Abstract

In 1747 Louis XV commissioned Cesare-Francesco Cassini of Thury to draw up a «general and particular» map of France, a general portrait of the kingdom, which would also provide detailed information about local spaces. Black and white or pastel colored, the 182 sheets that make up the Cassini collection are of rare beauty. They also constitute a precious historical source for the observation and study of different landscapes in 18th century France. Over a short number of years, the collaborative vectorization project geohistoricaldata.org has allowed the digitization of the whole road network, of cities and villages and, for some areas, of the entire set of data collected by Cassini's cartographers. Thanks to this work, it has become possible to compare the forms and structures of the old landscapes with those of our present. To make such a comparison, however, it is necessary to better understand the status of the measurements at the origin of the maps and their relationship with the old spaces and objects represented. I tried to answer these questions by combining a series of live monitoring visits to local landscapes with the representations given by archival evidence and by maps drawn at different periods and at different scale levels. The following pages are extracted from the research diary I kept during the first monitoring trip carried out in the Clermont-Ferrand district during the summer of 2015. They illustrate the questions and the difficulties posed by local archive sources and direct observation in the building of such an approach. They also illustrate some of the possible answers.