Naval freedom of action rests on information that few outside the profession ever see. Before a frigate can operate close inshore, before an amphibious force can choose a beach or a mine-countermeasures group can clear a channel, someone must have measured the seabed, checked the measurements, turned them into charts and kept those charts up to date. In Europe that work is being transformed. Uncrewed surface and underwater vehicles now collect far more data than the survey ships they supplement; production software is being automated; and a new international data standard, S-100, is changing how hydrographic information is modelled and exchanged. These changes raise a question that matters to governments, navies, investors and suppliers alike. If the vehicles, instruments and software that produce hydrographic information come from a mix of national, European and non-European companies, does a European state still control the information on which its navy depends? France offers a particularly instructive case, because a single public establishment exercises the State’s hydrographic functions and supports defence while it renews its acquisition means, rebuilds its production chain and prepares for S-100. The question is whether France retains the functions needed to generate, assure, update and authorise hydrographic information when individual industrial inputs are supplied by third parties, and what that answer implies for the way Europe should measure autonomy in this field.