The smoothness estimator, , needs to be measured from the residuals of the linear model fit. This estimator explains the spatial correlation structure of the SPM by assuming that it can be modeled as being due to a convolution of the (white) real signal with a Gaussian filter with an unknown, but determinable, width. Calculating the width of this Gaussian allows us to determine the effective resolution of the data.

David Flitney 2001-11-29