Block stability analysis is important for studying the overall stability of surrounding rock in slope engineering. The main problem in regards to block stability analyses is determining the relative positional relationship between the structural plane and the free face. Consequently, studying the structural plane and free face is of great significance in engineering. By using the steep rocky slope of Shenxianju in Xianju County, Zhejiang Province as an example, this paper proposes new methods for determining the structural plane and free face using the coordinate projection method through an unmanned aerial vehicle. In addition, using MATLAB, the authors developed a CPG programme suitable for rock slope engineering and established a three-dimensional (3D) model of the slope allowing the visualisation of the structural plane, free face and slope characteristics. This practical engineering application demonstrates that this method is reliable and that the CPG programme is feasible. Overall, this study provides new technical means for landslide prediction and prevention and proposes an effective solution for efficient and safe operation in such instances.

块体稳定性分析对于研究边坡工程中围岩的整体稳定性很重要。关于砌块稳定性分析的主要问题是确定结构平面和自由面之间的相对位置关系。因此，研究结构平面和自由面在工程中具有重要意义。以浙江省仙居县神仙居陡峭的岩石边坡为例，提出了一种坐标投影法通过无人飞行器确定结构平面和自由面的新方法。此外，作者使用MATLAB开发了适用于岩石边坡工程的CPG程序，并建立了边坡的三维（3D）模型，从而可以可视化结构面，自由面和坡度特征。该实际工程应用证明该方法是可靠的，并且CPG程序是可行的。总体而言，这项研究为滑坡的预测和预防提供了新的技术手段，并提出了在这种情况下有效而安全地操作的有效解决方案。