Admiralty Quick Guide to ENC Symbols - Reference Guide

Nov 1, 2026

Quick reference guide focused on recognizing lesser-known ENC (Electronic Nautical Chart) symbols used in daytime colours on ECDIS displays. Explains key symbols and their meanings, including generic isolated danger, low-accuracy sounding, caution areas, dredged areas, charted data at smaller scale, boundaries between IALA buoyage systems, query symbols, and virtual aids to navigation. Notes how night-time palettes may change colours and points readers to ECDIS Chart 1 and cursor enquiry for additional information.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages2

Reading Time5 min

AccessFree to download

Quick Guide to ENC Symbols

Symbol meanings and references

Cursor enquiry and additional information

Symbol settings on ECDIS

Quick Guide to ENC Symbols This quick reference guide is to help you recognise some of the lesser known ENC symbols. It is not intended to replace ‘ECDIS Chart 1’. The ENC symbols shown are in daytime colours. They may be shown in different colours/shades in night-time palette. | ENC Symbol | | Explanation | | | Additional Information | 5011 Ref | | --- | --- | --- | --- | --- | --- | --- | | | | Generic isolated danger symbol – with less depth than user-selected safety contour or where the depth is unknown | | | Wreck, rock or obstruction | K | | | | Sounding of low accuracy | | | Equates to sounding of doubtful depth in 5011 | I2 | | | | 6 stars
5 stars
4 stars
3 stars
2 stars U | A1
A2 B
CD | All significant seafloor features detected; very high accuracy survey
All significant seafloor features detected; high accuracy survey Uncharted features dangerous to navigation are not expected but may exist; medium accuracy survey
Depth anomalies may be expected; low accuracy survey or passage soundings Large depth anomalies may be expected; poor quality data
Quality of bathymetry yet to be assessed | | | | | | Caution area where a specific caution note applies | | | Refer to cursor enquiry for more information.
Refer to ECDIS Chart 1 for more examples | N64 | | | | Dredged area deeper than safety contour Darker blue indicates water shoaler than safety contour | | | Refer to cursor enquiry for more information | | | | | Vertical lines indicate areas of charted data at significantly smaller scale than main display | | | Zoom out until vertical lines disappear to view at scale appropriate to data | | | ~~ A B A B ~~ | | Indicates boundary between IALA A and Bbuoyage systems | | | See NP735 | | | ?
? ? ? ? ? | | Isolated query indicates insufficient information to symbolise the feature. Query associated with symbol indicates absence of a mandatory attribute, such as beacon shape, direction or orientation. | | | Query may appear alone at a point, on a line or in a defined area. Further information may be obtained from cursor enquiry of the query | Q80 | | | | Virtual aid to navigation with no physical structure | | | ECDIS / ENC based symbol | | |
| | Limit between area of unofficial vector data and official ENC data, marked by orange pecked line – pecks angled towards unofficial vector data | | | May be shown the other way around on older ECDIS. Within areas of non-ENC data, an alternative, official chart must be used for navigation | | | ENC Symbol | | Explanation | Additional Information | 5011 Ref | | --- | --- | --- | --- | --- | | | | Indicates that an additional information note is available | Additional information can be viewed by cursor enquiry under the Information (INFORM) or Textual Description (TXTDSC) fields | | | | | Non-tidal current direction | | H42 | | | | Spring tide – Ebb Flood | | H41 | | | | Light vessel/lightfloat | | P6 | | | | Daymarks | | Q82 | | | |
New Object – Point
New Object – Line
New Object – Area
New type of feature not yet known to ECDIS – further information available by cursor enquiry
Buoy = Sloping Beacon = Upright

Spar or pillar lateral beacons – red/green
IALA Maritime Buoyage System. Refer to NP 735
Q130 | | | | Symbol setting on ECDIS | | | | | | Simplified | Traditional | | | | | | | | | | | | | Buoys – lateral – conical – red/green, according to applicable IALA system | IALA Maritime Buoyage System. Refer to NP 735 | Q130.1 | | | | Lateral can buoys – red/green | IALA Maritime Buoyage System. Refer to NP 735 | Q130.1 | | | | Cardinal marks north/east/ south/west | IALA Maritime Buoyage System. Refer to NP 735 | Q130.3 | | | | Isolated danger marks | IALA Maritime Buoyage System. Refer to NP 735 | Q130.4 | | | | Safe water buoy | IALA Maritime Buoyage System. Refer to NP 735 | Q130.5 | | | | Spar or Pillar – special marks | Shape/topmarks ar

FAQs

What is the purpose of the ENC Symbols quick guide?

It helps you recognize lesser-known ENC symbols used with ECDIS. It is not intended to replace ECDIS Chart 1.

How can the same ENC symbols appear differently at night?

The guide notes that ENC symbols shown in daytime colours may be displayed in different colours/shades in the night-time palette.

Where can users find additional details for a symbol?

Additional information can be accessed through cursor enquiry, including notes under INFORM or TXTDSC fields, and examples can be found in ECDIS Chart 1.

Nov 1, 2026

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