Multiscale image analysis method for urban applications

Urban is composed of different critical levels of organization where interactions are stronger within levels than among levels, it is a complex system. Image analysis performed at a unique scale for urban applications is doomed to be incomplete and misleading. This paper presents a multiscale image analysis method based on wavelet transform and watershed transform for urban system. It performs image analysis on multiple scale images, and can catch comprehensive information of urban system for different applications. The procedure consists of three main steps: multiscale representation, image segmentation, post-processing. First, multiscale represent creates multiresolution images using a wavelet transform and a modified inverse wavelet transform; a smooth and multiscale presentation of original image is provided. Second, image segmentation segments the multiscale images using watershed segment algorithm. Finally, post-processing merges over-segment regions and smoothes watersheds, then, multiscale image objects are attained. This study was conducted in Nanjing, Jiangsu province, China, using IKONOS satellite data. Experimental results demonstrate that the proposed method is suitable for describing the complex urban system. Both visual and quantitative methods are applied to evaluation the experimental results, and reveal the relation of objects within and among levels.