France. Service de la carte geologique de France North Decimal Degree 49.8509 South Decimal Degree 49.4913 East Decimal Degree 4.5624 West Decimal Degree 3.6725 Alternate title: Rethel. Relief shown by hachures. Principal meridian: Paris. Longitude is given in centesimal values (100 grades = 90 degrees) .The Service de la carte geologique de la France was integrated to the BRGM to become the only France Service geologique national. Based on "Carte topograqphique de l'etat major."