基于QTM的线状图形自动化简算法探讨

全球网格是由形成地球表面剖分的一系列区域所组成,八面体四分三角网(QTM)是其中一种具有层次性的网格。本文依据数据点在规则网格中的分布规律,提出了一种在QTM数据结构支持下的线状图形化简算法。该算法以经过每级QTM网格的数据点的平均值为标准,能自动地对比较平缓的线段进行较粗选点,而对相对复杂的线段进行较密选点。本文以及Dutton算法都能克服DouglasPeucker算法中难以客观和合理确定阈值的困难,但是本算法比Dutton算法简单,且具有更高的化简率,能更好地保留了线状图形的弯曲特征。

Algorithm for automated line simplification based on QTM

A global grid consists of a set of regions that form a partition of the earth's surface,octahedral quaternary triangular mesh(QTM),is one of hierarchical triangular tessellations.This paper presents an algorithm of QTM-based line simplification,which is built on the distribution characteristics of polyline vertices in a regular grid.The algorithm takes the average point number at every QTM level as criterion,automatically selects points in the bigger QTM facets for the smoother line segments and in the smaller grids for the relatively sinuous sections.Both Dutton's and our algorithms would overcome the difficultly of Douglas-Peucker method in determining thresholds.Compared with Dutton's algorithm,ours is easier to be implemented,and yield a larger reduction ratio and better perserve cartographic line characteristics.