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Miscellaneous Notices to Mariners

5 Electronic Navigational Charts (ENC)

In connection with new surveying of the Norwegian coast, the Norwegian Hydrographic Service is prioritizing the publication of electronic navigational charts authorized for navigation. The international designation of such charts is ENC (Electronic Navigational Chart).

ENCs are produced in accordance with the International Hydrographic Organization's (IHO) S-57 standard, which is applied by all hydrographic offices world-wide for the production of corresponding electronic navigational charts for their waters.

ENCs for the entire Norwegian coast are available through authorized PRIMAR distributors. Information about coverage and overview of distributors is available from

5.1 Electronic Chart Display and Information System (ECDIS)

ECDIS is a certified navigation system meeting SOLAS requirements to navigational equipment pursuant to certain criteria. If an ENC is installed on this type of system and kept updated, it may be used for navigation in the same manner as an updated paper nautical chart.

Other types of unofficial electronic charts, for example charts produced by private industry or raster charts, can only be used as a supplement for navigation.

The following back-up systems are approved for use on Norwegian vessels:

  1. Updated paper nautical charts, or
  2. ECDIS No. 2 connected to an emergency power source.

IMO requirements for mandatory use of ECDIS

In 2008, the International Maritime Organization's (IMO) Maritime Safety Committee (MSC) approved provisions regarding the mandatory use of ECDIS. The implementation phase will cover the period from 2012 to 2018, depending on the type of vessel and its size.

5.2 Official Norwegian Electronic Navigational Charts (ENC) for Norwegian Waters

Official electronic navigational charts (ENC) are vector charts produced in compliance with the specifications given by the International Hydrographic Organization, and are approved by a national hydrographic office.

5.2.1 Norwegian ENCs

The sources for Norwegian ENCs are either digitalized or scanned analog charts, or a database. The data is compiled into a seamless database in which each ENC is a cell. Each cell is identified by a unique number.

The content of charts and ENCs in the same area is not always identical. The ENC often contains more detailed data.

Depths along the quay

Quay depths are taken either on the quay or two meters away from the quay depending on when the measurements were taken. The position of quay depths maybe presented slightly away from the quay in the electronic navigational chart (ENC) in order to improve readability in ECDIS.

5.2.2 ZOC Diagram

The data sources for an ENC will for many areas be based on old hydrographic data with inferior positional accuracy compared to what is possible with modern technology. These areas are identified by the use of Zones of Confidence (ZOC).

See ZOC diagram in chapter 1.5 Zones of Confidence – ZOC-diagram

Norwegian ENCs are divided into the following user bands:

User bands
NameScale RangeAvailable Compilation
Scale Range
1 Overview <1:1 499 999 3 000 000 and smaller
1 500 000
200 NM
96 NM
2 General 1:350 000 – 1:1 499 999
700 000
350 000
48 NM
24 NM
3 Coastal 1:90 000 – 1:349 999
180 000
90 000

12 NM
6 NM

4 Approach 1:22 000 – 1:89 999
45 000
22 000
3 NM
1,5 NM
5 Harbour 1:4000 – 1:21 999
12 000
0,75 NM
0,5 NM
0,25 NM
6 Berthing > 1:4000 3999 and larger < 0,25 NM

5.2.3 Update Files (ER Updates)

An advantage with ENCs is the possibility for automatic updates. Update files (ER)
are issued every fortnight. Within a 14 day period, all notices from the last Etterretninger for Sjøfarende (Efs) will be included. The ERs may also include updates that have not been issued in the Efs.

Temporary (T) and preliminary (P) notices are distributed for the ENCs in the same way as other updates.
We welcome feedback from our users regarding how this service works. Please send comments to

All ER updates are distributed through PRIMAR. For larger updates New Editions of an ENC will be issued. A New Edition may also be issued for technical reasons.

5.2.4 Terms Used

New dataset: ENC dataset that has not been issued for navigational purposes earlier.

Update: Amendments to existing dataset.

New edition: It also includes new data that have not been released earlier, in addition to all the previous updates.

5.2.5 Warning

Use of modern equipment makes it possible to extend the use of nautical chart information beyond what it is intended for. We strongly advise against this.

It is at all times the mariners own responsibility to familiarize themselves with and use the information in a chart in a responsible manner. Do take into consideration the constraints of the information the charts provides.

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