The aim of the research presented in this paper was to determine the precise location of drop zones that were used for parachute jumps of the ‘Silent and Unseen’ paratroops (Polish: Cichociemni) and for delivering military equipment during World War II. The studies were based on historical research containing information about the locations of the jumps and their schematic arrangement, Ordnance Survey Maps of the pre-war period, and a GIS system with contemporary geographic digital maps. Within the work, the available information about the drop zone locations of the period from February 1941 to December 1944 is summarized. Moreover, the calibration of available schematic maps is presented, based on contemporary digital data. The final part of the study contains an estimation of drop zone location errors compared against military tactical maps.