An apparatus (10) for adjusting the calibration of an imaging system to correct for geometric distortion comprises a rotating drum for receiving recording media (17), a plurality of carriages (18) each having an imaging head (16) with a plurality of addressable imaging channels, and a controller programmed with a lookup table, analytical relationship or algorithm that relates corrective adjustments to be made to the imaging of a given imaging head based on the positions of others of the imaging heads. A method is described for obtaining the lookup table, analytical relationship or algorithm. The method has particular relevance to large imaging systems.