ECDIS - Electronic Chart Display and Information System

ECDIS is much more than simply images of a chart on a computer screen. It is a combination of type-approved hardware and software, using authorised data, that provides a powerful decision making tool on the bridge of a ship by combining satellite and other position fixing with ship's sensors and a sophisticated electronic database containing charting and other navigation information.

A typical ECDIS installation in a ship

The chart information in ECDIS is continuously analysed and compared with a ship's position, intended course and its manoeuvring characteristics to give warning of approaching dangers. ECDIS also provides alerts and prompts for planned course alterations. Additional material, such as photographs and views, as well as navigational notices and cautions can be accessed instantly and displayed as required on high resolution full colour screens. In addition, ECDIS provides many other sophisticated navigation and safety features, including continuous data recording for later analysis.

In the future, ECDIS will also incorporate and display information contained in other nautical publications such as Tide Tables and Sailing Directions and incorporate additional maritime information such as radar information, weather, ice conditions and automatic vessel identification.
The chart database used in ECDIS is known as an Electronic Navigational Chart (ENC). ENCs and their updates are only published by or under the authority of governments. As such, they carry full official status and the backing of the issuing government.

The chart information in an ENC is not held as a single image or "picture" of a chart, but as individual items (vectors) in a database. Each chart feature and its associated information is recorded separately in the database. This allows all the chart data to be analysed and re-assessed continuously by ECDIS in relation to a ship's current and intended position. Dangers or hazards which will affect a ship can then be identified automatically and warnings and alarms raised.

ECDIS supports a comprehensive update mechanism to ensure ENCs can be kept up to date, with things such as Notices to Mariners. Chart maintenance is achieved in effect automatically via disk update, e-mail message or satellite data transfer.

The versatility of the ENC vector chart database and the comprehensive ECDIS display and performance standards allow the mariner to select and display navigational information most relevant to the requirements and the situation at the time. For example, ECDIS will display and respond to the safety depth contour based on a vessel's actual draft. The level of chart detail that is shown can also be adjusted according to the circumstances and alternative colour schemes can be selected for use by day or by night.

ECDIS and ENCs must conform to rigorous standards regarding how they operate and what information is displayed. The standards govern such things as chart data structure, minimum display requirements and minimum equipment specifications as well as many other aspects. The International Hydrographic Organization (IHO) and the International Maritime Organization(IMO) set the ECDIS and ENC standards.

Legal Status of ECDIS in Australia

When used in an IMO compliant ECDIS systems, Official ENCs (and Official RNCs for those areas not yet covered by ENCs) will allow vessels navigating in Australia to meet the strict electronic chart carriage requirements of SOLAS Chapter V.

ECDIS "Dual fuelling" and "RCDS"

The so-called "dual-fuelling" concept of operation for ECDIS equipment was accepted by the IMO Safety of Navigation Sub Committee at its forty fourth meeting (NAV44) in London in July 1998 and subsequently approved by the IMO Maritime Safety Committee in the following November. This means that ECDIS equipment can be operated under SOLAS using both raster and vector charts provided that the charts are official – meaning that the chart data is only supplied by, or under the authority of a government, such as Seafarer RNCs and Australian ENCs supplied by the Australian Hydrographic Service.

When the ECDIS is viewing RNCs in areas where no ENCs are available it said to be operating in Raster Chart Display System (RDCS) mode.

RNCs are scanned images of official paper charts and like ENCs are only published under the authority of governments and their hydrographic offices. RNCs can provide some, but not all of the functions of ENCs.

The Navigation Sub-Committee was told that Hydrographic Offices are fully committed to seeing the widespread use of ECDIS and are busy producing ENCs, but it is generally acknowledged that it will be several years before sufficient numbers of ENCs are available to provide continuous coverage for world voyages. This is because there is so much more information in an ENC than in a paper chart and so they take more time to produce.

However, official raster charts already cover much of the world and the idea of ECDIS operating in RCDS mode is seen as a way of letting ship owners and navigators maximise use of ECDIS equipment prior to full ENC coverage.

The Australian Hydrographic Service released its Raster Navigational Chart product - Seafarer RNC – in 1997.  Full Seafarer RNC coverage is available of the Australian Charting Area.  Australian ENCs have been progressively released through the IC-ENC distribution network since 2004 and the Australian Hydrographic Service is committed to providing full ENC coverage of its Charting Area during 2010. 

