【摘要】 制图实体在制图综合中随尺度发生变化,描述变化的基本元素包括状态与事件。目前基于层次的多尺度表达模型侧重于状态表达,忽略了引起状态变化的事件。该文探讨尺度参考系、尺度事件等基本概念,提出基于PetriNet的多尺度表达模型,分别用PetriNet的库所、变迁与弧描述制图实体的状态、事件与关系,通过实验分析该模型的优点。更多还原

【Abstract】 Multiple representations of the same GIS features for different map scales or for different map products are issues that concern many mapmakers.The really hard work is in establishing and managing the relationships between the derived cartographic representations of features and their source GIS features.Scales in geography can be interpreted in two aspects,the comparative size and the abstract level,while scale is described as "map scale" in cartography.Scale dimension is continuous as time dimension and can be depicted by a reference system,i.e.scale dimension,scale origin,and scale value.The cartographic entity,as element of a map,may have different representation instances at different scales.While the same cartographic entity is represented at different scales,its representation instances may change in spatial location,shape and type,which evoke events such as classification,simplification,exaggeration.A basic requirement for cartographic database is to provide representation instances of the same cartographic entity at different scales and also to relate them with each other.This paper is intended to focus on representation instances,and make research on their states,scale events and correlations between these states and events.Petri Net has place,transition,and arc as its elements,which are respectively used to describe states of a representation instance,its scale events,and relations between these states and events.In this way,not only a multi-scale map is represented,and the topology between scale zones can also be clearly represented.When it comes to the multi-scale hierarchical model,its scale variable can only choose some specific scales,while in the Petri Net-based multi-scale model,this scale variable can make continuous changes in the valid scale ranges,providing theoretic bases for the implementation of a continuous scalable map. This model which organically associates states,events and their relations with each other,can implement queries based on states,events and relations,and also is tailed to both multi-scale based analyses and data update applied in GIS and cartographic databases.更多还原