地图综合中曲线局部尖锐凸角的光滑方法

Smooth method of local convex sharp angle in cartographic generalization

地图制图综合过程中,线状要素经过一系列的选取、化简等处理后,经常会生成少量尖锐的凸角。针对已有的算法在解决这个问题时大多对曲线上全部的节点进行整体光滑处理,在很多不必要光滑的地方增加了大量的冗余节点,且效率不高的问题,该文基于线性迭代法提出了一种曲线局部尖锐凸角的光滑方法。首先建立了基于角度阈值的尖锐凸角判断原则,然后据此设计了具有可控性的尖锐凸角自动识别处理方法,以探索最佳的角度阈值实现曲线光滑处理,最后以广州某市的地理国情普查水系数据为例对该文方法进行了检验。实验结果表明,当角度阈值在[150°,160°]范围内时,该文方法不仅消除了曲线局部尖锐的凸角,而且有较好的光滑效果和较高的处理效率。

In the process of cartographic generalization,after selection,simplification and a series of processing,the linear elements often generate some sharp convex angles.The existing algorithms to solve that problem are inefficient.Because most of these algorithms take all the nodes on the curve for the overall smooth processing and a lot of redundant nodes are added in places where there are no need to be smoothed.Thus,an algorithm based on the linear iteration was raised in this paper,which could smooth the local sharp convex of the curve.Firstly,the judgment rule of sharp convex based on angle threshold was established.And then a controllable automatic recognition processing method on sharp convex was designed,to find the best angle threshold to achieve the smooth curve processing.Finally,the experimental method of the algorithm proposed in this paper was carried out based on the hydrographic data of a city of Guangdong.The experimental results showed that the proposed method not only eliminated the local sharpness of the curve,but also had good smoothing effect and high processing efficiency when the angle threshold was in the range of [150°,160°].