The International Hydrographic Organization (IHO) was established in London in 1919, being based in Monaco since 1921. The World Hydrography Day (WHD) is celebrated every year on 21 June. The International Hydrographic Organization and its full members (94) celebrate this day through various actions with the aim of raising awareness of importance of hydrography in many sea-related activities. Special attention is given to activities that increase the coverage of sea areas with high-quality hydrographic data, as well as initiatives and joint projects whose results contribute towards the safety of navigation, protection of marine environment, planning of coastal zone management, implementation of a marine spatial data infrastructure, and use of new technologies in hydrography.

In preparations for the celebration of WHD, the IHO member states are invited to propose a theme to be the common IHO theme of the year. To mark 100 years since the establishment of the International Hydrographic Bureau (IHB) in Monaco on 21 June 1921, which was later renamed the Secretariat of the IHO (IHO Sec.), this year’s theme is “One Hundred Years of International Cooperation in Hydrography”. The theme is intended to show the progress in knowledge and technology over the past 100 years, and at the same time to highlight the most important achievements in that period, advances in technology and state-of-the-art technology. Although at the IHO level an eventful programme was planned to mark the 100^th anniversary, this had to be significantly reduced due to the COVID-19 pandemic. However, a few events that will take place in Monaco will be available to member states and the wider public via video streaming and virtual panel discussions.

Hydrographic Institute of the Republic of Croatia issues a press release on the occasion of the World Hydrography Day 21 June 2021 and 100 years of international cooperation in hydrography.