[Changes of characteristic scale of Nanjing urban landscape]

Based on 3 scenes of Landsat TM image taken in 1988, 1998 and 2006, the changes of the structural characteristics of Nanjing central urban area were studied with one-dimensional wavelet analysis. The results showed that it was necessary to select an optimal sampling width when using wavelet analysis to detect the characteristic scales of landscape transects. Too narrow transects could cause lack of stabilization, while too wide ones could cause loss of some minor characteristic scales. From the TM images (30 m resolution) of Nanjing urban area, the optimal sampling width was identified as four pixels. The results from one-dimensional wavelet transform indicated that the landscape of Nanjing central urban area had four relatively stable characteristic scale domains in 1988, 1998 and 2006, corresponding to functional clumps, small blocks, middle-sized blocks, and large blocks, respectively. From 1988 to 2006, the scales of large blocks were nearly unchanged, while the other three domains all changed significantly with a similar trend. Moreover, the variations among the characteristic scales within each scale domain declined from 1988 to 2006, indicating that the landscape structure of Nanjing central urban area tended to be more stable and accordant. The scale domains showed synchronous changes as well.