Reading nautical charts, symbols, chart correction, and navigational publications.
Chart symbols and representation of direction and distanceChart correction from Notices to MarinersNavigational publications in common useAdmiralty (NP) publications and almanacs for passage making
8 guided lessons · 20 practice questions · 14 flashcards
3 outcomes · self-guided revision
Explain reading nautical charts, symbols, chart correction, and navigational publications.
Apply Chart symbols and representation of direction and distance to a realistic onboard situation.
Recall the core check: charts show depths, coastline, marks, hazards.
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Nautical Charts
A nautical chart is the mariner's map of the sea. It shows depths, coastline shape, navigation marks, hazards, and other essential information. Charts are drawn to Mercator projection, wi...
Charts use hundreds of standardised symbols defined in INT 1 (also known as Chart 5011 in the UK). Key categories include: depth contours and soundings, rocks and wrecks, buoys and beacon...
INT 1 (Chart 5011) — reference for all chart symbols
Blue = shallow water, White = deeper, Green = drying land
Charts must be kept up to date — new hazards, changed buoys, altered depths, and other changes are published in Notices to Mariners (NMs). Professional vessels correct charts weekly using...
Notices to Mariners (NMs) publish chart corrections
Always check chart edition date — older = higher risk of errors
Several publications supplement charts: the Nautical Almanac (e.g., Reeds or Macmillan's) contains tide tables, tidal stream atlases, port information, light lists, radio information, and...
Nautical Almanac — tide tables, lights, port info, radio (all-in-one)
Each chart has one or more compass roses printed on it. The outer ring shows True North (aligned with the chart grid). The inner ring shows Magnetic North, offset by the local variation....
The UK Hydrographic Office (UKHO) publishes a range of essential Admiralty publications, each identified by an NP number. NP5011 (the UK edition of INT1) is the definitive reference for a...
NP5011 (INT1) — chart symbols and abbreviations reference
Keeping charts up to date is a legal requirement for commercial vessels and a matter of safety for all mariners. The primary mechanism for chart correction is the weekly edition of Admira...
Weekly Admiralty Notices to Mariners (NMs) are the primary source of corrections
Permanent corrections are applied in waterproof violet ink
Electronic charts come in two main types. Raster Navigational Charts (RNCs) are essentially scanned images of paper charts — they look identical to the paper version but cannot be interro...
Raster charts (RNC) — scanned images of paper charts, cannot be queried
Vector charts (ENC) — database-driven, can be zoomed, queried, and customised
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