空间视域分析方法在八达岭长城风景林分类配置中的应用

Application of spatial viewshed analysis in classifying scenic forests along the Badaling Great Wall

以八达岭长城沿线风景林为研究对象,利用空间视域分析技术,在ERDAS virtualGIS平台上,将八达岭长城风景林和游客同时置身于一个虚拟的三维空间中,通过调整游客在长城上的观测高度和视程,将长城沿线风景林划分为视觉盲区、视觉感知区、视觉敏感区3个类型,结合研究区植被、森林起源等专题图数据,采用空间叠置分析法,获得新的区划斑块,从视觉感知方面客观确定每个风景林景斑类型,为八达岭长城风景林科学经营提供科学依据。结果表明,八达岭长城风景林区在最远2 000 m视域范围内,视觉盲区、视觉感知区、视觉敏感区面积824.44 hm2、880.4 hm2、3 247.77 hm2。空间叠加分析将八达岭长城风景林区分为119个风景林景斑类型,为了经营管理方便,划分10种大的类型,分别是视觉敏感区保安灌木林、视觉敏感区保安林、视觉感知区保安林、视觉感知区保安灌木林、视觉盲区保安林、视觉敏感区观光林、视觉感知区观光林、视觉盲区观光林、视觉敏感区游憩林、视觉感知区游憩林。

The scenic forests along the Badaling Great Wall（BGW） is 2 227.8 hm2,with a forested area of 1 314.2 hm2.The configuration and management of the scenic forests along BGW are important elements of the scenery.In this study,spatial viewshed analysis on ERDAS virtual GIS platform was used to configure the scenic forests along BGW.First,the scenic forests along BGW and a ＂tourist＂ were put in a virtual three-dimension space.The ＂tourist＂ viewed the scenic forests from 35 observation spots of different coordinates.The view ranges of the ＂tourist＂ were divided into three levels — close range（0~500 m）,moderate range（500~1 000 m） and long distance（1 000~2 000 m）.Then the view range and inter-visibility of the ＂tourist＂ at the three view range levels at every observation spot were recorded.Based on the view results,the scenic forests was divided into vision blunt,perceptive and sensitive areas.The results of the viewshed analysis were overlaid with vegetation and BGW forest origin data to generate a zone map.Then the landscape type of every patch of the scenic forest in the map was determined in terms of view perception.The results showed that the vision blunt area,perceptive area and sensitive area of the scenic forests along BGW were respectively 824.44 hm2,880.4 hm2 and 3 247.77 hm2,respectively,in the farthest view rang（2 000 m）.Through overlay analysis,scenic forests along BGW were divided into 119 landscape patches.For management convenience,the patches were classified into 10 forest groups.The groups included protection shrubbery in vision sensitive area,protection forest in vision sensitive area,protection shrubbery in view perceptive area,protection forest in view perception area,protection forest in vision blunt area,sightseeing forest in vision sensitive area,sightseeing forest in vision perception area,sightseeing forest in vision blunt area,recreation forest in vision sensitive area and recreation forest in vision perception area.The study provided the scientific basis for scientific management of scenic forests along BGW.