OFFICIAL excavation depths exceed hundreds of metres, the consequences of inadequate monitoring are amplified both in terms of safety and economic impact. The importance of geotechnical monitoring extends beyond hazard mitigation. Accurate deformation and stability data inform reliability-based design approaches, enabling engineers to quantify and propagate uncertainty through slope design models. This supports defensible acceptance criteria for inter-ramp and overall slope angles, optimising resource recovery while maintaining compliance with regulatory and corporate risk thresholds (Creighton et. al., 2022). Furthermore, monitoring data are increasingly leveraged for predictive analytics, feeding into digital twins and probabilistic simulations that enhance mine planning and operational resilience. A diverse range of technologies is available to meet these monitoring objectives, each with distinct capabilities and limitations (Sharon & Eberhardt, 2020). Radar-based slope monitoring systems have become ubiquitous in surface mining, offering sub-millimetre precision for line-of-sight (LOS) displacement measurements over large areas. Interferometric radars provide continuous coverage and rapid scan rates, making them indispensable for detecting accelerating movements indicative of impending failure. However, radar systems are inherently constrained by line-of-sight bias, which can obscure true deformation vectors and misrepresent failure mechanisms, particularly in complex geometries or oblique viewing scenarios (Elmouttie & Dean 2021). To address these limitations, research into vision-based monitoring technologies has shown promise. High-resolution cameras, often co-located with radar units, enable feature tracking across successive images, providing complementary displacement data in orthogonal directions. When integrated through sensor fusion algorithms, radar and vision systems can deliver three-dimensional deformation estimates, significantly improving interpretive accuracy for slope stability assessments (Elmouttie et. al., 2021). Beyond surface monitoring, geophysical sensing technologies extend surveillance into the subsurface. Borehole radar systems which facilitate structural mapping and look-ahead capabilities during drilling (Zhou et. al., 2020), while distributed fibre optic sensing (DFOS) offers continuous strain, temperature, and acoustic measurements along kilometres of low-cost optical fibre. DFOS has demonstrated utility in detecting microseismic activity, monitoring stress redistribution, and characterising rock mass behaviour and geological conditions in both open-pit and underground settings (Duan et. al., 2025a; Duan et al., 2025b). Recent advances in silicon photonics promise to reduce the cost and complexity of DFOS interrogators (Shekhar et al., 2024), accelerating adoption in large-scale mining operations. Emerging approaches now seek to integrate these modalities, namely radar, vision, and fibre optics, within formal sensor fusion frameworks. Such systems aim to overcome individual sensor limitations, enhance spatial and temporal resolution, and enable comprehensive monitoring of both gradual deformations and rapid, high-energy events such as rockfalls. This convergence of technologies represents a critical evolution in geotechnical monitoring, aligning with current industry imperatives for automated mining
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