Pontoise, Cadastre Napoléonien Limit (1815)

The commune of Pontoise is covered by the Napoleonic cadastre in 16 section sheets, all at 1:1250 scale. The sheets have been digitized by the Archives départementales du Val-d'Oise which keeps the originals. Each sheet has been trimmed and then recalibrated in relation to the Bd Topo of the IGN. A reasoned geometric recalibration, based on georeferencing and intended to correct the topometric inaccuracies of the document was carried out with the aim of obtaining a visual correspondence of the objects between the document and the current reference frames (Bd Topo, Open street map, current Cadastre base). The set of 16 sheets was then digitally assembled to obtain a single document offering continuous coverage of the entire municipality. The 16 georeferenced documents as well as the cadastral mosaic are distributed in the form of a georeferenced file in the WGS84-Pseudo Mercator (EPSG3857) projection system in JP2000 format (downloadable document) compatible with most spatial data management tools or in the form of data streams that can be integrated directly into these same tools. The Napoleonic Cadastre is a mapping operation decided in 1807. It was the first systematic operation on a French scale, with the objective of "measuring more than one hundred million parcels, classifying them all according to the degree of fertility of the soil, evaluating the taxable product of each of them, and gathering the parcels that belong to each owner" (Gaudin Law 1807). This vast and highly codified operation (cadastral code of 1808) was completed in the 1850s. For each commune, registers and an atlas composed of sheets at 1:250 (sometimes 1:500 or 1:200) referencing all of the land entities was executed. The Napoleonic Cadastre is a reference document for the study of pre-industrial spaces since it records the state of development of the territories at the beginning of the 19th century and is, by its overall topometric quality, generally quite accurate geometrically. It is also systematic in its content: plots, roads, odonyms, toponyms, hydrological network, buildings... etc. It can therefore easily be set in a current reference frame with margins of error that are sometimes small (these margins generally depend on the topographic environment: the rougher the territory, the less accurate it is. For Pontoise, the overall margin of error is about 2 m). Its qualities also make it possible to make the link with older documents whose shapes, often still present in the cadastre, can be transferred at sight into the geometric space of the Napoleonic period, which is itself easily "calibrated" in a current geometric space. This document has been vectorized manually (L. Costa) to be able to be processed spatially. A transformation was also carried out to obtain a layer on the parcels and their status, namely: built, light built, communication, Hydro, Parcel