Electronic Navigational Chart shown in an ECDIS on the bridge of a cargo ship. Photo
ENC: ENCs are used for paperless navigation on an ECDIS. The Norwegian Hydrographic Service produces Norwegian ENCs. Photo: The Norwegian Coastal Administration
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Electronic Navigational Charts (ENC)

Official Norwegian Electronic Navigational Charts (ENC) are issued for navigational use in an ECDIS (Electronic Chart Display and Information System).

The Norwegian Mapping Authority is responsible for producing and updating the country's official electronic navigational charts (ENCs).

ENCs are primarily aimed at professional navigators. All vessels above a stipulated size are required to navigate using official nautical charts, either in the form of approved and updated paper charts, or an approved ECDIS (Electronic Chart Display System). When used in an ECDIS system, ENCs can replace paper charts for navigation.

What is an ENC?

An ENC is a vector chart that contains all the information necessary for safe navigation. These electronic charts are produced according to the International Hydrographic Organisation (IHO) standards for the exchange of digital chart information (S57).

ENCs are used for paperless navigation in an ECDIS. The ECDIS provides the navigator with a seamless presentation of the electronic charts with real-time positioning. The ECDIS also provides a continuous display of its own and other vessels’ position and movement. The ENC shown in an ECDIS makes it possible to combine electronic navigation aids in a unique way.

In several large norwegian ports depth contours and depth areas are condensed at intervals of 1 m. Here, calls can be planned and carried out using a safety contour that can be set based on the boat's depth and not the map's standardized interval of 5-10-15-20m. The additional depth information is in the Berthing ENCs. A densification of depth information is planned in several selected ports and narrow straits.

Scale and presentation standards

ENCs are edited in given scales, just like paper charts, and must adhere to a strict set of standards for the presentation of data (symbols, colours, line thickness, size, etc.) and these vary little across national boundaries.


All navigation-critical corrections and updates are published in the Norwegian notices to mariners, Etterretninger for sjøfarende (Efs), every fourteen days – and are continually updated in the ENCs. This also applies to temporary (T) and preliminary (P) messages. All who navigate using ECDIS are obligated to sail using updated ENCs.

Electronic charts in chartplotters

Manufacturers of electronic charts for chartplotters purchase their data from the Mapping Authority, either official ENCs or digital versions of paper charts. Charts used in chartplotters are not official products and are not considered authorised charts. This is because they may not be updated regularly enough or are not produced according to given international standards.

Manufacturers of electronic charts for chartplotters often add practical information that may be useful to the recreational user, or information of a more commercial nature. Some of the information provided by the Mapping Authority may also have been removed for various reasons. This may be because the manufacturer does not consider the information as relevant for the recreational user, or because it is technically impossible to include.

Therefore, there is a difference between an official electronic chart (ENC) and electronic charts that are used in chartplotters. Although suppliers of unofficial electronic charts can update the maps in line with the official charts, they are not bound to frequent updates. The regularity with which charts for chartplotters are updated will vary between suppliers.

See an overview of suppliers offering electronic charts for chartplotters, based on chart data from the Mapping Authority and how often they update their charts.

Electronic chart systems

There are many different types and models of electronic chart systems, but they can be divided into three main groups:

Electronic Chart Display and Information System (ECDIS)

An ECDIS displays all chart information required for safe and efficient navigation, and chart data must be provided and approved by an authorised charting authority. In Norway, the Norwegian Mapping Authority (Kartverket) is the authorised charting authority.

ECDIS is a navigation information system that complies with the requirements set by the International Maritime Organisation (IMO). When used with an approved backup system, it is considered a legal replacement for paper charts  if the data is prepared in accordance with the stipulated requirement specifications (S57 ENC Product Specification). The ECDIS must also be type-certified.

Electronic Chart System (ECS)

The Electronic Chart System (ECS) is a common term for chart systems that do not comply with the "IMO Performance Standards". Such systems will not satisfy the requirements related to navigational charts on board vessels as defined in SOLAS Chapter V (International Convention for the Safety of Life at Sea).

An ECS system must therefore be considered purely as a navigational aid, and cannot be used as a legal replacement for paper charts on board vessels.

Raster Chart Display System (RCDS)

This chart system uses raster data. As a result, the system does not comply with the ECDIS requirements. The International Maritime Organisation (IMO) has therefore not approved raster charts as an alternative to paper charts, but still permits use of raster data in ECDIS if there is no relevant ENC data for the area.

However, it must be emphasised that the use of raster charts in Norwegian waters will not supersede the requirement to have updated paper charts on board.

Primar ENC Service

Primar is an international cooperation for the provision of a consistent and reliable Electronic Navigational Chart (ENC) service. It is a worldwide ENC service operated by the Norwegian Hydrographic Service on a non-profit basis.

The service incorporates the regional ENC coordinating centre (RENC), based on bilateral agreements with several nations as well as direct licence and distributor agreements with other hydrographic offices and distributors. The Primar RENC is operated in accordance with the worldwide electronic navigational chart database (WEND) principles of the International Hydrographic Organisation (IHO).

The Primar RENC also cooperates with other RENCs, such as IC-ENC in the UK. This collaboration covers standards and technical issues as well as the distribution of information to the global shipping market.

Read more about Primar.