Three‐dimensional (3D) documenting and rubbing of rock art is aimed to produce descriptive and analytic graphic documentation with metric scale and geospatial information for archaeological analysis. Although the integrated surveying technologies of aerial photogrammetry, close‐range photogrammetry, and laser scanning have been widely used to generate the 3D models of archaeological sites, the implementation of these technologies in complex surroundings with steep terrain, such as riverside cliffs, remains challenging. In this study, we present an unmanned aerial vehicle (UAV)‐based structure‐from‐motion (SfM) photogrammetry approach to obtain the 3D geospatial data of rock paintings. A field data collection approach for high‐resolution multiperspective images using UAV equipped with a high‐resolution camera is implemented together with high accuracy ground control points (GCPs). An appropriate flowchart of multi‐view stereo (MVS) photogrammetry processing is designed including multi‐view dense matching, bundle adjustment (BA) and metric rectification for the orthoimages production of the rock paintings. A digital rubbing approach based on the orthoimages is proposed to obtain the geometry contents, including symbols and characters, of the rock paintings. The Huashan rock paintings, which are located on the vertical faces of the cliffs that line the course of Zuo River, is taken as a case study. Our proposed approach can obtain orthoimages of the Huashan rock paintings with 2 mm resolution. The reality‐based 3D model can reach the absolute accuracy of 5 mm. Clear, exact, and blur‐free metric rubbing images of the Huashan rock paintings are produced, which are useful for the research and preservation of Zhuang culture.

中文翻译：

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左河谷岩画的三维文件记录和数字摩擦的无人驾驶飞机和结构运动摄影测量法

岩石艺术的三维（3D）记录和摩擦旨在产生具有公制比例和地理空间信息的描述性和分析性图形文件，以进行考古分析。尽管已经广泛使用了航空摄影测量，近距离摄影测量和激光扫描的综合测量技术来生成考古遗址的3D模型，但是在地形陡峭的复杂环境（如河边悬崖）中实施这些技术仍然具有挑战性。在这项研究中，我们提出了一种基于无人机（UAV）的结构自运动（SfM）摄影测量方法，以获取岩画的3D地理空间数据。使用配备有高分辨率相机的无人机对高分辨率多视角图像进行现场数据收集，并与高精度地面控制点（GCP）一起实施。设计了适合于多视图立体（MVS）摄影测量的流程图，包括多视图密集匹配，束调整（BA）和度量校正，用于岩画的正射影像生成。提出了一种基于正射影像的数字摩擦方法，以获取岩画的几何内容，包括符号和字符。以花山岩画为例，它们位于左河沿线的悬崖垂直面上。我们提出的方法可以获取2 mm分辨率的华山岩画的正像。基于现实的3D模型可以达到5毫米的绝对精度。制作出清晰，准确，无模糊的华山岩画，这对壮族文化的研究和保存很有用。