GSGS series 4228. First Edition. Italian Istituto Geografico Militare map dated 1929 and photolithographed by the British Ordnance Survey in 1943. The graticule on this sheet is on the French system. To convert to the Italian system deduct 1.5 seconds from the French latitudes and 8.5 seconds from the French longitudes measured from Greenwich. Contours at 25 metres (V.I.). North Italy Grid.