Introduction to ENCs

Electronic Navigational Charts are vector charts that conform to IHO S57 specifications. They are compiled from a database of individual items of digitized chart data which can be displayed as seamless chart. ENC’s are far superior to Paper or Raster Charts, and are intelligent vector database that can be queried for information for displaying selected feature, object or layer containing the navigational information. The systems using them can be programmed to give warning of impending danger in relation to charted information, and the vessel’s position and movement.

The official definition of ENC is that it is a database, standardized as to content, structure and format, issued for use on an ECDIS, on the authority of government –authorized hydrographic offices. The ENC contains all chart information necessary for safe navigation, and may in fact contain supplementary information in addition to that contained in the paper chart (for example sailing directions) which may be considered necessary for safe navigation. Any other vector data is unofficial and does not meet chart carriage requirements.

All ENC’s are based on the World Geodetic System 84 (WGS84), and are organized in so called Cells.

Admiralty Vector Chart Service (AVCS)

The Admiralty Vector Chart Service (AVCS) provides comprehensive, official worldwide ENC coverage. By combining its own produced ENCs with others from the world’s national hydrographic offices, the UKHO has created a single SOLAS-compliant source of ENC coverage for use in ECDIS (Electronic Chart Display and Information Systems), that is comprehensive, official and global.

AVCS is helping the maritime community overcome historic barriers to the adoption of ECDIS, by offering the mariner usable and effective digital navigation, delivering significant gains in terms of efficiency, economy and, above all, safety.

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    AVCS is Better than Official Alternatives

    AVCS offers the most extensive ENC coverage available from any one supplier. It includes ENCs which are not available through any other services. This coverage is key for any shipping company with vessels trading internationally and is not available from any other ENC provider.

    These folios are available in three defined types (Transit, Regional and Port), and they provide customers with the best possible combination of flexibility of coverage, budgetary, predictability, and ultimately peace of mind. Such folio services are not available from any other ENC provider.

    AVCS also provides very flexible licensing to minimize chart costs. AVCS customers need only buy the ENCs they need when they need them. Chart access is provided for periods of as little as 3 months up to 1 year according to the geographic area and vessels operating requirements and priced accordingly. The vessel carries all the ENCs onboard.

    Chart permits can be requested at any time via an Admiralty chart agent and supplied on board in minutes.

    AVCS provides cost-effective coverage of the world’s major shipping routes, avoiding the need to purchase unnecessary data. AVCS is sold in two different formats, Folios & Units, offering the ultimate in purchase flexibility.


    AVCS is sold in a series of Folios, which are geographic collections of ENCs selected for a specific purpose (e.g. transiting an area). They are designed to make ordering, maintenance and licensing as easy and flexible as possible. Each Folio is automatically maintained for any relevant changes to ENC coverage.


    These are designed to provide all the coverage needed for a vessel to pass safely through a region when not engaging in local trade, saving you the expense of purchasing detailed coverage for regions that you are just passing through, whilst including more coverage to negotiate the choke points such as the Suez Canal and Malacca Straits.


    These cover a much smaller geographical area than Transit Folios and include all Coastal and some Approach ENCs, where coastal coverage is not available. Regional Folios are designed for local and coastal trade, where more detailed coverage of complex coastal waters is required. They do not include Port Approaches or Entry.


    These typically comprise Approach, Harbor and Berthing cells grouped together into a single sales unit. Under typical operational conditions, vessels approaching a port directly from an ocean passage will require only Transit and Port Folios if not engaging in coastal operation

    Where a number of major ports are grouped in a complex waterway (e.g. Japan’s “Bungo Suido and Western Inland Sea”), a single Port Folio may provide coverage for all the ports in the area.


    Hand-pick individual ENC chart coverage that meets the specific requirements of your Fleet to ensure precise coverage of your shipping routes.

    All ENCs in AVCS can be selected on a chart-by-chart basis as ENC Units. These Units are the smallest unit of sale allowed by ENC producers and usually contain ENC data approximately equivalent to a paper chart.


    Combine AVCS Folios of your choice with individual ENC charts for unrivalled coverage and voyage flexibility.

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    Benefits Of AVCS

    • The very best global ENC coverage available
    • More than 9500 ENCs and more than 180 ENCs more than the closest competitor
    • 1795 ports and the routes between them fully charted to provide berth to berth navigation using ENCs on the majority of major shipping routes
    • If you choose Admiralty you won’t need to switch to unofficial data mid voyage
    • All Charts onboard, only pay to use the charts if and when the vessel needs them
    • Flexible licensing for as little as 3 months up to 12 months to minimize chart cost
    • All charts updated every week for all changes online or via CD to provide the same accuracy and assurance as all other Admiralty products and services


The Admiralty ECDIS Service is the first global system of navigation combining official vector charts with official raster charts that is safe, accurate and easy to manage from UKHO with their unrivalled reputation for quality and excellence.

Electronic Navigational Charts used in the ECDIS system are the most advanced nautical charts available in vector format using data from IC ENC and Primar; they are issued only on the authority of a national hydrographic office, and provide the most comprehensive and current chart information available.

The other component, Admiralty Raster Charts or ARCS are high quality, digital versions of the world renowned British Admiralty series of paper charts. They are widely used by the commercial shipping industry and comply with the exacting Raster Navigational Chart (RNC) performance standards set by the IMO which mandates that ARCS can be used with Flag State approval, for primary navigation where ENC’s are not yet available. Moreover ARCS is also a preferred chart for planning purposes.

The UKHO compares both coverage and scale of ARCS charts with all newly released ENCs and automatically replaces ARCS with new ENCs as their coverage increases, eliminating the apprehension of unpredictable pricing or the burden of heavy administration associated with use of ENCs.

The ENCs used in the Admiralty ECDIS Service meet SOLAS carriage requirements when kept up to date and used within an ECDIS with suitable back up. They are 100% official.

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    Regulations governing the use of ENCs and ECDIS

    IMO SOLAS Chapter V, Regulation 19, 2.1.5 All ships irrespective of size shall have 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 sub paragraph. IMO resolution MSC.86(70) permits ECDIS equipment to operate in a Raster Chart Display System (RCDS) mode in the absence of Electronic Navigational Charts (ENC). However when operating in the RCDS mode, ECDIS should be used together with an appropriate folio of up-to-date paper charts. IHO Product Specification for RNC, Foreword.
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    The Benefits of UKHO ECDIS Service:

    • Seamless worldwide coverage over 38 geographical areas.
    • The first global service to provide a compliant combination of ENCs and ARCS as a single package so shipping companies can take full advantage of a superior advanced product like ENC while the coverage is still growing.
    • 100% official data providing the most accurate and safest chart information available.
    • Fixed Annual Cost – contributes to financial stability. No cost duplication.
    • New ENCs automatically supplied as they become available and at no extra cost to keep your customers SOLAS compliant at no additional cost.
    • All ENCs and ARCS charts continuously updated via the Admiralty weekly update service through the Update Cds. Updates include all Notices to Mariners, New Editions, Replacement Charts and Temporary and Preliminary Notices for all charts ensuring maximum safety.
    • Peace of Mind: Unrivalled chart accuracy allows you to navigate safely and with confidence.
    • Flexibility: Every Admiralty ECDIS Service customer is provided with a complete set of Base disks containing every ENC and ARCS chart available within the service. Access is provided by special folio ‘unlock’ (permit) keys, allowing you to carry global coverage whilst only paying for the level of folio coverage you require. Significantly, this allows the flexibility to upgrade coverage during a licence period.
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    Global Electronic Chart Coverage in the Admiralty ECDIS Service

    ENC coverage is continuously growing and we will continue to keep you updated as coverage improves. Please note that ARCS coverage is now available in all areas other than Japanese, Ecuadorian and larger scales in Malaysian waters.