(URCA – GEGENAA, Reims, France)

Abstract: In an approach of study of the urban process of Reims, a work of urban morphology associated with a study of historical topography is realized to highlight the driving force of the construction of the urban form. This requires to consitute a reference plane of the preindustrial city, from the Napoleonic cadaster in order to locate the historical and geographical objects which make up the urban space. Finished in 1819 and source document for morphological analysis and regressive mapping, it’s quite geometrically right. However, recalage of this fiscal document with regard to the current maps, revelates few errors. It’s difficult to appraise if these errors indicate internal problems of the document or if they are related to its treatment. So it’s difficult to quantify the share of the one or the other one. But the repetition of certain recognizable errors can allow to esteem the errors of the cadastral survey. After a brief overview of the georeferencing operation (protocol, preparation of raster files), this poster presents the tools met to estimate the topographic quality of the original document (proposing to evaluate the RMS error, methods to compared the squares forms with the current cadaster). Thus, thanks to the entities created from the vectorization of the cadastre of 1819, the orientations of the fragmented, the forms and density plots are then treated statistically and a checklist of control points is then established for the georeferencing of historical maps.

Keywords: historical map, georeferencing, spatial analysis