## 3 Study Area and Data Source Analysis
### Data Source and Feature Analysis  
An analysis was conducted of the spatial interpolation data sources--terrain elevation, stratum, and coal seam thickness--within 300 m near the 25214 workforce. (1) Terrain data  
Figure 3: Stratigraphic composite histogram. Figure 2: Location of study area. The data sources for terrain interpolation consist of elevation measurement points obtained from aerial photogrammetry using an unmanned aerial vehicle (UAV) equipped with a high-resolution camera, and from Real-Time Kinematic (RTK) positioning surveys. Both datasets cover the entire mining area; however, this study extracted a total of 1700 elevation points within the 25214 workforce and its 300 m extended boundary (Figure 4). Within this range, the UAV photogrammetric data points are densely distributed. These points were obtained through the deployment of ground control points and aerial triangulation densification processing, ensuring high positional accuracy. In contrast, the RTK survey data points are more sparsely distributed, as they were collected using conventional ground surveying methods. Although the two datasets differ in acquisition techniques and individual point accuracies, both are considered high-precision measurements. Therefore, they are treated as \"hard data\" in the interpolation process, providing a reliable basis for terrain modeling. Formation thickness data for the study area were obtained from 27 boreholes, the spatial distribution of which is shown in Figure 5. These boreholes provide thickness measurements for five primary stratigraphic units: the Quaternary (Q4), Neogene Baode Formation (N2\(b\)), and Jurassic Yan'an Formation members (J2\(y^{3}\), J2\(y^{2}\), J2\(y^{1}\)). Due to variations in borehole depths, data for the J2\(y^{2}\) and J2\(y^{1}\) units were available from 20 boreholes, whereas the remaining 7 boreholes did not reach these deeper strata. Figure 4: Elevation point distribution map. Figure 5: Normal distribution curve of elevation points. The thickness ranges of the five stratigraphic units are summarized in Table 1 as follows: Q\({}_{4}\) (0-90.29 m), N\({}_{2}b\) (0-92 m), J\({}_{2}y^{3}\) (11.3-48.15 m), J\({}_{2}y^{2}\) (51.06-81.4 m), and J\({}_{2}y^{1}\) (6.85-30.15 m). The Q\({}_{4}\) and N\({}_{2}b\) formations exhibit substantial thickness variability across the workforce, reflecting notable stratigraphic undulation and local erosion. In contrast, the J\({}_{2}y^{3}\), J\({}_{2}y^{2}\), and J\({}_{2}y^{1}\) units generally show more uniform thicknesses, though localized variations are still present. Furthermore, local absences of certain strata, particularly Q\({}_{4}\) and N\({}_{2}b\), were observed in some boreholes, indicating erosional truncation or non-deposition in specific areas. These spatial discontinuities further highlight the heterogeneity in the overlying strata. Collectively, these stratigraphic data provide the fundamental basis for subsequent geological modeling and interpolation analyses. (3) Coal seam data  
The interpolation data for coal seam thickness in the 25214 workforce were obtained from multiple sources, including borehole measurements, roadway exposure measurements during tunnel excavation (Figure 6), and channel wave exploration inversion results. During tunnel excavation, coal seam thickness was measured along the roadway with an average spacing of approximately 50 m between measurement points. These measurements were used to assist in roadway positioning and adjust the excavation direction. Notably, seam thinning was observed approximately 500 m from the retreat support roadway, where a sandstone scour zone had eroded the seam. To further delineate this thinning anomaly, channel wave exploration was conducted within the range of 310-690 m from the retreat roadway, and the seam thickness was inferred by inverting the channel wave group velocity. The layout for the channel wave exploration at 25214 workforce is depicted in Figure 7. Twenty shot points and forty-two receiver points were planned for each of the two survey lines.