Topographical landmarks

Implantation of geodetic points and bounds for the attachment of topographical surveys. * * * The "topographical benchmarks" data of the Department of Hauts-de-Seine is a set of precise topographic points, measured and used during surveying commissioned by the Department. The georeferenced points and terminals are attached to the reference system in force (RGF 93 in Lambert 93 projection, CC 49 in planimetry and IGN 69 in altimetry) with a planimetric accuracy of 2 cm and altimetry of 1 cm. Thus the re-user has a precise coordinate in the official French coordinate systems. **Lexico** GFR 93:French Geodesic Network 1993 - Official geodesic system in France since January 1, 2001 for all public works of more than 1 hectare, or whose longest length is more than 500 m. CC 49: Eighth zone of the Conique Conform projection system adopted in particular by expert surveyors. IGN 69: Managed by IGN, the General Leveling of France (NGF) is a network of altimeter markers scattered throughout mainland France and Corsica. This network is itself composed of two others: NGF - IGN69 for metropolitan France, the "zero level" being determined by the Marseille tide gauge and NGF - IGN78 for Corsica, the "zero level" being determined by the Ajaccio tide gauge.* IGN: The National Institute of Geographical and Forestry Information, formerly the National Geographical Institute. Survey nail marker: large brass nail, with a round head slightly curved and surmounted by a hole, on which appears the words "OGE surveying" (Order of Surveyors Experts). Spit: flat-headed nail made of steel, often with a washer.