Urban planners and GIS users need to update their land use information in order to design and perform urban planning. Therefore the maps need to be updated regularly. An appropriate approach of updating them is using aerial images. Due to the high resolution of these images, their low cost, and also the possibility of aerial image acquisition in Iran, using aerial images for map updating has been a great concern. In order to update the available maps, the object changes should be understood, and then reconstructed. In this case and according to the properties of large scale maps (1/2000), buildings are very important features to be updated.In this research, a novel method based on Snake’s theory is proposed to detect buildings’ outlines. Also, a different Active Contour Model was used in order to compare the results of the proposed method. DSM and Ortho Images were produced using Stereo images and enough control points, the curve needed to initialize the snake model was obtained from the generated DSM. According to the results, the proposed method in this research provides the completeness of 86.043%, and the correctness of almost 91.124%.