## 1 Introduction
Actually, MIDA-related GIS data or analysis results should be represented in a three-dimensional (3D) visual environment and hence, MIDA-related data visualization and analysis naturally requires a 3D or stereoscopic display environment. Owing to the rapid development of the Web Graphics Library (WebGL), the 3D visualization function of Web browsers has been greatly expanded. Due to no plug-in requirements, cross-browser compatibility (Chrome, Firefox, Internet Explorer, etc. ), graphical processing unit (GPU) program drawing, and other features, the WebGL is very suitable for network 3D display. 3D visualization technology based on the WebGL has been developed rapidly [PERSON] et al. (2018). The \"virtual earth\" technology based on the WebGL has opened up a new way for the display and processing of GIS data. For example, 3D virtual visualization technologies (such as Google Earth, NASA World Wind, and Cesium), which integrate geo-spatial data from all over the world, enable researchers to interact in real 3D virtual scenes and it has proven to be a very ideal visual environment Bing and Google Maps (2018). Many studies have pointed out the role of 3D visualization technology in the fields of environmental protection Bing and Google Maps (2018); [PERSON] et al. (2018), hydrology [PERSON] et al. (2018), and oceanographic science [PERSON] et al. (2018). These studies portray a different hazardous event's occurrence, development, and evolution by a professional numerical simulation model at different scale levels. Although the flowcharts of these studies are similar to the MIDA applications, they do not fully cover GIS data collecting, storage, and spatial analysis, and thus, GIS functionality is not deeply involved in these studies. It should be noted that, recently, the 3D webGIS-based approach to preventive conservation of heritage buildings has become a hot topic [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018). These studies took full use of GIS and WebGL visualization techniques by integrating multiple sources, i.e., building information modeling (BIM), 3D point clouds, real-scene 3D models, 360 panoramas, or the data of the Internet of things (IoT), to carry out building information management and health monitoring. Good resources of 3D GIS data are necessary to construct a 3D webGIS application. 3D modeling based on real scenes is an important data source in GIS research, which mostly comes from oblique images and laser scanning. The joint application of the structure from motion (SfM) technique and unmanned aerial vehicles (UAVs) makes it possible to reduce cost and time. As a new remote sensing method, it has become one of the hotspots in geoscience research [17]. It includes some computer vision algorithms, such as feature extraction and bundle adjustment (BA) [19; 20]. So far, SfM-based 3D reconstruction has been widely used in many fields, such as geological disaster monitoring [21; 22], open-pit mining planning [23], cultural heritage protection [24; 25], and the structural health monitoring of infrastructures (such as dams) [26]. On the other hand, light detection and ranging (LiDAR) scanning is among the most accurate remote sensing methods available to acquire spatial data, ensuring measurement accuracy at a few millimeters or centimeters [27]. Laser scanning techniques can be divided into two types: space-based and ground-based. Ground-based LiDAR is a commonly used method to measure the three-dimensional spatial structure or geometric shape of objects, which includes the monitoring of building component deformation and surface deformation [28]. However, ground-based or airborne-based LiDAR techniques are not always feasible for the large-scale scenes investigated in this work due to high investment or leasing costs and inevitable occlusions that restrict their broader applications. In some cases, ground-based LiDAR is often adopted only as a complementary method of oblique photogrammetry to acquire more detailed information about the occluded object [28].