1. A computer-implemented method of processing a set of measurements of geophysical data including at least measured potential field data from a potential field survey of a surveyed region of the earth to provide a representation of the geology of said surveyed region with a data processing system, including a processor, the method comprising: using said processor, generating a shallow earth model of said surveyed region by fitting data predicted by said shallow earth model to said measured potential field data for a pre-defined bandwidth of the measured potential field data by applying 
 min{ L [filter(pred( x )− m )]} where filter is a spatial filter to remove frequencies outside a range of interest, L is a fit measure, pred(x) are the data predicted by the shallow earth model given a set of parameters x, and m represents the set of measurements; predicting full range potential field data for all measured frequencies using said generated shallow earth model; comparing said predicted full range potential field data to said measured potential field data to provide full range residual data representing a difference between the predicted full range potential field data and the measured potential field data, and interpreting said full range residual data to provide a representation of said geology of said surveyed region.