## 4 Experiments and Results
### Results of 3D Visualization  
High resolution data have a stronger ability to display detail, and PS points can be accurately positioned on the building after ortho-rectification [39; 40]. Therefore, taking the buildings in the Fudian District of Shenzhen as the research goal, the elevation information of the PS points is imported into Google Earth for 3D visualization using the keyhole markup language (KML). Three-dimensional visualization can significantly improve the presentation ability of the results and can also verify the  
Figure 4: Permanent scatterer (PS) points distribution map. Red dot is the reference point for the unwrapping.  
Figure 5: The absolute elevation map (**a**) and deformation rate map (**b**) of the study area; the elevation is calculated by combining the SRTM (NASA’s Shuttle Radar Topography Mission) DEM and the height error.  
accuracy of the deformation by measuring the results from the side. See Figure 6, where the picture above shows all the \"standing\" PS points in the study area, and the following highlight the three landmarks: Figure 6b-d. The color represents their height values, and all of them are placed on the 3D building model from Google Earth. The PS height estimated by PSI has a high similarity with the 3D model, which can help facilitate the 3D reconstruction of urban buildings [41; 42].  
However, an interesting phenomenon was found. Figure 7 shows three-dimensional pictures of the FengHuang building. We found that the model built in Google Earth does not match the real scene map, and the PS point height we extracted is closer to that of the actual building. Therefore, the accuracy of the Google Earth 3D model can be verified by the 3D visualization of the PS height, which has not been mentioned in previous experiments.  
Figure 6: Three-dimensional visualization results of the PS height. (**a**) The panoramic view of PS height in the study area and (**b–d**) the local magnification of buildings (**b**), (**c**), and (**d**), respectively. The red rectangle represents the FengHuang building.  
By using PSI technology and a 3D visualization platform, an accurate deformation monitoring system can be established for high-rise buildings in urban areas. Figure 8 is a three-dimensional view of the PS point deformation rates, which can intuitively and completely read the deformation results of the high-rise buildings from top to bottom. On the three-dimensional map, the deformation of key parts of the high-rise building can be analyzed carefully, and we will get a comprehensive understanding of the health status of urban buildings. From the LOS deformation rate map, the overall performance is good. Except for the obvious adverse reactions of the four buildings, most of the buildings are stable. Next, we will analyze and discuss buildings with obvious deformation.  
Figure 8: Three-dimensional visualization results of the PS deformation rates. (**a**) The panoramic view of PS deformation rates in study area; (**b–e**) the local magnification of buildings b, c, d, e; the red points p1, p2, p3, and p4 are four deformation feature points on the buildings, and the boxes contain some buildings without PS points.  
Figure 7: (**a**) The Google Earth 3D model of the FengHuang building in Figure 6 and (**b**) its real scene map; (**c**) the three-dimensional representations of the extracted PS point heights geocoded in the Google Earth 3D model.