## 2 Materials and Methods
### High-Speed Videography and Motion Analysis  
High-speed videography and motion analysis is a widely used technique for the analysis of blast events. The process involves capturing a high-speed video of the blast event using specialized video cameras capable of recording at very-high frame rates. Typically, high-speed video (HSV) cameras have the capability to capture moving images with frame rates exceeding 250 frames per second (fps) [49]. The information obtained from high-speed video analysis can provide important insights into the behavior of the blast event monitored and can be used to optimize blasting designs and improve safety measures. High-speed motion analysis enables accurate identification of detonator timings, fragmentation, venting, fume generation, and flyrock [50; 51]. The captured video is then analyzed using motion analysis software (MAS) v.0.9.5 that allows for the measurement and analysis of various parameters and enables researchers and practitioners to gain a deeper understanding of the physics of blast events. MAS uses advanced image-processing algorithms to extract relevant information by transforming the image pixels into the desired real-world units. In this study, the flyrock fragments ejected from the blastholes were observed with a HSV camera, as shown in Figure 5, and recorded at a rate of 500 fps. For analysis of the recordings, an open-source MAS Kinovea v.0.9.5 was used.  
During motion analysis, it is desirable for the two-dimensional (2D) plane of motion to be orthogonal to the optical axis of the HSV camera. However, due to different spatial  
Figure 4: Research steps followed in this study.  
Figure 5: Observing and identifying a flyrock fragment being launched using an HSV camera.  
constraints at the mines regarding the location of the camera, ensuring orthogonality was not always possible. In such cases, to ensure minimal error in the measurements, the HSV scenes were calibrated using the 'plane-calibration' function in the MAS, which establishes a mapping between the pixels in an image and transforms the image coordinates to the corresponding real-world coordinates on a 2D plane and adjusts the pixels of the image using the calibrated coordinate system [15] as shown in Figure 6.  
For the measurement of flyrock velocity, all the visible flying fragments were identified, and their launch site, angle, and velocity were measured one by one by marking the positions of the fragment over successive frames for an initial trajectory path, as shown in Figure 7.  
Velocities measured on the initial trajectory path were averaged and noted as the \(v_{f}\) for that particular fragment. For determining the launch angle (\(\theta\)) an angle measurement tool in the MAS was used. Additionally, the distance reached by the flying fragments was measured with the help of geographical coordinates obtained from a hand-held GPS device which was used for validation of the danger zone prediction. To obtain a wider range of launch circumstances as the input for the modeling process [25], flyrock generated from 231 blastholes were recorded during the study, in which 79 full-scale bench blasts (with a total of 4110 blastholes) were monitored during the period 2018-2022.  
Figure 6: Perspective calibration of the scene carried out before motion analysis using an adjusted coordinate system.  
Figure 7: Measuring velocity and launch angle of an identified flying fragment over the initial trajectory.