The governor's house at Edinburgh Castle has been identified as the birthplace of the modern map by Historic Scotland's principal historian.
It was here that William Roy, father of the Ordnance Survey, and Paul Sandby, who was a major influence in British watercolour painting, are believed to have collaborated on their first map-making enterprise in the 1740s. From this flowed the surveys that are the essence of the maps, road atlases and street plans that are vital to so many aspects of modern life.
Chris Tabraham, Historic Scotland's principal historian, said: "We know that Roy spent his summers in the field with the survey teams, then headed back to Edinburgh Castle, where the maps were made. But that begged the question of where in the castle they worked. Find that and you find the spiritual home of OS and all that has resulted from the remarkable work it has done for more than 200 years."
Dr Tabraham researched the issue after being invited to contribute a chapter for The Great Map, a recenly published volume that convenes for the first time all the maps Roy and Sandby produced at the castle. He has put together clues which point to the governor's house - which incorporated the lodgings of the storekeeper and the master gunner - as the most likely location.
www.nls.ukmapsindex.html. The Great Map: The Military Survey of Scotland 1748-55 (Birlinn pound;200).