New standards for hydrographic surveys


In late 2020, the International Hydrographic Organization (IHO) published the sixth version of the international standards for hydrographic surveys, IHO S-44. The new version has been expanded to include the possibility to customise hydrographic surveys according to the intended use of the data.

A highly detailed outline of a wreck, generated by a multibeam sonar.

Today, the seabed can be mapped in great detail by using surveying equipment such as a multibeam sonar to determine water depth.  The new standard for hydrographic surveys gives users far more freedom to choose the level of detail they need while also benefiting from the new technological advances in hydrographic surveying.

Hydrographic surveys can now be specified into several different categories via a new matrix approach, allowing the user to customise their requirements for position accuracy, depth measurement accuracy and rendering of objects on the seabed, for instance.

New ‘exclusive orders’
The new standard also introduces a new category, namely the so-called ‘exclusive orders’, which can be used in critical areas where objects with a height as low as 0.5 m need to be detected. Such areas include harbour entrances and artificially maintained fairways/channels, where some ships have a draught that brings them close to the seabed.

The high level of detail in such surveys can also be utilised for construction projects, e.g. in connection with designing offshore wind farms and other facilities, as well as nature conservation and environmental protection projects that require survey data on specific seabed conditions.

- This new standard allows buyers of hydrographic surveys to set more specific requirements to surveying companies. It gives customers the possibility to customise their requirements for the survey so that it matches their specific needs. The particularly high “exclusive order” standard is intended for areas such as harbour entrances, where it is especially important to know the exact depth measurements and where ships are sailing with very little water under the keel, explained Elizabeth Hagemann, head of department at the Danish Geodata Agency.

CO2-saving potential
The new standard also makes it possible for ships to navigate safely with less water under the keel. This allows ships to carry more cargo, resulting in fuel savings and a reduction in CO2 emissions per transported product. However, this would require areas along shipping routes with critical depths being surveyed up to the new standard.



Hydrographic surveying determines water depths by using surveying equipment such as multibeam sonars aboard a survey vessel, which makes it possible to perform highly detailed surveys of the seabed.

Hydrographic surveys are performed to collect data for a variety of purposes, such as for nautical chart production, construction projects and research.

Nautical charts indicate the water depth in accordance with an international standard adopted via the International Hydrographic Organization (IHO).

As a maritime authority, the Danish Geodata Agency is responsible for the hydrographic surveying and nautical charting of Danish and Greenlandic waters.

Private surveys in Danish and Greenlandic waters may only be performed with the permission of the Danish Geodata Agency.