1. A method of relating local data maps for forming a composite global data map, comprising steps of: evaluating overlapping regions of local data maps to define a plurality of difference maps; fitting a set of parameters to the difference maps to quantify initial differences between the overlapping regions of the local data maps; defining a corresponding set of parameters that can be varied in value for altering orientations of the local data maps; and solving linear equations to determine the parameter values of the local data maps that satisfy a merit function incorporating the parameter values of the difference maps.