Institut Géographique National

Diadeis Mission IGN (the National Geographic Institute) is commissioned by the state to produce geographical data for the national territory and make this available to the public (in the form of maps or electronic files as well as on its internal Geoportail site). In 2001, IGN was asked to set up a large scale digital database ("RGE") covering the whole of the country and comprising four digital components that are complementary and consistent: • colour orthophotographs (BDORTHO® by IGN), • topographical database (BDTOPO® by IGN), • address database (BDADRESSE® by IGN), • and a component containing landholding information based on a digitised cadastral map, named BDPARCELLAIRE®. To draw up the landholding component, a geographical database needed to be set up which attaches DGI (Tax Office) cadastral data to the IGN's geographical data. This involves in particular: • linking the cadastral map to the national grid coordinate system • achieving the best possible data continuity • ensuring consistency between this data and that of the topographical and orthophotographic components from the RGE • integrating updated information on the cadastral data supplied by the DGI (plots and buildings) IGN has committed to finishing BDPARCELLAIRE® by the end of 2007 and has entrusted DIADEIS with 25 geographical departments, the yearly updates being carried out internally.

Technology • Use of GeoTexel technology for georeferencing • Automatic georeferencing using GeOCR technology developed by DIADEIS • Fine tuning of operator interventions and automatic batch processing using a workflow system • Production control using CAPM (Computer Assisted Production Management) • Centralised management of metadata in a database • Continuous management of plot database blocks in a centralised database

Human resources • Input data checking and preparation • Vectorial data input • Georeferencing • Geographical adjustment and matching • Link processing • Conformity checking • The production staff is encircled by production management, the development team, and trade specialists

Volume 2005: 4 departments for a total of 21,952 sheets. 2006: 21 departements for a total of 109,728 sheets

Main challenge • Relate the cadastral map to the national coordinate system • Provide the best possible data continuity • Ensure consistency between this data and the topographic and orthophotographic components • Integrate cadastral data update information

Input The plot image database is produced from scanned images of cadastral maps supplied by the DGI and from orthophotographs supplied by IGN.

Output A digital georeferenced representation on the French cadastral orthophotograph.

Result IGN now has a new database of French territory. This information is especially useful to local authorities in their town planning. Thanks to DIADEIS, this database has succeeded in being completed quickly at a controlled cost.