The first privately produced map in Norway with a geodetic reference frame

A map of the district surrounding the largest lake in Norway was published in 1796 by the Topographical Society of Norway. Their members contributed private funds for this unique map and for the publication of the Topographical Journal, containing multidisciplinary descriptions, including environmental, of many regions of the country. The map was produced by lieutenant Niels S Darre, a military surveyor and cartographer, as a private undertaking in his own home district. The geodetic reference point of the map is the church at Vang, the position of which had been determined by repeated astronomical observations by its vicar, Abraham Pihl. He had been trained as an astronomical observer by professor Thomas Bugge at the Round Tower Observatory in Copenhagen. A supporting latitude determination in Lillehammer is also noted on the map, obtained by Maximilian Hell in 1769 on his return from Vardø in Northern Norway to Vienna after a successful observation of the transit of Venus. The observed magnetic deviation from astronomically determined north is given. The map also identifies a marker of the great flood of the river Glomma in 1789, causing environmental and social devastation. We have digitized the map and compared it to a 67 km × 82 km section of a modern, digitized topographical map of Norway, by transforming the UTM projection to a meridian through the church at Vang. While most features coregister acceptably by visual inspections of the old and new maps, we note geometrical deviations of up to 1 km in the locations of western shorelines