GSGS series 4228. First Edition-AMS 1. Italian Istituto Geografico Militare map dated 1931 and photolithographed by the British Ordnance Survey in 1943. The meridians are based on the meridian of Rome, which is 12 degrees, 27 minutes and 7.1 seconds east of Greenwich. Contours at 25 metres (V.I.). North Italy Grid.