## 6 Results and Discussion
### Results  
Based on topographical surveys, a set of terrain elevation points and a 3D detailed survey of routes and buildings have been acquired. Then, this data is exported to ArcGIS in order to implement our HybVOR approach for the placement of the camera network and performing the analysis of the expected level of coverage.  
For this purpose, the first step is to generate a Raster Digital Elevation Model (DEM) from the set of terrain elevation points structured in a Triangular Irregular Network (TIN). Then, the buildings' footprints are produced from the 3D detail survey and assigned a value of elevation to each footprint  
Figure 17: General overview of Jeddah Seaport and the study area (image from Google Maps).  
based on the elevation of the corresponding building. Thereafter, these footprints are transformed to raster format, and they are combined with the DEM in order to generate a Raster Digital Surface Model (DSM) of the region of interest. This DSM is the basis of our raster based viewshed calculation (_c.f._ Section 5.3). Figure 18 shows the DEM and the DSM that were used in our raster based viewshed calculation.  
The second step consists of generating the Voronoi diagram (in vector format) based on buildings' footprint. Then, a camera network is placed according to HybVOR approach on the divided Voronoi edges as explained in Section 5.2. Figure 19 illustrates the placement of the camera network in our study area based on HybVOR approach. It is important to notice that, in theory, the Voronoi edges generated from polygons should appear as parabola curves. However, due to the drawing limitation of the used GIS software, the parabola curves are approximated to line segments, and this approximation will not affect the quality of coverage assessment [35].  
In the third phase, the viewshed is calculated based on the generated raster DSM and cameras' position. The main purpose of this phase is to ensure that the road network is fully covered by the surveillance camera network. Regarding the elevation of cameras, it corresponds the tallest building to be monitored from this location (_c.f._ Section 5.3). Figure 20 shows the level of surface coverage obtained by applying the HybVOR approach in the region of interest.  
Figure 18: The Digital Elevation Model (DEM) and Digital Surface Model (DSM) used for raster based viewshed calculation.  
Figure 19: Camera network deployment on the study area based on HybVOR approach.  
Figure 20: Surface coverage generated from the DSM and the proposed cameras’ location.  
The last phase in implementing the HybVOR approach is performing the 3D Vector-based analysis of visibility. The objective of this step is to ensure that the main entrances of buildings (doors, windows, _etc._) are fully monitored from the proposed location of cameras. In the case where some entrances are not entirely visible, the position of the corresponding cameras is manually changed in order to improve the visibility (minor displacements that do not affect the surface coverage are carried out). Figure 21 illustrates the results of our 3D Vector-based analysis of visibility based on HybVOR approach.