以数据量节省和粒度精细为目标,提出了一个面向对象的多尺度概念模型——尺度空间中GIS数据表达的生命期模型。该模型认为,GIS数据在其表达空间中不同的尺度点和尺度段上分别产生突变和缓变的交替变化,其尺度变换过程可描述为三元组Ti:〈[si1,si2],fi,{gij}〉,其中[si1,si2]为尺度范围,fi为作用于[si1,si2]的变换函数,{gij}为[si1,si2]尺度范围内的表达基态。则任意尺度点的表达可形式化地表达为:Rx=fi({gij},x),x∈[si1,si2]。并总结了4种尺度变换模式:地图综合尺度变换、LOD尺度变换、Morphing尺度变换和等价尺度变换。
Multiple representations of spatial data,which means obtaining different detailed representation of geographic phenomena based on the same spatial database or different data versions,is one of the key technologies in GIS applications.It plays an important role in such applications as seamless data navigation,progressive web transfer and self-adaptable visualizations.This paper aims at the objective by small size of data volume to realize high granularity multi-representation,presenting an object oriented data model,namely the lifespan model over scale space,to divide the spatial data into different representation scenes over scale space.The scale transformation is represented as Tij: fi,[si1,si2],{gij} ,where fi is the transformation function,[si1,si2] the scale range controlled by two key scale points si1 and si2 and {gij} the base representation status associated with the key scale point of si1 or si2.Then the representation at any scale point can be represented as: Rx=fi({gij},x),x∈[si1,si2].The study summaries that there are four transformations,namely map generalization,LOD accumulation,morphing and equal transformation.