空间数据的多尺度表达是当代GIS研究的热点问题之一。该文针对矢量数据快速可视化的需求，结合制图综合领域的相关理论，提出了一种矢量数据双层次多尺度表达模型，用来将矢量数据抽象为空间要素和要素内的点坐标两个层次进行表达。其中空间要素层次的表达以空间要素为最小研究单元，通过建立多尺度索引来描述空间要素因尺度改变而引起的数量或性质变化；要素点坐标层次的表达则是以要素内坐标点为最小研究单元，通过尺度层次标记的方式来表达空间要素内的点坐标随尺度变化的渐变过程。该模型在开源数据库管理系统PostgreSQL支持下，扩展了相应的索引与函数，实现了矢量数据的双层次多尺度表达模型，同时设计了相应的检索算法，并以某城市1:10 000土地利用数据为例，对上述模型与检索算法进行了验证。实验结果表明，在基本不影响可视化效果的前提下，该矢量数据多尺度模型能极大地提高海量矢量数据的可视化与传输的效率。

Multi-representation of spatial data is one of the hot topics in modern GIS. This paper proposed a bi-hierarchical multi-scale model to represent large vector data with two hierarchies, namely spatial elements and vertex coordinates, so as to improve the visualization efficiency. Firstly spatial elements were taken as the minimal units and organized with a multi-scale index to describe the changes of quantity or property of elements brought with scale changes.Then vertex coordinates were regarded as the minimal units and tagged with scale hierarchy labels to describe the geometric changes arising from different scales. Under the support of PostgreSQL, this paper implemented the bi-hierarchical multi-scale model by extending the index and functions, and developed the searching algorithms. Finally, a 1:10,000 scale land use dataset was taken as an example to validate the model and searching algorithms.The results showed that the visualization and transmission efficiency of large vector data could achieve great improvement with the proposed model and searching algorithms.