An extension to the wavelet- based method for the estimation of the spectral exponent,gamma, in a 1/f(r) process and in the presence of additive white noise is proposed. The approach is based on eliminating the e. ect of white noise by a simple di. erence operation constructed on the wavelet spectrum. The. parameter is estimated as the slope of a linear function. It is shown by simulations that the proposed method gives reliable results. Global positioning system ( GPS) time- series noise is analyzed and the results provide experimental verification of the proposed method. Copyright (c) 2007.