A well-suited approach to calculate the fractal dimension of digital images
stems from the power spectrum of a fractional Brownian motion: the ratio b
etween powers at different scales is related to the persistence parameter H
and, thus, to the fractal dimension D=3-H. The signal-dependent nature of
the speckle noise, however, prevents a correct estimation of fractal dimens
ion from synthetic aperture radar (SAR) images. Here, we propose and assess
a novel method to obtain D based on the multi-scale decomposition provided
by the normalized Laplacian pyramid (LP), which is a bandpass representati
on obtained by dividing the layers of a LP by its expanded base band and is
designed to force the noise to become signal independent Extensive experim
ents on synthetic fractal textures, both noise free and noisy, corroborate
the underlying assumptions and show the performances, in terms of both accu
racy and confidence of estimation, of pyramid methods compared with the wel
l-established method based on the wavelet transform. Preliminary results on
true SAR images from ERS-1 look promising as well. (C) 2001 SPIE and IS&T.