The analysis of the evolution of transport networks can be performed by methods from graph theory or network theory, for example by modelling the growth of the network or by analysing the evolution of global or local indices over time. However, this approach requires geographical databases representing the networks at different times. Maps are a natural source to create, by vectorisation, such geographical databases. This article shows that, because of the particular nature of the cartographic representation that is a model of the territory rather than a mere image, it is necessary to explicitly take into account the modelling relation at the time of the map to be able to distinguish between the evolution of the territory and the art of the cartographer, rebuilding thus a kind of critical apparatus of the map.