Two systems of bilinear interpolation were studied in deriving a procedure for transforming geo-referenced grid locations to locations on maps defined by digital image column and line coordinates. Map data were from 1:50,000 UTM topographic charts, where digital data were from SPOT satellite data processed to level 1b corrected for earth rotation and curvature and off-nadir viewing but without local control. Two independent data sets gave similar results. Procedures for collecting and alalyzing control data are presented and trial models are shown and discussed.