Large-scale land use by remote sensing - Franco-Valdo-Genevois test batch

CEREMA worked in 2013, as part of an exploratory study for the DREAL Rhônes Alpes, the DRAAF Rhône-Alpes and the Regional Council of Auvergne-Rhône-Alpes (Auvergne-Rhône-Alpes Region) on the implementation semi-automatic of a first level land cover layer on the territory of the SCOT du Rovaltain from satellite images. The objective of the method is to help the services in charge of territorial planning to calculate the quantified indicators characterizing land use and its evolution in order to meet the regulatory requirements in this area. The layer construction method consists of combining an automatic extraction of information from satellite images (supervised classifications) and post-processed information from existing databases (BD Topo, RPG...). If the construction process differs from the IGN process for setting up the future Large Scale OCS layer, and if the layer specifications are less ambitious, the objective is to have a layer consistent with the national repository. : compatible nomenclature, use of the same structuring skeleton of the territory, same minimal unit of collection etc... The interest of such data lies in the following points: - temporal homogeneity of the source information (the satellite images used - RapidEye images at 5m of resolutions from the GEOSUD program) are acquired on national territory a few months apart; - possibility of annual updating, due to the annual updating of national satellite coverage, and the use of automated processes; - limited costs (satellite images are available free of charge for institutional users, and the automation of processes reduces the human time required for photo-interpretation methods, for example); - response to a first level of needs (zero state of the "natural framework" and "urban framework", quantification of the distribution of urban or natural surfaces, quantification of the effectiveness of various development measures taken, etc. ...) It is divided into 7 classes of ground cover: Man-made surfaces, Transport infrastructures, Bare soils, Water surfaces, Eternal snow and glaciers, Woody vegetation and Non-woody vegetation. The product is delivered in vector format with a minimum collection unit (UMC, size of the smallest polygons) of 500 m². This transition from a 5 m resolution image to a 500 m² UMC implies a generalization of the geometry of the objects represented which is particularly perceptible on the linear elements of the landscape (discontinuity of the road network in particular). When available, usage information is also specified in a raster layer at 25 m². It is divided into 6 classes: Agriculture, Mines and quarries, Secondary production, land or residential use, Road, Rail, Air. The product is delivered by department, according to the area defined in the BD CARTO® (standardization in progress, the department of Drôme having been delivered on the GEOFLA® area).