# Selection of Grid Road Networks Based on Raster Data
## 4 Experiments and Evaluations
### Experimental Results and Analysis  
Figure 7a-c display the various-scale visual representations of Beijing's road systems, achieved through the application of the proposed AWRS technique across three distinct levels of detail, a popular road network selection method that can be realized in the \"Cartography\" toolbox of ArcGIS software to achieve contrast experiment outcomes. The ArcGIS road selection method can remove redundant road line segments by considering the overall character, connectivity, and density, and it is widely used in the field of the multiscale representation of vector map elements [42]. The multiscale visualization results of the road networks generated from the ArcGIS method are shown in Figure 7d,e. The generated simplified road set is determined by the meaning, significance, and density of the features. Across the entire dataset, segments belonging to longer routes are more important than those used only by local pedestrians. The classification (importance) of roads can be specified through the hierarchy field parameter. The density of the generated street network is controlled by the minimum length parameter, which corresponds to the shortest segment that needs to be clearly displayed at the current scale. The minimum length parameters in the ArcGIS method at the two selected levels are 300 and 700 m. In contrast to the conventional ArcGIS approach tailored for vector-based road systems, as illustrated in Figure 7, our proposed technique offers four distinct benefits:  
1. **Semantic feature preservation**. Roads with different widths have different semantic functions. Without manual grading, the traditional ArcGIS method based on vector roads cannot automatically preserve relatively wide road segments with prior semantic attributes. For example, in Figure 8a, the road segments in the regions marked with red rectangles are improperly removed even though they are the main roads with large widths relative to those of the surrounding roads. However, since the proposed raster-based AWRS selection method has the ability of the multilevel division of raster road networks, it can automatically identify the width of the road, and road segments with prior semantic features can always be preserved, for instance, the road segments selected within the areas delineated by green rectangles. In comparison, the proposed raster-based AWRS selection technique surpasses the traditional vector-based ArcGIS technology in preserving the semantic features of road networks;
2. **Global structure preservation**. The pattern of road networks typically reflects the global structural characteristics of road networks. A good road selection method should effectively preserve the original road pattern after removing the redundant road segments. By using the traditional ArcGIS method, Figure 9a shows an example of road network selection, and we can see that the original grid pattern of the road networks is destroyed and thus the global structure of the road networks cannot be well preserved. Figure 9b illustrates the outcomes of the selection process within the same area utilizing the proposed AWRS technique. The proposed AWRS approach,  
Figure 6: Processing in batches of non-connected road areas. (**a**) Original segmented road superpixels. (**b**) Superpixels divided into 3 parts. (**c**) Road intersection superpixel matching results. in contrast to the ArcGIS method, successfully preserves the grid layout of the initial road system;  
Figure 7: Multiscale visualization results of road network selection using the ArcGIS and AWRS methods. (**a**) Original visual representation of Beijing’s road system. (**b**) Level 1 result using AWRS method. (**c**) Level 2 result using AWRS method. (**d**) Level 1 result using ArcGIS method. (**e**) Level 2 result using ArcGIS method. 3. **Local connectivity preservation**. Compared with general branches, the road branches that are directly connected to the main road play a more important role as hubs, which have higher priority for preservation.