An elimination method for isolated meshes in a road network considering stroke edge feature

Abstract

The road network is the skeletal element of topographic maps at different scales. In general, urban roads are connected by road segments, thus forming a series of road meshes. Mesh elimination is a key step in evaluating the importance of roads during the road network data management and a prerequisite to the implementation of continuous multiscale spatial representation of road networks. The existing mesh-based method is an advanced road elimination method whereby meshes with the largest density are sequentially selected and road segments with the least importance in each mesh are eliminated. However, the road connectivity and integrity may be destroyed in specific areas by this method because some eliminated road segments could be located in the middle of road strokes. Therefore, this paper proposed an elimination method for isolated meshes in a road network considering stroke edge feature. First, small meshes were identified by using mesh density thresholds, which can be obtained by the sample data statistical algorithm. Thereafter, the small meshes related to the edge segments of road strokes were taken out and defined as stroke edge meshes, and the remaining small meshes were defined as stroke non-edge meshes. Second, by computing the mesh density of all stroke edge meshes, the mesh with the largest density was selected as the starting mesh, and the least important edge segment in the mesh was eliminated. The difference between the existing mesh-based method and the proposed method is that the starting mesh is a stroke edge mesh, not any given small mesh, and the eliminated segment is just only one of edge segments of strokes not chosen from among all segments. Third, mesh elimination was implemented by iteratively processing the stroke edge meshes with the largest mesh density until all of them were eliminated and their mesh density exceeded the threshold. The stroke non-edge meshes were directly preserved. Finally, a 1:10,000 topographic road map of an area in Jiangsu Province of China was used for validation. The experimental results show that for all stroke non-edge meshes and 23% of the stroke edge meshes, compared to the mesh-based method, the road stroke connectivity and integrity of road strokes were better preserved by the proposed method, and the remaining 77% of the elimination results for the stroke edge meshes were the same under the two methods.

An Automatic Generalization Method for a Dense Road Network Area Considering Spatial Structural Features as Constraints

“…The traditional mesh-based approach was proposed by Chen et al [8], in which mesh is defined as a closed region surrounded by several road segments. The detailed steps in this method are given as follows [8,10]:…”

“…Step 6: Compare the importance of bounding road segments and eliminate the leastimportant segment. The importance of each edge segment is calculated with Equation (2) [8,10]:…”

“…Chen et al [8] proposed a sample statistical algorithm in which the appropriate threshold value is determined based on the split nodes of the mesh density distribution curves at two scales before and after the road network generalization. For example, practical experiments proved that 0.016 m/m 2 is considered an appropriate value of the density threshold for transformation from a 1:10,000 to 1:50,000 urban road network data [10]. Correspondingly, meshes with mesh densities larger than the threshold are defined as small meshes.…”

“…With these selection constraints, maintaining the spatial distribution structure of the road network is the most difficult part; hence, the structured selection of road networks has been recently studied in detail. Among these studies, the mesh-based approach [8] has been reported to be a common, advanced, and powerful model to complete road selection work in dense road areas [5,9,10]. The research in this paper also falls into this field.…”