# Selection of Grid Road Networks Based on Raster Data
## 4 Experiments and Evaluations
### Experimental Results and Analysis
Based on the length and area of the original and selected road networks, the GS indicators of the two methods are calculated in Table 1. The GS values of the vector-based ArcGIS method at the two selection levels are 0.74 and 0.52, which are both lower than those of the proposed raster-based AWRS method (0.92 and 0.69, respectively). Thus, the proposed raster-based AWRS method has a better ability to preserve the geometrical similarity than the vector-based ArcGIS method. This is mainly because the raster-based AWRS method can automatically identify the road width by multilevel division based on superpixel segmentation, while the vector-based ArcGIS method can only process the road networks that ignore the width information. The \(TC\) indicator is usually applied to measure the reachability degree among the intersections of road network structures during the selection operation [43]. The \(TC\) indicator can be calculated using the following equation:  
\[TC=\frac{\Sigma_{m\in G}\Sigma_{n\in Dm\
eq n}P_{mn}}{G(G-1)} \tag{7}\]  
In this equation, \(G\) means the total number of pairs of nodes. When there is a connected path between nodes \(m\) and \(n\), the value of \(P_{mn}\) equals 1; when there is no connected path between nodes \(m\) and \(n\), the value of \(P_{mn}\) equals 0. If \(TC=0\), the topological integrity of the road network architecture is disconnected; if \(TC=1\), the road network architecture manifests total topological interconnectivity. As shown in Table 1, the original number of route sections handled by the ArcGIS method is 1832. After selection using the ArcGIS method, the numbers of selected road segments at the two target levels are 1040 and 638, which are reduced by 43.2% and 65.2%, respectively. The original numbers of road superpixels at the two levels handled by the proposed AWRS method are 46,852 and 14,363. After selection using the proposed AWRS method, the numbers of selected road superpixels at the two target levels are 36,063 and 9697, which are reduced by 23.0% and 32.5%, respectively. Referring to the connectivity of the original and selected route sections, the \(TC\) indicators of the two methods are calculated and shown in Table 1. The \(TC\) numbers of the vector-based ArcGIS method between both chosen levels are 0.99 and 1.00, which are both close to those of the proposed raster-based AWRS method (1.00 and 1.00, respectively). Thus, both the vector-based ArcGIS method and the proposed raster-based AWRS method perform well in topological connectivity. The value of the \(PD\) indicator can be acquired by calculating the quantity change in forks of the main roads at different levels of detail, as follows:  
Figure 7:0  
The quantities \(N_{a}\) and \(N_{b}\) denote the number of junctions on major thoroughfares with varying levels of intricacy post- and preselection, respectively. According to Table 1, the \(PD\) metrics for the vector ArcGIS technique at its two selection phases (0.69 and 0.51) fall short of the raster-based AWRS method's scores (0.78 and 0.56). This suggests that the AWRS method excels at retaining pivotal road network hubs during the selection steps. We also compared the distribution density of the road selection results using the ArcGIS and AWRS selection sections, which can be seen in Figure 7:1 Figure 12a shows the distribution density of the original road networks. Figure 12b,c show the distribution density of the selected road networks at two levels of detail using the ArcGIS method, and we can see that, in some regions, the original distribution density is relatively high, while the selected distribution density is relatively low, such as in region \(M\). However, as shown in Figure 12d,e, although both methods can cause changes in density, the proposed AWRS method is more effective at retaining the comparative distribution density of road systems. For instance, the high-density road networks located in region \(M\) are still high-density, while the low-density road networks located in region \(N\) are still low-density.