The International Hydrographic Organisation (IHO) has determined the guidelines and specifications to achieve an international series of nautical charts. The purpose of having an international series of nautical charts is to ensure minimum coverage of the world seas and adjoining waters and straits.
A valuable by-product of IHO is that it is a relatively effortless process to exchange data, in relation to printing international nautical charts.
A large number of the nautical charts published by the Danish Geodata Agency are part of the international series of nautical charts. These charts have a system of double numbers, one Danish number and one international, marked with INT XXX.
All the Danish charts are bilingual, meaning that all text crucial to the safe passage is in both Danish and English.