Selective omission of road features based on mesh density for digital map generalization

Selection of roads is an intractability generalization operation, due to the difficulty in retaining the density difference and connectivity of a road network. This paper proposes a new approach of selective omission for roads based on meshes density. Density of roads is calculated using meshes as units and represents local region density in a network. Usually, the density is different between maps with different scales. The density thresholds are acquired by theoretical analysis and empirical study for mesh density on different scale maps. For meshes with density over threshold, the largest density meshes are taken out by turns and one road segment of them is eliminated. Meanwhile the taken mesh is merged with the adjacent mesh at a time. Road segment to be eliminated is the most unimportant in all segments on the boundary of this mesh according to the parameters reflecting the importance of road segments. In this study, the meshes are classed depending on the types of road segment. For the different type meshes, their thresholds are different, which can preserve the density difference. The process of eliminating road segments and merging meshes would ensure the road network connectivity. This proposed approach considers topological, geometric and semantic properties of the road network. A road network is selective eliminated employing this approach, and the results of selection achieve better effects.