Canevas – Tours Métropole Val de Loire

**The topographic canvas is a set of topographical support points of high precision used as a reference to surveyors, topographers for field surveys.** It makes it possible to meet the obligation to link all topographic operations to the legal reference system **RGF93**. These points are materialised in the field, calculated in XY coordinates (**projection CC47**) and Z (**NGF-IGN69**), identified on MSDS and made available to all. It covers the entire City of Tours. Some points can also be found in the communes of Saint-Cyr-sur-Loire, Saint-Pierre-des-Corps, La Riche, Joué-lès-Tours and Chambray-lès-Tours. It consists of 25 pairs of primary points (ex: P15001) calculated by GPS in post-processing, and 919 secondary points (e.g. S15051) calculated by traditional method. HOW TO RECOGNISE A POINT IN THE CANVAS? The landmarks are most often materialised by a survey nail and a CAT-engraved washer sealed at the edge of sidewalks and by terminals in non-urbanised areas.