Dredging in navigational channels, ports and harbours is intended to help the mariner navigate safely, with enough under-keel clearance. However, charting is not always uniform. To name but a few examples: ‘maintained depth xxm, dredged to xxm’, or just a depth figure in a white-coloured (no depth contours or detailed depth figures) navigational channel, whereby the definitions used by various charting nations is also not uniform.

Hydrographic surveying in the dredging world can be quite challenging. When dredging in navigational channels, dredging too deep means doing too much work, while dredging too shallow means the work has to be redone. Many dredging operations are conducted within a difficult acoustic environment and with a changing and disturbed bottom, but high accuracy is still required of them. The theme-related articles in this issue provide an insight into the variety of hydrographic aspects affecting dredging operations.

Did you know the United Nations General Assembly adopted a resolution on 29th November 2005 welcoming an announcement by the International Hydrographic Organization of "World Hydrography Day", to be celebrated annually on 21st June (the date when the IHO with the name International Hydrographic Bureau (IHB) was established in 1921). I think I can safely say that all hydrographers we will be happy with this recognition of the work they are doing, and will look forward to co-operating with public and private hydrographic sectors to put our profession in the spotlight. We want not only to show the public what we do, but also to attract the attention of youngsters to hydrography.

After all, if there is general awareness of the value of hydrography to society, budgets will be more easily allocated for projects and public organisations like Hos. In relation to this, I’d like to mention the interesting publication Hidromar (in Portuguese) from the Portuguese HO, offering the public general information on products and projects including safety for recreational boaters and surfers. Such a publication brings home to both public and decision-makers the importance of a generally out-of-sight world of hydrography whose results are taken for granted.

You will have noticed that Hydro International has begun an e-newsletter to enable us to inform you more frequently and in more detail than is possible via our printed magazine. If you are not on the list of subscribers, please let us know by e-mailing us at hydro-international@gitc.nl

Our Editorial Advisory Board members serve on a rotational bases, which means that every now and than we have to say goodbye to much-appreciated members; luckily, we can also welcome new ones. This time we have to say good bye to Dr Hideo Nishida, executive director of the Japan Hydrographic Association. Hideo, thank you for all you did for Hydro International.

Last but not least, we welcome a new member to our Editorial Advisory Board. Dr John K. Hall joins us upon his retirement after 35 years with the Geological Survey of Israel. Although retired from this organisation, he will remain very active in his profession (hobby). As a long-term member of IBCM (International Bathymetric Chart of the Mediterranean) and GEBCO (General Bathymetric Chart of the Oceans), John has over forty years experience in ocean mapping and bathymetric compilations of the Arctic Ocean and the Mediterranean, Black, Red and Dead Seas.