----------------------------Original message---------------------------- Roger, You may consider that the 'drawing process' (drawing, printing, and paper quality) allows for an accuracy of 0.1 millimeter. Therefore the 'ground resolution' of such a map is 5 meters. The general formula being a/S where a stands for map accuracy and S for scale. However two other facts need to be taken into account: - first, a map provides a symbolized graphic representation, features are symoblized using lines, point symbols... which implies that something which is initially abstracted by a mathematical line becomes a thick line etc... For example road casings may be 0.2 mm wide. As a consequence cartographic generalization has been applied, which induces a larger ground resolution in some places (you may consider 10 meters on the average, but it may be larger) - second, the scanner accuracy depends on the fact that you scan multiple colors at once (scanning of a paper map), or each color film separately, because the scanners have some limitations. You may need to use a finer resolution when scanning a paper support, or rather a smaller ratio scanning resolution / map resolution. JPhilippe Lagrange IGN-F