Chart FAQs
What are IMO nautical chart carriage requirements?
The 1974 International Convention for the Safety of Life at Sea (SOLAS 1974), subsequently amended in 2000 and 2002, specifies the requirements for navigational equipment to be used onboard ships flying the flags of parties to the convention. This Convention was adopted by the International Maritime Organisation (IMO), the United Nations Organisation that is concerned with maritime transportation. IMO member states are obliged to adopt IMO rules and regulations into their national legislation.The country in which a ship is registered and, hence, which flag it is flying is known as its Flag State. It is the national maritime administration of the Flag State that controls the adherence to SOLAS carriage requirements on a ship. This is commonly known as Flag State control.
The national maritime administration of a country is also usually responsible for ensuring that ships which arrive in its ports comply with Flag State regulations and international agreements. This is commonly know as Port State control.
In addition, Port states within regions usually cooperate to apply consistent standards in their region, for example the European nations and Canada cooperate under the umbrella of the Paris Memorandum of Understanding (Paris MOU.)
In other words, the specific rules which apply to any given vessel regarding chart carriage requirements are a mixture of international, flag and port requirements and it is the responsibility of the Captain to ensure that his vessel complies with all the applicable rules for the voyage being undertaken and the ports visited.
The specific IMO requirements for carriage of nautical charts are laid down in SOLAS Chapter V, the applicable parts are:
IMO SOLAS V/2 (defines the nautical chart)
- 2.2 Nautical chart or nautical publication is a special-purpose map or book, or a specially compiled database from which such a map or book is derived, that is issued officially by or on the authority of a Government, authorized Hydrographic Office or other relevant government institution and is designed to meet the requirements of marine navigation. The nautical charts and nautical publications referred to in regulation V/2 are commonly referred to as "official" charts and publications.
- 2.1 All ships irrespective of size shall have:
- 2.1.4 nautical charts and nautical publications to plan and display the ship's route for the intended voyage and to plot and monitor positions throughout the voyage; an Electronic Chart Display and Information System (ECDIS) may be accepted as meeting the chart carriage requirements of this subparagraph.
- 2.1.5 back-up arrangements to meet the functional requirements of subparagraph 2.1.4, if this function is partly or fully fulfilled by electronic means.
- Nautical charts and nautical publications, such as sailing directions, lists of lights, notices to mariners, tide tables and all other nautical publications necessary for the intended voyage, shall be adequate and up to date.
- Most vessels still satisfy carriage requirements for charts and publications by the use of paper products, however amendments to SOLAS regulations that came into force in July 2002 allow these carriage requirements to be satisfied solely by electronic means so long as a suitable back up is provided.
- The three regulations referred to above show that the carriage requirement for charts and publications can be fulfilled by: Carriage of official and up to date paper charts, or carriage of a type-approved ECDIS (in accordance with the requirements of the IMO ECDIS Performance Standards ? i.e. using up to date Electronic Navigational Charts (ENC) supplemented by an appropriate back up arrangement).
What kinds of digital nautical charts are available?
There are two types of digital chart; raster charts and vector charts.A raster chart is simply a scanned image of a paper chart, whereas a vector chart is a digital database of objects, such as, points, lines, areas, buoys, etc., that can not only be displayed as an image on a navigation system, but also queried for additional information.
What are "official" nautical charts?
These are charts issued by or on the authority of a government authorized Hydrographic Office or other relevant government institution that may be used to fulfil carriage requirements - provided they are kept up to date by the user.As well as official paper charts, there are two kinds of official digital charts commonly available; Electronic Navigational Charts (ENCs) and Raster Navigational Charts (RNCs), of which the most well known are UKHO ARCS charts.
All other nautical charts are by definition unofficial and are often referred to as private charts. These charts are not accepted as a formal basis for navigation under the SOLAS convention.
What is an ENC?
ENC stands for Electronic Navigational Chart and was originally introduced to signify a digital chart that complied with the IHO chart data transfer standard S-57. By definition, ENCs can only be produced by or on the authority of a government, authorised Hydrographic Office, or other equivalent government institution.ENC content is based on the source data of the responsible Hydrographic Office and are always referred to the World Geodetic System 1984 Datum (WGS84). ENCs are regularly updated with information that is digitally distributed.
