A method of processing 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, the method comprising: inputting a first and a second set of measured potential field data wherein at least said first set of measured potential field data is filtered data; and generating a model of said surveyed region by predicting a first set of data and a second set of data corresponding to said first and second sets of measured potential field data; filtering said first set of predicted data, wherein said filtering matches the filtering applied to the first set of measured data and fitting said first set of filtered predicted data and said second set of predicted data to said first and second sets of measured data, respectively.