Study on Urban Spatial Expansion and External Morphology Evolution Based on RS/GIS:A Case of Huai'an City

In the case of Huai'an city,this paper examines urban spatial expansion and external morphology evolution.GIS approaches are used to analyze and data sources from remote sensing images and urban built-up area status map.There are some findings as follows: first,urban spatial expansion is characterized by phase and anisotropy.Before the year of 1965,urban space grows slowly,mainly expanding to north and northwest direction.From the year of 1979 to 1995,the urban space grows by high-speed,and the dominant direction turns to the northwest and southwest.Since the year of 1995,urban space grows faster than before and the dominant expanding orientation is east and southeast.Second,Urban spatial expansion model can be summarized as three types,including the type of slow expansion by wing,the type of circle progressive expanding and the type of rapid expansion by wing.Third,the paper calculates the compact index,fractal dimension and shape index,finding that the urban spatial form of Huai'an city is relatively stable.Moreover,the urban form changes from star shape to block shape,and obvious tends to round.Last,the study also finds that the characteristics of stage and anisotropy have significant effects on the evolution of urban external morphology.