线要素移位的Morphing变换方法

An Extended Morphing Approach for Linear Feature Displacement

移位是解决地图制图和GIS中空间冲突的基本算子之一。Morphing变换可以实现源对象到目标对象的连续平滑变换,通过从两个方面拓展Morphing变换,从而实现对线要素进行移位。首先分析了线要素空间冲突的类型。在线要素弯曲识别的基础上,以弯曲作为冲突检查和线要素移位的基本单元;然后,用Delaunay三角网探测冲突区域,将冲突位置定义在局部的线要素弯曲(组);最后拓展Morphing变换实施线要素移位,即先对冲突发生弯曲(组)进行镜像变换,再对冲突发生弯曲(组)和它们的镜像进行Morphing变换,并给出了变换参数与移位距离和方向的定量关系。实验证明了该方法有效、可行。引入图形镜像避免了普通Morphing变换中的特征点识别和匹配等两个难点。将弯曲作为冲突发生的范围和化解冲突的操作单元,可以实现要素局部与全局移位的有机统一。

Displacement is one of the basic operations for solving spatial conflicts in cartographic mapping and GIS.Morphing can achieve continuous transformation from the source object to the target.In this paper,an extended Morphing approach was proposed for linear feature displacement.Firstly,the categories of spatial conflicts were analyzed.Bends of linear features were recognized and treated as the units of spatial conflicts detection and displacement.Then spatial conflicts were detected by using Delaunay Triangulation and the conflict regions were defined in the regions of local bends.Finally,conflicts between linear features were displaced by using extended Morphing.In this strategy the mirror transformation was firstly used to detect the conflict bends,then the conflict bends and their mirrors were used to perform extended Morphing.Quantitative relationship of transformation parameter and displacement distance and orientation were given.Experiments on real dataset showed that this proposed strategy was effective and practicable.The difficulties in feature points detection and matching were avoided by introducing bends mirror to extended Morphing.Local and global displacement were unified by taking bends as the units of spatial conflicts detection and displacement operation.