河流自动选取中的分级优化

水系是具有高度结构化特征的复杂空间数据,在不同水文条件和地形环境下发育的水系形态可以表现为多种模式,如格状河系、羽毛状河系、平行状河系等,使得水系选取具有较大难度。探讨了河流分级(汇流区域特征)、河网结构层次化(河流分布的地理特征)与水系选取之间的关系,提出了基于流域的河流自动选取,从河流的局部重要性出发,考虑河流的分级主要基于两点:一是确定选取单元为流域;二是对流域内河流通过等级关系选取高等级河流,同等级间河流根据长度、密度、河流间距离等综合指标进行选取。

River Classification and River Network Structuration in River Auto-selection

River auto-selection is an essential part of automatic thematic map generalization.When ac-complishing the selection,it is critical to reasonably evaluate each river’s importance in the globalstructure.A grading system is needed to quantify the importance of each river.In this system,theimportance of a river differs at different levels.Although several grading systems(Horton,Strahler,etc.)are already in use,each with its strengths,still they cannot completely meet the requirementsfor river auto-selection,therefore,a basin-based grading system of river classification is proposed inthis study.Each river’s importance in partial river networks is considered and selected accordingly.This system can make the density of the selected rivers as consistent as the entire network.