GSGS series 4228. First Edition. Italian Istituto Geografico Militare map dated 1932 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. The grid on British Map Series of YUGOSLAVIA, which adjoins the Eastern edge of this Series, is computed on the geographicals of the Greek datum. To convert Greek geogrpahicals to the Italian, upon which the grid of this map is based, subtract 2.5 seconds from the Latitudes and add 10.5 seconds to the Longitudes. Contours at 10 & 25 metres (V.I.). North Italy Grid.