## 4 Discussion  
Owing to the important social effect of mining activities, there is an urgent need to obtain early alarming risk information. The main contributions of this paper are to propose a unified multi-scalar oblique photogrammetry-supported web-based framework including 3D realistic and virtual modeling, GIS vector data acquisition and storing, and the corresponding web-based prototype system development. The proposed framework allows non-professionals to perform complicated MIDA tasks and use a 3D webGIS in the mining industry to a large extent. The proposed framework is still worth discussing as follows. Compared to traditional fieldwork, UAVs are suitable for surveying large areas of the Earth's surface because they generate low-cost oblique photogrammetry, contribute to constructing realistic 3D models, and allow for recording and measuring the areas of interest. The resulting data products can be used as an important data source for GIS applications. Despite this, in practice, there is always a conflict between model quality and flight efficiency. Aiming at this problem, a technical pathway of multi-scalar photogrammetry was proposed by fully considering the shooting performance of different UAVs to balance the data acquisition efficiency and model quality, which is particularly essential for the large-scale regions examined in this work. The visual inspection and \begin{table}
\begin{tabular}{c c c c} \hline
**No.** & \(\Delta X\) **(cm)** & \(\Delta Y\) **(cm)** & \(\Delta H\) **(cm)** \\ \hline
1 & 1.9 & 7.5 & 8.3 \\
2 & 3.1 & 0.8 & 6.9 \\
3 & 6.6 & 0.9 & 10.2 \\
4 & 1.6 & 0.5 & 4.8 \\
5 & 0.7 & 5.8 & 7.9 \\
6 & 1.2 & 1.6 & 2.6 \\
7 & 2.2 & 0.8 & 8.5 \\
8 & 1.8 & 1.2 & 7.9 \\
9 & 3.2 & 1.3 & 10.5 \\
10 & 0.9 & 1.2 & 8.3 \\
11 & 2.2 & 1.5 & 6.9 \\
12 & 2.7 & 1.4 & 7.2 \\
13 & 1.6 & 0.8 & 5.1 \\ \(\ldots\) & \(\ldots\) & \(\ldots\) & \(\ldots\) \\
31 & 2.6 & 1.4 & 2.5 \\ \hline \multicolumn{3}{c}{_RMSEs_} & 2.3 & 7.6 \\ \hline \end{tabular}
\end{table} 
Table 6: Assessment results of absolute accuracies of the web-based application system. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**No. ** & \(D_{\text{Arc}}\) **(m)** & \(D_{\text{web}}\) **(m)** & \(\Delta D\) **(cm)** & \(\mathbf{S_{\text{Arc  
precision assessment results verify that multi-scalar photogrammetric 3D modeling ensures the model's effectiveness and achieves centimeter-level accuracy, which meets practical engineering needs. Taking the oblique photogrammetric data as an important data source, a technical workflow for GIS dataset production and a storage method were proposed. Regarding modeling 3D data, aside from the 3D realistic model, the 3D virtual model of power corridors distributed in the mining area was constructed using third-party 3D modeling software based on the actual size derived by the photogrammetric LT method. The above two 3D model datasets in our 3D webGIS system are the background data layers to enhance the 3D virtual environment. Concerning GIS vector data, many involved GIS data are collected from the 3D realistic model in the Cesium environment and managed by the GIS database. In our case study, the main consideration of selecting photogrammetric data as the main data source is to reduce the computational burden and complexity of multi-source data processing usually adopted by existing studies. Moreover, a web-based graphics platform was developed to visualize geographic data and web-based MIDA tasks. The proposed framework reduces the mining industry personnel's knowledge requirements for mining deformation. The users do not need to pay special attention to the details of MIDA. Additionally, each key process in the framework has its data interface operation commands, which reduces the difficulty for mining designers to master and understand expert knowledge quickly. On the other hand, during the implementation of this prototype, open-source technologies and tools were used to provide a more open, transparent, and flexible solution.