Of course, map dowsing requires a map and when I see a map in film, I always wonder whether it is a real or fictional map of a real or fictional place. Well, in this case it is a real map of the Niagara Gorge. The map is a 1912 topographic map produced cooperatively between the Geological Survey of Canada and the United States Geological Survey (close-up below).
A copy of the map resides in the University of Toronto's Map Library [link] and has been enabled for digital access [link]. It seems reasonable to suggest that the map seen on screen is a copy of UT's, especially considering that the show is filmed in Toronto.
