GSGS series 4414. Sheet 2317, Second Edition (A.E.F.). First edition copied from German Topographische Karte 1:25,000 Sheet 2317 dated 1936 and photolithographed by the British Ordnance Survey in 1944. Second edition revised from air photographs January 1945 by 21 A. Gp. Air Survey Group. Lambert modified conical orthomorphic projection. Nord de Guerre Grid.