Provisional GSGS series 4229. Second Edition-AMS 2. Copied from an Italian Istituto Geografico Militare map dated 1931 with principal communications revised using smaller scale maps from 1938 and air photos from 1943. Compiled by the U.S. Army Map Service in 1944. Road classification is NOT based on reconnaissance, reliability is uncertain. The grid on map series which adjoin the northern edge of this series, is computed on the geographicals of the French datum. To convert French geographicals to the Italian, upon which the grid of this series is based, subtract 2.8 seconds from the latitudes and 8.1 seconds from the longitudes. The meridians are based on the meridian of Rome, which is 12 degrees, 27 minutes and 7.1 seconds east of Greenwich. Contours interval 50 metres. North Italy Zone Grid.