## 2 Study Area and Data
### Mine Big Data
#### 2.2.1 UAS Imagery--Multispectral, LiDAR, Aeromagnetic  
With the rapid development of drone technology, its application in mineral exploration has become increasingly mature and widespread, providing new directions for research and application in the fields of geological and geophysical exploration. This study used a Matrice 350 RTK drone produced by DJI (Shenzhen, Guangdong, China), equipped with multiple sensors, to acquire multi-temporal remote sensing imagery of the Yanshan iron deposit. First, multi-temporal UAV Structure-from-Motion (UAV-SFM) aerial imagery of the mining area was captured using the Zenmuse L1 sensor produced by DJI (Shenzhen, Guangdong, China). This sensor integrates Livox LiDAR, high-precision inertial navigation (RTK), and RGB cameras, enabling all-weather, efficient, and real-time 3D data acquisition in complex environments. This allowed for the generation of high-precision 3D surface models (Figure 2a) and 2D visible light orthophotos (DOM) (Figure 3a-c). The Digital Surface Model (DSM) aids in the 3D visualization and reconstruction of the mining area [49]. The results of the Digital Surface Model (DSM) clearly reveal the surface features of the open-pit mine, including the distinct boundary between the sandstone and gravel layers and the underlying strata on the southwestern side (Figure 2b). On the northeastern side, the formation of the pit slope shows significant folding patterns in the strata (Figure 2c). In the currently mined area, the boundary between the surrounding rock (black cloud metamorphic granite) and the ore body (magnetic quartzite) is unclear under visible light. After blasting, the mixed areas of ore and rock are prone to increasing ore loss and waste rock contamination, which affects the recovery rate of iron ore (Figure 2b,d). Meanwhile, the digital orthophoto maps (Figure 3a-c) provide reference images for selecting surface sampling points [50]. Figure 2: Digital Surface Model of Yanshan Iron Mine Open-Pit: (**a**) Global model of the open-pit; (**b**) Mixed ore and surrounding rock in the western part of the open-pit; (**c**) Northeastern slope of the open-pit; (**d**) Key mining area at the central-bottom section of the open-pit. Additionally, multi-temporal multispectral imaging was conducted using the MS600 Pro multispectral sensor produced by Yusense (Qingdao, Shandong, China), with a spatial resolution of 8.5 cm. The spectral bands of the sensor are as follows: Blue (450 \(\pm\) 35 nm), Green (530 \(\pm\) 27 nm), Red (650 \(\pm\) 25 nm), Red Edge (720 \(\pm\) 10 nm), Near Infrared (840 \(\pm\) 26 nm), and 900 \(\pm\) 35 nm. During the flight, the aircraft captured images at an altitude of 80 m AGL along the flight path, ensuring a 75% forward overlap and 65% side overlap, while the RTK system provided precise positioning. Finally, Yusense Map was used for image registration, stitching, and radiometric calibration, generating high-precision multi-temporal UAV multispectral imagery (Figure 4). Figure 4a-c show the false-color composite results of multispectral imagery for the mining area for three different periods (Red: 650 \(\pm\) 25 nm, Green: 530 \(\pm\) 27 nm, Blue: 450 \(\pm\) 35 nm). When combined with the digital orthophoto maps (true-color images from different periods shown in Figure 3a-c), they further confirm the complexity of visually interpreting the ore body (magnetite quartzite) and surrounding rock (black cloud metamorphic granite) within the visible light range. This highlights the need for a series of subsequent processing steps to effectively delineate the surface ore and rock. Figure 3: Spatial distribution maps of the three stages of sampling and iron grade distribution of samples: (**a**) samples collected in April 2023; (**b**) samples collected in September 2023; (**c**) samples collected in May 2024; (**d**) kernel density of iron grades for all samples; (**e**) box plot of iron grades for samples from each stage.