This paper presents how the research program PORTIC takes into account the uncertain character of historical data pertaining to eighteenth-century maritime trade to qualify and subsequently to visualize it. More specifically, we deal with the representation of ships’ calling at a French port. We collected clearances’ or arrivals’ declarations into a database called Navigocorpus which was elaborated a decade ago, and enriched with new data since. Missing data, but also patently incoherent paths induced us to elaborate a series of variables to qualify their degree of uncertainty and propose different scenarii, which we represent thereafter in space and time in a legible form.