3D buffer zone creation method of urban rail transit
- Publication Type:
- Journal Article
- Jiaotong Yunshu Gongcheng Xuebao/Journal of Traffic and Transportation Engineering, 2015, 15 (2), pp. 100 - 108
- Issue Date:
©, 2015, Chang'an University. All right reserved. In order to solve the problem that the existing GIS buffer algorithm can not create the 3D buffer zone of urban rail transit, octree was adopted as a fundamental data structure for creating the 3D buffer zone. The 3D solid information of urban rail transit was stored by using linear octree encoding, and the analysis of 3D buffer zone was transferred into the spatial analysis of octree nodes. The topology of octree nodes was analyzed, and a new algorithm, i.e. 0-1 swap algorithm, was proposed for linear octree neighborhood analysis. The boundary nodes of rail transit were identified by using the 0-1 swap algorithm, and the directions of boundary nodes were determined. The 3D buffer zone of rail transit was created by using boundary nodes. A new 3D buffer zone creation method of urban rail transit was formed based on linear octree. The boundary nodes of straight tunnel, curved tunnel, straight viaduct and curved viaduct were created by using the 0-1 swap algorithm, and the result was compared with that of conventional algorithm and classical Xiao's algorithm. The 3D buffer zones of double-arch tunnel, single-arch tunnel and viaduct were created by using the proposed method, and the number of octree nodes extracted from the different structures was counted and compared with the number of raster nodes of traditional structure. Analysis result indicates that compared with the conventional algorithm and the classical Xiao's algorithm, the elapsed times of boundary nodes creation for straight tunnel, curved tunnel, straight viaduct and curved viaduct are minimum by using the 0-1 swap algorithm, and the values are 5, 7, 10, 18 ms respectively. The time complexity reduces from second order to first order by using the 0-1 swap algorithm. For the 3D buffer creation method based on linear octree, the memory spaces of octree data structures are 7.26%, 3.64% and 3.72% of the spaces of raster structures when the 3D buffer zones of twin-arch tunnel, singel-arch tunnel and viaduct are created. Therefore, the 3D buffer zone creation method greatly reduces the number of analysis nodes, and improves the efficiency of creating the 3D buffer zone. 2 tabs, 11 figs, 25 refs.
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