How do I recognise an ENC?
Firstly, ENCs can only be purchased from an authorized distributors, who will alway suppy the ENC as part of a subscription service that includes the delivery of updates throughout the subscription.Secondly, a type-approved ECDIS can distinguish an ENC from unofficial chart data. If unofficial data is shown on the ECDIS display, its boundary is identified by a special line style. This boundary is visualized as a one-sided RED line with a diagonal stroke on the unofficial side of the line:
Finally, the mariner can normally use the ECDIS or ECS system to interrogate the chart data and get details, such as, chart producer, edition number, update status, etc.
How are ENCs distributed?
The majority of ENCs are made available to end-users in a protected format called IHO S-63. S-63 is designed to maintain the integrity of all transactions between service provider and end-user and enable the end user systems to check the authenticity of the data they are sent. S-63 ENCs are usually distributed to the end-user by CD because of the large amount of data involved.In order to load and display S-63 protected ENCs, the end-user needs "Chart Permits" that are usually emailed to them by their service provider. The chart permits are loaded into the ECDIS and allow the licensed charts to be loaded from the CDs and displayed in the ECDIS. Chart permits need to be renewed whenever the ECDIS is changed, subscriptions are renewed, or additional ENCs are licensed.
A few nations (most notably the USA) distribute their data in unencrypted S-57 format, rather than encrypted S-63. All type-approved ECDIS systems are able to load and display S-57 ENCs without chart permits.
Can ENCs be distributed in formats other than S-57 and S-63?
Yes. Subject to specific approval of the format concerned and its distribution system, and subject to approval by the producing hydrographic office, the International Hydrographic Organisation has approved the direct distribution of ENCs in the internal, machine code format used by the individual ECDIS manufacturer.The generic name for this type of distribution is "SENC Distribution" and, depending on the make of ECDIS involved, this can make it significantly easier and faster to load ENCs into an ECDIS.
ChartWorld is approved to distribute many ENCs in the SevenCs SENC format called "DirectENC."
What is an RNC?
An RNC is a "Raster Navigational Chart." RNCs are digital raster copies (i.e. digital images) of official paper charts conforming to IHO Product Specifications RNC S-61.RNCs can only be issued by, or on the authority of, a national Hydrographic Office. RNCs are regularly updated with official update information distributed digitally.
Because of their nature, RNCs do not provide the same level of functionality that are provided by ENCs and many flag states do not recognise RNCs as meeting SOLAS chart carriage compliance requirements.
How are RNCs distributed?
The main RNC service operated by ChartWorld is the UKHO ARCS service.ARCs is physically distributed to vessels on 11 area CDs and the chart permits are usually distributed separately by email. The chart permits are imported into the ECDIS (or ECS) and then the charts can be installed.
Chart updates are, in the form of update CDs, are issued regularly.
One of the advantages of ARCS is that all charts are usually aboard and can be activated simply by requesting a chart permit that can be delivered by email.
How are ENCs and RNCs kept up-to-date?
In order to meet carriage requirements, official paper charts must be regularly corrected by the user using HO issued Notices to Mariners.Similarly, ENCs and RNCs are kept up-to-date by applying regular updates that are usually provided by the data providers on a weekly basis. The update file may be transferred by wireless transmission or, more normally because of the volume of data involved, by CD, which are then loaded into the ECDIS to be updated.
Remote updating using satellite or (when in port) shore based communications is becoming more common as the availability of high bandwidth ship to shore communication increases.
Is it possible to check that all updates have been applied to an ENC?
Yes. Updates to ENCs are sequential, and the sequence is unique to each ENC. Therefore, during the updating process a type-approved ECDIS always checks that all updates in the sequence have been applied and alerts the user if an update is missing and prevents further updates to the ENC concerned until the missing update is applied.A type-approved ECDIS maintains a list of updates applied and the date of application. This list can be used to check the update status of the ENCs loaded. Should all available ENCs show the same date for the latest update, it is likely that they have not been updated regularly, and the chart distributor should be contacted for verification. Port State Control officers may use the ECDIS listing to ensure that ENCs are being kept up to date in accordance with SOLAS V Regulation 27.