Modeling the transformation of France's postal exchange space (1632–1833) through multipolar anamorphoses

Multipolar anamorphoses constitute a classical way of representing major spatial changes due to innovations in transportation systems. They are, however, rarely used for historical periods due to the lack of precise sources concerning transport speed and infrastructures. Starting with a historical geographic information system (HGIS) model integrating post houses (or coaching inns) and roads in France for seven dates from 1632 to 1833, we modeled historical distances by taking into account a multigraph of pedestrian trajectories and postal roads, with edges weighted by the intensity of slopes and the evolving speed of horse travel. Indeed, due to major improvements in roads and stagecoach construction, average horse speed doubled between 1765 and 1780. The resulting anamorphosis maps show an increasingly distorted map of France, with a shrinking of space north of a Rennes-Geneva line associated with low relief, and a massive dilation of higher mountain ranges and fragmentation around a multiplication of speed archipelagos in southern France. We interpret this evolution as the replacement of France's pedestrian mobility regime by a new horse mobility regime. As the exchange of information through the postal service accompanied the exchange of goods and trade between merchants in different cities – which expanded greatly during the 18th century at a time of colonial maritime trade – this result suggests that a speed revolution took place in France one century before the invention of the railways. • From 1632 to 1833, we modeled historical distances with postal roads. • We take into account both pedestrian trajectories and road's network. • We consider improvements in roads and the evolving speed of horse travel. • New resulting anamorphosis maps show distortions in France.