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为解决现有地理信息系统无法完成城市轨道交通三维缓冲区构建的难题,采用八叉树作为构建三维缓冲区的基础数据结构,用线性八叉树编码储存轨道交通实体的空间结构信息,将交通三维缓冲区分析转化为八叉树节点的空间分析。研究了八叉树节点的空间关系,得出了一种线性八叉树邻域分析的新算法,即0-1互换算法。运用0-1互换算法找出轨道交通的边界节点,确定边界节点的边界方向,由边界节点构建交通三维缓冲区,形成了一套由线性八叉树构建城市轨道交通三维缓冲区的新方法。运用0-1互换算法对直线隧道、曲线隧道、直线高架桥、曲线高架桥等轨道交通实体模型进行边界节点提取,并与传统算法和经典肖氏算法进行了比较。选择连拱隧道、单拱隧道和高架桥3种结构,分别进行了三维缓冲区构建,统计了3种结构分割的八叉树节点数量,并与采用传统栅格结构进行三维缓冲区分析的栅格节点数量进行对比。分析结果表明:与传统算法和经典肖氏算法相比,0-1互换算法在对直线隧道、曲线隧道、直线高架桥、曲线高架桥4种轨道交通实体模型的边界节点提取中耗时最少,分别为5、7、10、18ms,将算法的时间复杂度由二次阶减少为一次阶;基于线性八叉树的交通三维缓冲区构建方法,对连拱隧道、单拱隧道与高架桥进行三维缓冲区构建时,其存储空间分别为栅格结构的7.26%、3.64%、3.72%。可见,基于线性八叉树结构的交通三维缓冲区构建方法能显著降低分析节点数量,提高交通三维缓冲区的构建效率。
In order to solve the problem that existing GIS can not complete the construction of three-dimensional buffer in urban rail transit, octree is used as the basic data structure to construct 3D buffer. Linear octree coding is used to store the spatial structure information of rail transit entities, Spatial analysis of octree nodes transformed by 3D buffer analysis. The spatial relations of octree nodes are studied, and a new algorithm for neighborhood analysis of linear octree is obtained, ie the 0-1 exchange algorithm. The 0-1 exchange algorithm is used to find the boundary nodes of the rail transit, the boundary direction of the boundary nodes is determined, and the traffic three-dimensional buffer is constructed by the boundary nodes. Thus a new method of constructing the three-dimensional buffer of urban rail transit by linear octree is formed . The 0-1 exchange algorithm is used to extract the boundary nodes from the solid model of the rail transit such as straight tunnel, curved tunnel, straight viaduct and curve viaduct, and compared with the traditional algorithm and the classical algorithm. Three kinds of structures, including multi-arch tunnel, single-arch tunnel and viaduct, were selected and three-dimensional buffer structures were constructed respectively. The number of octree nodes in three kinds of structural segmentation was counted and compared with those of grids using traditional grid structure for three-dimensional buffer analysis Compare the number of nodes. The analysis results show that compared with the traditional algorithm and the classical algorithm, the 0-1 exchange algorithm takes the least time to extract the boundary nodes of the four kinds of rail transit solid models of straight tunnel, curved tunnel, straight viaduct and curved viaduct, respectively 5,7,10,18ms, the time complexity of the algorithm is reduced from the second order to the first order. Based on the linear octree traffic 3D buffer construction method, the three-dimensional buffer of double-arch tunnel, single-arch tunnel and viaduct Area construction, the storage space for the grid structure of 7.26%, 3.64%, 3.72%. It can be seen that the construction method of traffic three-dimensional buffer based on linear octree structure can significantly reduce the number of nodes and improve the construction efficiency of traffic three-dimensional buffer.