# Improvements in Rock Mass Description for Stope Design by Geophysical and Geochemical Methods
## 6 Photogrammetric Scanning for Rapid Geometrical Characterization
### Results and Discussion  
The results of tunnel digitization with a 360-degree camera are presented in Figure 10. Image acquisition with a 360-degree camera was three times faster than with a conventional  
Figure 11: Tunnel drift (**a**) digitized in this study using photogrammetry with a multi-camera rig (**b**) into a 3D model (**c**) that was mapped remotely, and four discontinuity planes were identified using manual, computer assisted, and semi-automatic methods (**d**) (modified after [52]). Figure 12: Slope 3D model (**a**) digitized in this study from UAV images captured in an underground mine, with four discontinuity sets (DS1-4) mapped remotely using a semi-automatic method (**b**), and their orientation plotted on a stereonet, with mean dip direction and dip angle (**c**). DSLR camera approach, and the workflow was easier and less prone to errors. The observations from the reconstructed 3D model matched the field measurements obtained using a conventional geological compass (Figure 10f). Some discrepancies were observed for sub-horizontal planes, which is a common issue reported in the literature. The results from the multi-camera data acquisition are presented in Figure 11c,d. The computer-assisted remote mapping method showed a mean difference of 8.3 and 2.4 degrees for dip direction and dip, respectively. The semi-automatic method resulted in a mean difference of 10.4 and 3.6 degrees for dip direction and dip, respectively (Figure 11d). The results obtained from remote mapping are comparable to reality, with mean differences within acceptable ranges for engineering applications. The results demonstrate the feasibility of using drone photogrammetry for remote fracture mapping in slopes, reducing data acquisition time and increasing safety by minimizing personnel exposure in hazardous areas. The most significant of these is the reduced data acquisition time. Drones enable rapid coverage of extensive areas, capturing high-quality images or videos necessary for detailed analysis, a task that would be considerably more time-consuming using traditional methods [53]. This aspect is crucial in dynamic underground environments where timely data are essential for decision-making. Another vital benefit is the increased safety that drone usage ensures. By minimizing the need for personnel to enter hazardous areas within slopes, the risk associated with geological hazards like rock falls or unstable ground is significantly reduced. This safety aspect is particularly critical in underground excavations where traditional access methods pose considerable risks. Drones offer coverage and accessibility, enabling the capture of images from otherwise difficult-to-reach areas. This capability ensures a more comprehensive mapping of discontinuities, contributing to a more accurate and deeper understanding of the rock mass. The the data obtained from UAV photogrammetry, as demonstrated in our study, were of a high resolution, allowing for precise mapping and analysis of the rock mass features required for stope design. However, there are limitations to this approach, including the high cost of specialized UAVs and their limited battery life. The cost factor associated with specialized drones is a significant barrier, particularly for smaller mining operations. Additionally, the limited battery life of drones restricts the duration of continuous data acquisition, which can be a hindrance in extensive underground excavations. The requirement for technical expertise in both operating drones and processing the acquired data is another consideration. The need for skilled personnel underscores the importance of training and development in this evolving technological field. Furthermore, the effectiveness of drones can be compromised by underground environmental conditions such as dust, moisture, and poor lighting, which can affect image quality and, consequently, the accuracy of photogrammetric models.