Introduction to Electronic Chart Systems and ECDIS


The electronic chart is a relatively new technology that provides significant benefits in terms of navigation safety and improved operational efficiency. More than simply a computer display, an electronic chart is a real-time navigation system that integrates a variety of information that is displayed and interpreted by the Mariner. It is an automated decision aid capable of continuously determining a vessel's position in relation to land, charted objects, aids-to-navigation, and unseen hazards. The electronic chart represents an entirely new approach to maritime navigation.

There are two basic types of electronic charts. Those that comply with the International Maritime Organization (IMO) requirements for vessels, known as the Electronic Chart Display and Information System (ECDIS), and all other types of electronic charts, regarded generically as, Electronic Chart Systems (ECS).

Requirement for ECDIS

For an ECDIS to meet a minimum level of reliability and functionality, the IMO has developed a performance standard for ECDIS. This standard specifies how an ECDIS must work in order that it serves as an adequate alternative to the paper nautical chart. The IMO Performance Standards permit National Maritime Safety Administrations to consider ECDIS as the functional equivalent to nautical charts required by Regulation V, Chapter 19 of the 1974 Convention on the Safety of Life at Sea (SOLAS V/19) (as amended). IMO has specifically requested that member governments encourage their National Hydrographic Offices to produce electronic navigational charts (ENCs) and provide the associated updating service as soon as possible, and to ensure that manufacturers conform to the performance standards when designing and producing ECDIS. (See the Industry Links containing known organizations providing services and products associated with ECDIS).

Electronic Charts - What Can Be Used Under SOLAS?

The last few years have seen a steady increase in the use at sea of electronic chart systems and the associated electronic chart data. Unfortunately, this increased use appears to have been accompanied by some confusion regarding the "electronic chart" solution and what is, and what is not, legitimate for vessels subject to the requirements of SOLAS V/19. The CHRIS Committee at its15th meeting (Monaco, 10-13 June 2003) produced an information paper to explain the various contributing elements of the "electronic chart" solution, their inter-relationship,and their status under SOLAS V.

The full text of this paper is available in English Français Español

Who Produces and Who Sells ENCs?
ENCs are produced and authorised by national hydrographic authorities such as Hydrographic Offices. ENCs are eventually sold by chart agents and other suppliers in a similar way to paper charts.

What is a RENC?

To assist the global distribution and availability of ENCs, the IHO has encouraged the establishment of Regional ENC Coordination Centres (RENCs). Each RENC is a not-for-profit organization that is controlled by the Member States who distribute their ENCs through that RENC. RENCs ensure that all the ENCs that they handle are consistent. The RENCs also make ENCs available to retailers from a single wholesale source. RENCs are part of the official supply chain for ENCs.

Further information about RENCs and the services that they provide is available from their respective web sites:

PRIMAR - (Home Page)

IC-ENC - (Home Page)



Associated IHO Standards
In conjunction with the development of IMO Performance Standards for ECDIS, the International Hydrographic Organization has developed technical standards related to the digital data format, specifications for ECDIS content and display, and data protection.

 

  • IHO Special Publication 52 (S-52) includes appendices describing the means/process for updating, colour and symbol specifications, and a glossary of ECDIS-related terms.
  • IHO Special Publication 57 (S-57) includes a description of the data format, product specification for the production of ENC data, and an updating profile.
  • IHO Special Publication 63 (S-63) includes a description of the IHO recommended ENC security scheme with two appendices relating to associated security test data sets and to the use of earge media support.

    IHO S-57, S-52 and S-63 are specified in the IMO Performance Standards for ECDIS.

Testing ECDIS and Type Approval Requirements
The International Electrotechnical Commission (IEC) has identified and described the necessary performance tests and checks for an IMO-compliant ECDIS. IEC Publication 61174 is the basis for type-approval specifications related to operational methods of testing and required test results for an IMO-compliant ECDIS. IEC 61174 is used as the basis for type-approval/recognition by Maritime Safety Administrations for an IMO-compliant ECDIS.

Electronic Chart Data

  • Electronic Navigational Charts (ENC). ENCs are vector charts that conform to IHO specifications, as contained in Publication S-57. They are compiled from a database of individual items ('objects') of digitised chart data which can be displayed as a seamless chart. When used in an ECDIS or some ECS, the data can be reassembled to display either an entire chart image or a user-selected combination of chart data. ENCs are "intelligent" in that systems using them can be programmed to give warning of impending danger in relation to charted information and the vessel's position and movement.
  • Raster Nautical Charts(RNC). RNCs are raster charts that conform to IHO specifications and are produced by digitally scanning and geo-referencing the image of a paper chart. In other words, every pixel that makes up the image is associated with the geographical position that it represents. The image may be either the finished chart itself or the stable colour bases used in the multi-colour printing process. The resulting digital file may then be displayed in an electronic navigation system where the vessel's position, generally derived from electronic position fixing systems, can be shown. Since the displayed chart data are merely a digital photocopy of the original paper chart, the image has no direct "intelligence" and the chart data cannot be interrogated or analysed to trigger alarms or warnings. However, because the image is georeferenced, a mariner can still indicate positions on the chart at which a warning will be activated. IHO Special Publication S-61 "Raster Nautical Chart Product Specification" provides guidelines for the production of raster data. IMO resolution MSC.86(70) permits ECDIS equipment to operate in a Raster Chart Display System (RCDS) mode in those areas where Electronic Navigational Charts are no yet available. The RCDS mode of operation is described in Appendix 7 of the IMO Performance Standards for ECDIS.

SENC Delivery
At the 16th International Hydrographic Conference, (Monaco 14 -19 April 2002), the IHO Member States agreed a "SENC Delivery Option" (decision 17.e of the conference refers) for ECDIS, thus allowing that ENC data could be distributed in proprietary SENC formats as well as in the fundamental IHO S-57 format. This resulted in an amended paragraph 3.3 of S-52 and a new IHO Technical Resolution A3.11

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