The British Cartographic Society

The British Cartographic Society (BCS) was formed in 1963, and since then map-making has undergone a revolution, from land survey using theodolites to digital survey using satellites. But the infrastructure for the old ways still exists and the most recent issue of Maplines, the BCS membership magazine, calls for Ordnance Survey benchmarks to be given greater protection. Cut into stone at the base of a building, church, or bridge, benchmarks consist of a horizontal bar above an upward-facing arrow. The height above sea level of every benchmark is known, so surveyors can use this to find the elevation of any other point above or below that of the benchmark using a theodolite and a mea