As a secondary option available from the PRO, one can copy the map on microfilm onto paper, if one is lucky enough to find the map one is interested in on microfilm. This introduces two sources of distortion; firstly, the method of capture used in the first instance is unknown and secondly the distortion introduced by the microfilm reader is indeterminable. In all the above cases the maps have to be registered to a co-ordinate system, as none was used in the creation of the tithe maps. This can be done by comparing features in existence on registered maps and creating points to register the maps to.