Unfortunately, there is quite a list of terminology that goes with this topic. We have explained some of the terms used in this document.

A more comprehensive explanation of the issue and terminology can be found on our web site, including links to other relevant documents and web sites. This information can be found here.

On the common paper chart type system, charts are supplied by a recognized hydrographic office and supplemented by weekly Notices To Mariners which the officers onboard the vessel will update by way of chart corrections.

ECDIS on the other hand, is considered the primary system for a paperless chart system, interfaced with GPS and DGPS, and provides real time information. ECDIS comprises of ECDIS software and hardware and Electronic Navigational Charts (ENCs).


IMO performance standards are contained in Resolution A.817 (19) and state that ECDIS will be accepted as complying with V/20 of SOLAS 1974, and should be supplied with adequate backup arrangements. Importantly, this resolution also states that the chart information to be used in ECDIS should be the latest edition of the information originated by a government authorized hydrographic office and conform to the International Hydrographic Office (IHO) standards. The transfer standard for digital hydrographic data should also follow the IHO S-57 format. Furthermore, the specification for chart content and display aspects should be in the IHO S-52 format. Therefore, it should be clearly noted that ECDIS only fulfils compliance with SOLAS V/20(4) after merging the ENC contents and updates into SENC (System Electronic Navigation Chart). The SENC format is often different between different manufacturers.


We bring to members' attention that we understand that the International Hydrographic Office (IHO) has been contemplating allowing the delivery of official ENC DATA in the SENC format instead of requiring that the cells be delivered to the ship in the S-57 format (encrypted or not) and to have the conversion completed on board by the system. As a result, a proposal being discussed is that the Hydrographic Offices will deliver their chart cells to Regional Electronic Navigation Centre (RENC) and may allow them to deliver the data encrypted according the VAR’s SENC format (VAR - Value Added Retailers). This may allow for inclusion of new features, but the danger is that in case of business interruption of the VAR (for whatever reason), or the inability or unwillingness to provide certain ENCs for certain regions, no one else would be able to provide the necessary information because the SENC is proprietary. It is therefore essential that the rules requiring delivery in S-57 format be maintained. This is the only way to ensure that one will be able to buy ENCs from a variety of suppliers and maintain free enterprise.


The coverage in S-57 format provided by Hydrographic Offices is limited. In spite of recent improvements, coverage is in need of further development.

Increased availability of electronic chart data in the ENC S-57 format supported by nationally recognised Hydrographic Offices is a necessity because some data providers are actively promoting their own data product in direct competition with official HOs.


Accordingly, the profusion of different formats makes it difficult for system manufacturers to adapt. Most system manufacturers are reluctant to adapt their ECDIS to read a wide range of formats because of costs involved in gaining type approval.


Therefore INTERTANKO recommends that the IHO seeks to adopt a common S-57 encryption standard which will be freely available to all RENCs and their authorized distributors and individual HOs. INTERTANKO further recommends that as part of their type approval process, all ECDIS manufacturers and data providers should agree that at the ship owner’s request, they will freely make S-57 to SENC conversion possible.


Contact:Howard Snaith on e-mail: howard.snaith@intertanko.com