A method, apparatus and computer program code for processing data from potential field surveys, particularly airborne gravity field surveys, to correct for the effects of terrain. A method of processing potential field measurement data from a moving platform survey for mapping a field includes data defining a time series of potential field measurements captured by a potential field measurement instrument mounted on a moving platform, each of the measurements having associated data defining positions, inputting terrain data defining a spatial variation of terrain surveyed, determining time-domain correction data to be applied to the measured potential field data in the time-domain, and adjusting the measured potential field data defining the time series of potential field measurements using the time-domain correction data to provide terrain corrected measured potential field data for the mapping of the field.