Extracting residential information by remote sensing technology is significant for the loss estimation of natural disaster and the study of urban extension and environmental change.In this paper

taking Jiangning county of Nanjing as a case study area

the extraction of re sidential information from SPOT images is discussed.Firstly

the characteristics of residential areas in this area on this image are studied

secondly

spectral characteristics of residential areas and other land-use types on SPOT-4（XI） image are analyzed to find the possibility of extracting residential areas from the background according to spectral characteristics.Thirdly

a simple model of decision tree is proposed on the basis of spectral magnitude relations and some proper thresholds of residents and other land-use types.But some roads still cannot be separated from residential areas because their spectral characteristics are similar.Therefore

their shape characteristics are analyzed.The result is generalized and converted to vector coverage.Then the shape indexes of every spots are calculated and categorized choosing a threshold to remove the roads.Finally

the vector coverage of residential areas is overlaid on the original image to check the effectness of this model

and an accuracy assessment is given to the result by random samples.The results suggest that this model is simple and effective

especially for the residential areas over 10000 m2

and the analyzedfor is much higher than the supervised classification’s

however

some pixels near the water-bodies and the roads are judged by mistakes.This problem can be solved by the rule judgment based on the knowledge of spatial relations.Therefore

the cities

towns and villages in the south of Yangze River where there are various types of land cover can be extracted from the images by this model

and the model is not limited by the time

only the thresholds will be changed.