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SKYSAIL NAVIGATION AND SEAMANSHIP SKILLS CHARTS - including Course to Steer, EP, Tides, weather, etc

Nautical Chart Corrections - Keeping charts up to date                     

pdf version - chart correction

Changes in buoyage and lights, wrecks, obstructions or depth changes are examples of updates to charts that are critical to safe navigation.  Major changes covering a large area will require a new edition of the chart to be published, but when small important changes can be made by hand on the chart, the corrections are issued as a Notice to Mariners (NM or Notam), or a stick on Notice to Mariners Block.

NMs are online at  and are also issued in 'Practical Boat Owner' and 'Motor Boats Monthly'. The UKHO and Admiralty Chart Agents keep their stock of standard paper charts corrected  and it is good practice for all chart users to do so after purchase.

Correcting the Chart

1.   Decide if the notice is applicable to your chart, your vessel, and your sailing area.

2.  Apply the correction.  If replacing a symbol, find the old symbol on the chart, then, as close as possible and not over any other information, draw the new symbol (Check Chart 5011).  Link the new symbol to the required position with a curved line. Finally draw 2 diagonal lines through the old symbol to show that it no longer applies. 

If inserting a new symbol, draw it on the exact position given in the NM. If there is no room follow the process above for a 'replacement symbol'.

Detailed instructions and examples of chart corrections are in the UKHO publication NP294 ‘How To Correct Your Charts The Admiralty Way.’

3.  Document the corrections applied.  Check your work and make a note of the Notice to Mariner Number and Year in the bottom left hand corner of the chart, so any reader knows the last correction applied.  If you decide that a correction does not apply to your vessel, making a note of the correction number on the chart will save re-checking at a later date. 

 Notice to Mariners - Example below:

The title in bold is the NM number, the geographical area, a region or port and the type of correction. The second line gives the text of the correction, with instructions on the update.  In this case, a new starboard hand mark has been placed at position 50 20'.750N,  4 37'.820W, and an amended light has been notified at 50 19'.69N,  4 38'.66W, in Fowey harbour.

You need a pen with a fine point (preferably magenta in colour to show up clearly), Chart 5011 Symbols and Abbreviations, Internet access to or a list of Notices to Mariners.

The Notes contain any relevant further information. There follows a list of charts affected by this update and the last NM that applied, shown in square brackets [ ]. This allows you to check if there are any other outstanding corrections for the chart, as it is important to apply corrections to the chart in order. Below this is the source of the information and the UKHO reference.  For more information on updating your charts, and how to update Leisure Folios, refer to

3579* ENGLAND, South Coast - Fowey Harbour - Polmore Point and Saint Catherine's Point - Beacon; Light

Insert            Starboard hand beacon with topmark                 50 20'.750N,  4 37'.820W.

Amend          Light to Fl R7s15m2M                                       50 19'.69N,  4 38'.66W.

Note: The above update will he included in a New Edition of Chart 1185 to be published in due course.

Note: Positions on the chart affected by this notice are referred to a WGS 84 compatible datum. See ADMIRALTY CHARTS OF GREAT BRITAIN THAT ARE REFERRED TO A WGS 84 COMPATIBLE DATUM (near the beginning of this publication) and NM 4731(P)/00.

Chart [Last correction] - 31 (INT 1721) (plan C, Fowey Harbour) [ New Edition 24/5/01
Light List Vol. A, 2002/3, 0083
Fowey Harbour Commissioners Notice 1/02    (HH.232/470/03).

Posted 18th January 2012