以环杭州湾地区为研究对象,应用决策树和形状指数相结合的方法从TM影像中分别提取了2003年和2006年的城镇用地信息,并对杭州市、绍兴市和宁波市的城市扩张特点进行了分析和研究。通过精度检验,城镇用地总体Kappa系数都在0.87以上,说明该方法提取城镇信息是行之有效的。2003年环杭州湾地区的城镇用地面积为914.04km²,2006年为1 286.1km²,4年间城镇用地净增了372.06km²,主要城市用地净增了192.6km²;杭州市、绍兴市、宁波市市区面积增加了43.7 km²;而其它县城与开发区增加了145.6 km²;说明小城市在环杭州湾地区城市化进程中处于主导地位;而大城市的作用则相对较小。杭州市、绍兴市城市扩张明显,其中尤以杭州市下沙区和绍兴市袍江工业园区的扩张最显著;宁波市城市扩张最小,特别是余姚城区。扩张方向上,杭州市主要向西北和北面扩张;宁波市在各个方向上的扩张比较平均。

Taking the region around Hangzhou Bay as a study area, the urban land information was extracted from TM images of 2003 and 2006 through the decision tree method together with the shape index. And the characteristics of urban expansion in cities of Hangzhou, Shaoxing and Ningbo were further discussed. The overall Kappa coefficients of urban land were all above 0.87 through precision test and proved that: it was feasible to extract the information of the urban land. The area of urban land in 2003 and 2006 was 914.04 km² and 1286.1 km² respectively. A net increase of the urban land in the study area within four years was 372.06km², and the number was 192.6km² in the major cities; the increase of urban area in Hangzhou, Shaoxing and Ningbo was 43.7 km²; and that of the others was 145.6 km².It revealed that the small cities played a dominant role in the process of urbanization, but the bigger cities’ were relative weak. The urban land in Hangzhou and Shaoxing expanded obviously, and especially the expansion of Xiasha district in Hangzhou and Paojiang industrial park in Shaoxing were more remarkable. However, the smallest expansion occurred in Ningbo, especially in Yuyao urban district. In expansion direction, Hangzhou urban districts mainly developed toward northwest and north; while Ningbo urban district spread in all directions evenly.