There are different free sources of Official Nautical Charts, usually each country provides the official charts for its territory, but in some cases there is one source for a group of countries. These sources usually store the nautical maps in vector formats, such as ENC and RNC.

Electronic Navigational Charts (ENC) are vector data sets that support all types of marine navigation. Originally designed for large commercial vessels using a sophisticated navigational computer called an Electronic Chart Display and Information System (ECDIS), ENCs are now also being used on simpler electronic chart systems and “chart plotters” on many types of ships and by recreational boaters [NOAA ENC]. 

Raster Navigational Charts (RNC) are vector data sets used for marine navigation.

The following table shows some of the Official Nautical Chart Sources: