Today's mariner is looking for something with the same standards of quality as the traditional paper chart, but which fits the demands of a new navigational era.

Electronic navigation, although still relatively new and unfamiliar, is becoming increasingly more commonplace, particularly onboard commercial vessels. This guide aims to provide answers to some of the most commonly asked questions regarding electronic charts.

WHAT ARE ELECTRONIC CHARTS?
Electronic charts are the next generation of navigational charts. Their electronic formats simplify traditional navigation processes such as route planning and chart updating, and also enable automation of route tracking through use of satellite positioning devices. These features can greatly enhance navigational safety by improving situational awareness, especially in busy or confined waters.

Digital technology is used to develop electronic charts from traditional paper charts and directly from marine survey data. The importance of using official data is, as with paper charts, absolutely paramount to maximising safety and other related benefits. Official electronic charts currently take two forms: Electronic Navigational Charts (ENCs) and Raster Navigational Charts (RNCs).

ELECTRONIC NAVIGATIONAL CHARTS - ENCs
ENCs are official vector format electronic charts.

ENCs consist of digitised data that records all the relevant chart features such as coastlines, buoys, lights, etc. These features and their attributes (such as position, colour, shape) are held in a database-like structure that allows them to be selectively displayed and queried, creating the potential to manipulate the chart image when displayed on screen. Because of their vector format, ENCs can also be linked to other onboard systems to provide additional automatic features such as warning alarms.

3 variations of the same ENC, showing minimum, intermediate and maximum data display levels.

ENCs, by their very nature, are fully compliant with the International Hydrographic Organisation's (IHO's) S57 Version 3 Product Standard, and can only be issued by, or on the authority of, a government-authorised Hydrographic Office (HO). Each IHO member nation is responsible for producing ENCs of its own waters, and systematically updating them with all safety-critical information.

ENC Production Status
Worldwide ENC availability has accelerated considerably in the last few years, and some areas (e.g. Northern Europe) are now populated with near seamless coverage. However, some nations do not yet have the capability and/or capacity to produce ENCs of their national waters, and so some areas will remain unpopulated for the foreseeable future.

It is safe to say that ENCs of most high priority areas (e.g. trade hotspots and key ports) will become available in the next few years, but other areas of lower priority could take far longer.

ENC Availability
Thomas Gunn Navigation Services Ltd is dedicated to providing a complete catalogue of available ENC's which are sourced from various Hydrographic offices around the World. We are committed to providing a single ‘one-stop-shop’ source for all commercially available ENC data.  Coverage Includes the UK, Gibralta, Malta, Egypt (including Suez), the Falkland Islands, and parts of the Caribbean, West Africa and the Middle East.

For further information, including details of available coverage, click here

An electronic catalogue showing commercially available, produced but not yet commercially available and planned international ENC coverage is available from the IC-ENC website.

ENC Distribution
In order to ensure uniformity in both format and distribution, the IHO created the WEND (Worldwide Electronic Navigational Database) principle. Under the WEND principle, each major geographical area of the world would have its own Regional ENC Co-ordinating Centre (RENC). Each ENC-producing nation would send its data to the local RENC, who would then be responsible for validating and distributing its ENCs to end-users.

There are currently two RENCs worldwide; Primar-Stavanger based in Norway and the International Centre for ENCs (IC-ENC) based in the UK. We can provide ENCs from both RENCs (and from other non-RENC member nations).

RASTER NAVIGATIONAL CHARTS - RNCs
RNCs use raster data to reproduce paper charts in an electronic format. Their familiar ‘paper chart’ image helps users gain confidence with the use of electronic charts, by providing a direct link between display screen and chart table.

RNCs (and in deed all raster representations) consist of thousands of tiny coloured dots (pixels), that together make a flat digital image. Every pixel is geographically referenced, enabling accurate real-time (continually updated) display of vessel position when your chart display system is linked to GPS.

Additional user defined information such as route plans and shoal areas can be overlaid on an RNC to provide automatic links to other onboard systems (e.g. warning alarms) but unlike ENCs, charted features cannot be selectively displayed or queried.

RNC samples taken from ARCS charts BA2036 and BA2675.

RNCs must comply with the IHO's S61 data standard, and can only be issued by, or on the authority of, a government-authorised Hydrographic Office (HO).

RNC Distribution
The UKHO produce ARCS, the world’s leading RNC service. Over 3,000 ARCS charts are available, providing worldwide coverage in RNC format of the globally respected Admiralty chart series.

ARCS charts carry the same guarantee of quality and accuracy as the Admiralty paper chart, and are available from Admiralty Distributors worldwide.

HOW DO I USE ELECTRONIC CHARTS?
To display an electronic chart you need either an Electronic Chart System (ECS), or an Electronic Chart Display Information System (ECDIS).

ECS is a generic description that can be used for anything from a laptop with simple navigational software to a fully Integrated Bridge System (IBS). An ECDIS is an official, type-approved display system (more than an ECS) that meets stringent IHO defined criteria.

It is important to note that when used to display non-SOLAS-compliant electronic charts, an ECDIS is classified as an ECS and can only be used as an aid to navigation (Click here for Rules and Regulations).

WHICH TYPE OF ELECTRONIC CHART IS BEST FOR ME?
Both ENCs and RNCs are official electronic charts produced from approved hydrographic office data of the highest quality. Both can be updated automatically on a weekly basis, thus reducing the amount of time the mariner has to spend manually correcting charts.

ENCs offer the prospect of paper chart equivalency and more functionality than RNCs, but although ENC coverage is steadily increasing, it will take several years to reach global levels. Due to the relative infancy of both ENC and ECDIS, regulations for their use can vary from country to country and can be confusing.

RNC services such as ARCS already offer worldwide coverage, providing navigators with the safety and operational benefits of official electronic charts virtually everywhere in the world. However, despite the fact that RNCs provide exactly the same data as their equivalent paper charts, current regulations do not support the use of RNCs for primary navigation when used independently of ENCs, and without some form of paper chart backup.

So What Does this Mean in Practical Terms?
If you wish to navigate using electronic charts as your primary means of navigation you need a type approved ECDIS with back-up, ENCs where available and RNCs such as ARCS charts to fill the gaps. Initially, the ARCS component of this 'dual-fuel' combination is likely to form the majority of coverage, so a reasonable paper chart backup will still be required (but this will gradually change as more ENCs become available).

ENC and RNC being used in combination.

 

> Is the only service available that provides global coverage of official electronic charts.

> Is user friendly as it provides an exact correlation between the familiar electronic chart on your ECS/ECDIS screen and the Admiralty paper chart on your chart table.

> Is tried, tested and more importantly trusted.

The above benefits have made ARCS the preferred choice amongst many mariners worldwide.
 

The Future of Primary Navigation
The UKHO is currently conducting sea trials of a new service, designed specifically to provide a ‘one-stop-shop’ for both ENCs and RNCs. The new Admiralty ECDIS Service will bring together ENC services from multiple sources including RENCs and other Hydrographic Offices, and will combine them with worldwide coverage of ARCS to provide a single, integrated service that will facilitate full, regulatory compliant use of ECDIS.

Shipping companies subscribing to the Admiralty ECDIS Service will purchase electronic chart coverage for specific routes or areas of operation. The UKHO will provide ENCs where available and ARCS charts where not, and will automatically issue new ENCs (at no extra cost) as coverage increases.

For the customer, this combined service means no multiple licenses, no multiple CDs, no duplicated costs and no ‘blank cheque’ scenario as additional ENCs become available within their subscription period. For further information regarding the Admiralty ECDIS Service, click here.
 

Glossary of Terms