Y. Liu, Y. Zheng, G. Li, S. Li

Department of hydrography and cartography, Dalian, China



With the spread of GIS application field continually, an exigent demand has been produced that is analysis and display the multiple scale spatial data, and it has become the key problem in GIS. In order to realize the true multiple representation of spatial data, we can solve it only by map automatic generalization thoroughly. This paper researches the coastline and puts forward the valid way of multiple representation. Simulating human thinking way when they generalized, building the appropriate math model and describing the coastline with graphics, extracting all kinds of the coastline shape information, the coastline automatic generalization will be finished based on the knowledge rules and arithmetic operators. The main contents as follows:

1.Showing the information of coastline shape with math method. We can express the information by building the curve Douglas binary tree directly and vividly. The curve Douglas binary tree can reveal the shape character of coastline not only microcosmically but also macroscopically.

2. Extracting the information of coastline. It concludes the local characteristic point and its orientation, the curve structure and the topology trait. The curve structure can be divided the single curve and the curve cluster.

3. The multiple scale representation of the coastline. By confirming the knowledge rules of the coastline generalization, the generalized scale and its shape parameter, the coastline automatic generalization model is established finally.

The method of the multiple representation of coastline in this paper has some strong points. It is  human’s thinking mode and can keep the nature character of the curve prototype. The binary tree structure can control the coastline comparability, avoid the self-intersect phenomenon and hold the unanimous topology relationship.