A method for elliptic arc proccessing in coordinate transformation of DLG data
For coordinate transformation of digital line graphic(DLG)data,the center of the elliptical arc is required to join the coordinate transformation calculation when the methods previously proposed by others are used to process elliptical arcs.Moreover,they cannot be used if the center of the elliptic arc is beyond the controlling range of the transformation model when it is considered.Even if the center of the elliptic arc is within the range,topological errors can often be generated at the intersection of the elliptical arc and other shapes if a coordinate transformation model with inconsistent changes in each point,such as the grid model,is used to process large-scale elliptical arcs.In order to solve the above problem,the key point set alternative graph method is proposed in this paper.The fundamental princi-ples of the method is to use the key point set consisting of selected points on the elliptic arc to join coor-dinate transformation instead of elliptic arc itself,then calculate new parameters by transformed point set and the mathematical model of the elliptic arc,and draw new elliptic arc by related interfaces,and complete the coordinate transformation.The results show that whether the center of the elliptical arc is within the controlling range of the transformation model or not,the data of the elliptical arc processed by the method are correct and reliable.Compared with the previous methods,the method proposed in this paper is more ubiquitous and has good practical values,it can be widely used in the future.
DLG datacoordinate transformationelliptic arctransformation model
万方数据
维普
