Map produced by the Ordnance Survey at the 6 inch to 1 mile scale. The work to produce the 3rd edition did not involve the full re-survey of the land, but was rather a revision of the 2nd edition map, only looking at areas where significant changes to land use had occured. The map sheets for Lincolnshire were published on an ad hoc basis, between 1907 and 1950, with the exact date of publication marked on each separate sheet.