Maritime history archives contain a large number of toponyms whose meaning is sometimes difficult to grasp. They are lacunary and not quite homogeneous like most of historical datasets. The PORTIC project (https://anr.portic.fr/) intends to take into account the imperfection of these kind of data to answer questions on shipping activities in French ports and French foreign trade at the end of the eighteenth century. This paper focuses on the geographic dimension of data imperfection, and how it was handled to build datasets and tools useful for historian community. The first part shows how we have dealt with these problems to build and publish online a gazetteer of French port places of the 18th century, linked with GeoNames, by using the model LinkedPlaces defined by the LinkedPasts initiative [1]. The second part discusses the requirements for a vectorial background layer made of polygonal territorial entities valid for 1789, and how it has been addressed by the project, and challenges that remains to be overcome.