Seafarer RNCs

Seafarer RNCs are scanned images of the official Australian paper charts and are published by the Australian Hydrographic Service on CD-ROM. They contain exactly the same information as official paper charts and maintain the same standards of quality, reliability and government backing. Like ENCs and paper charts, they are supported by a Notice to Mariners update service monthly on CD. Seafarer RNC uses Hydrographic Chart Raster Format (HCRF), which is the same format and standard used by the British Admiralty.

When ECDIS is operated using an Electronic Navigational Chart (ENC), an official vector chart, the system does not require paper chart support. However, when ECDIS equipment is operated in the secondary Raster Chart Display System (or RCDS) mode (using official raster charts) the IMO have determined that "an appropriate folio" of up-to-date paper charts must be carried in order for a vessel to comply with the regulations. The IMO also determined that RCDS mode was only valid for those areas where ENC have yet to be created. In this way, the "dual-fuelling" concept includes a clear policy of ENCs replacing raster charts as soon as they become available.

It is up to national Maritime Authorities to determine what constitutes "an appropriate folio of paper charts". It is generally understood that such a folio should result in a significant reduction in the number of paper charts that must be carried.
The Australian Maritime Safety Authority (AMSA) has issued a Marine Notice covering their requirements for ships using ECDIS to meet the chart carriage requirements of SOLAS Chapter V. There is a set of explanatory notes that accompanies the Marine Notice.

Australia’s RNCs are available through Seafarer Product Distributors. Annual subscriptions to chart updates can also be purchased and are supplied monthly, on a CD-ROM. This allows Notices to Mariners updates to be applied to RNCs virtually automatically.

Australian ENCs are commercially available through the international IC-ENC distribution network - See Press Release. An annual subscription to chart updates is included in the purchase price.

However, Australian port authorities and Australian pilot companies may request Australian ENCs that cover their port limits or areas of operation, directly from the Australian Hydrographic Service.  Beyond these limits, it is considered that the IC-ENC distribution network should be used.  For further information please contact the AHS Licensing Manager.

ECS - Electronic Chart Systems

All electronic chart systems other than ECDIS are known simply as ECSs (Electronic Chart Systems). ECSs provide automatic plotting of a vessel's position on an electronic chart of some sort. Some ECSs provide many of the functions found in ECDIS such as route planning, route monitoring and the raising of alarms and warnings. ECSs are particularly popular with professional fishermen, small charter vessels and recreational boaters. "Chart Plotters" are ECS's. Two typical ECSs are shown below and to the right.

The charts used in ECSs come in a variety of forms. Some ECSs use RNCs while others rely on commercially produced charts ranging from very simple line drawing to images that closely resemble paper charts or ENCs. Commercial charts have no government backing or endorsement. ECS screen displays vary also. Some are small and single colour, others run through a standard PC or laptop and can provide full colour and more detail.

Legal Status of ECS

There are no agreed standards for ECSs or the versions of the charts that they use. Because of this, ECSs are NOT recognised as an alternative to paper charts where charts are required to be carried under Australian or International Regulations.

Glossary of Terms

IHO - International Hydrographic Organization, the organisation which coordinates world hydrographic charting policy and standards.

IMO - International Maritime Organization, the United Nations organisation which coordinates safety policy and standards for world shipping.

SOLAS - Safety of Life at Sea Convention - the principal international convention regulating ship safety. Administered by IMO.

ECDIS - Electronic Chart Display and Information System - highly sophisticated navigation systems designed for ships. Must conform to strict international standards.

ENC - Electronic Navigational Chart - vector chart data base published by a national hydrographic office for use in ECDIS. Must meet international standards set by the IHO and IMO.

ENC data is arranged according to S57 format and specifications.

S57 - The IHO data format and specification which governs the content, creation and display of ENCs.

S63 - The IHO ENC data protection scheme.

RCDS - Raster Chart Display System - a mode of operation for ECDIS which uses official raster charts (known as RNCs) in areas where ENCs have yet to be produced by Hydrographic Offices.

ECS - Electronic Chart Systems - non-ECDIS chart navigational systems, some of which come close to ECDIS performance.

RNC - Raster Navigational Chart - an electronic facsimile of an official paper chart for use in ECDIS RCDS mode and for RNC capable ECSs. The Australian Hydrographic Service publishes its RNCs under the name of Seafarer RNC.