 3D spatial data were acquired by methods described previously, which mainly include point cloud data, mesh, texture, orthomosaic, etc. The spatial resolution of the orthomosaic was 1.48mm/pix, and this high accuracy is enough to record millimeter-sized geological information. In order to verify the reliability of the results, the accuracy of close-range photogrammetry results is also verified and analyzed. The results show that the accuracy of close-range photogrammetry reached the centimeter level, and the level is close to the measurement equipment used in measuring the coordinates of photo-control-points. Therefore, the spatial resolution and accuracy of outcome data fully meet the requirements of recording the geological information.
Based on those 3D spatial data, the 2D and 3D geological applications of the data results were discussed in detail. First, the 2D geological application was discussed by taking the interpretation of trench profiles as an example. The technological processes mainly include creating orthomosaic, vectorization and interpretation. In the example, the interpretations of trench profiles were successfully completed using this method(Typically, the process of interpretation demands a combination of outdoor data recording and indoor experimental data). Specifically, the interpretations of small scale folds and thrust faults in the landslide deposit are obtained. Then, the 3D geological application was discussed by taking the data extraction of occurrence as an example. Extracting the feature points of 3D spatial data and computational method were described in detail. The occurrences of 3D model were contrasted to measurements of geological compass, and the two results are in good agreement. Based on the data of occurrence, they can be properly analyzed and further research can be developed from them. In this example, one can speculate about the forces and the motion state of the landslide after the data extraction of occurrence was synthesized and analyzed. And the results were normalized to the actual situation of the landslide.
Therefore, the 3D spatial data can be acquired quickly and accurately by extracting geological information from trench using close-range photogrammetry. Those outcome data include point cloud data, mesh, texture, orthomosaic, etc. The applications of those data could solve many complex engineering geological issues. Compared with the traditional methods, efficiency and security of field work are improved using photogrammetry technology, and it retains richer texture details than terrestrial laser scanning. Data results have traditional two-dimensional application functions. Moreover this data can achieve corresponding three-dimensional applications, which is deserved to be applied.

Key words: landslide, southern tableland in Jingyang County, trench, close-range photogrammetry, record of geological exploration, 3D model

摘要： 探槽是最直观的地质勘查技术手段之一, 也是正确认识地质体内部构造信息的关键资料。但探槽本身无法长久保存, 需要及时对探槽的地质数据进行精确记录和存储。传统的探槽地质信息记录方法主要有素描法和照片拼接技术, 通过其可获取探槽的二维地质信息。三维激光扫描和摄影测量技术等三维空间影像技术的发展, 为获取探槽的地质信息提供了全新的思路。文中以泾阳南塬庙店4^#滑坡探槽为例, 介绍了利用近景摄影测量技术记录探槽三维地质信息的方法。该方法首先在整理好的探槽表面布设像控点, 然后用数码单反相机采集探槽表面相片, 最后利用图像建模软件对探槽进行三维图像建模工作。为便于技术方法的推广应用, 文中还对像控点的测设和相片的采集方案等关键技术问题进行了详细介绍。为验证成果的可靠性, 还对近景摄影测量成果的精度进行了验证分析, 并在此基础上详细讨论了数据成果的二维和三维地质应用, 结果表明: 与传统方法相比, 利用摄影测量技术记录探槽的地质信息提高了野外工作的效率和安全性, 且该方法与三维激光扫描数据相比保留了更丰富的纹理细节; 数据成果在实现传统的平面应用功能的基础上, 还具有很好的三维应用价值, 值得推广应用。

关键词: 滑坡, 泾阳南塬, 探槽, 近景摄影测量, 地质信息获取, 三维模型

CLC Number:

P315.2

WEI Yong, XU Qiang, DONG Xiu-jun, GUO Peng, LI Song-lin, LI Hua-jin. PRACTICAL APPLICATION OF CLOSE-RANGE PHOTOGRAM-METRY TO EXTRACTING GEOLOGICAL INFORMATION FROM TRENCH: TAKING THE MIAODIAN 4^# LANDSLIDE AT THE SOUTHERN TABLELAND IN JINGYANG COUNTY AS AN EXAMPLE[J]. SEISMOLOGY AND GEOLOGY, 2020, 42(5): 1240-1254.

魏勇, 许强, 董秀军, 郭鹏, 李松林, 李骅锦. 近景摄影测量在探槽地质信息获取中的应用——以泾阳南塬庙店4^#滑坡为例[J]. 地震地质, 2020, 42(5): 1240-1254.

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