Frames of reference are increasingly being used to enable the spatial annotation of textual documents and thus facilitate access to their content and even their spatial analysis. Nevertheless, little work had been done on the extraction of geographical information from texts to feed such frames. The work presented in this article explores the potentialities of indirect spatial information extraction (place names, spatial relationships, etc.) in the texts of the Nautical Instructions produced by the French Marine Hydrographic and Oceanographic Service. The proposed method combines a lexical approach and a linguistic pattern-based approach and is then compared to the main approaches to extracting geographic information in French.