This paper discusses how to establish multilayer storage structure and automatically reduce small scale graph from large scale mapping database by theory of changed-focuses Datum Model.
作者通过变焦数据模型原理，探讨如何建立多层存贮结构，将数字地图中的大比例尺地图数据库自动导出小比例尺图形。
The thesis provides systemic designation and exploiting method for the multilayer distributed database and builds a good model for the practical application.
论文给出了比较系统的多层分布式数据库的设计和开发思路，为实际应用开发建立一个良好的模型。
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