Where do I begin?

First, you need to find out whether or not your chart actually needs updating.  There are two ways of going about this.

If you have your computer switched on, you can go to UKHO and select ‘view update list by chart number’.  Insert the chart number into the box provided and it will give you a list of all of the corrections applied to that chart since the release of its latest edition.

Alternatively, if you have a smart phone you can download for free any QR code reader and read the QR code in the corner of your chart (older charts may not have a QR code, in which case you’ll have to search the first way).  Reading the QR code will take you directly to the results page of the nmwebsearch site.


You then need to compare the nm numbers with those written along the bottom of the chart.  If the chart has been corrected/updated by hand before, some of these will be handwritten.  Otherwise, they will be printed.


If there are no numbers missing, your chart is up to date.  If there are one or more numbers missing from the chart, these corrections need to be applied, by hand, in order to bring your chart up to date.

So….how do I work out what needs to be corrected?

Back to the NMwebsearch page showing your list of notices for your chosen chart.  Tick the box next to the notice that you need and select ‘view selection’.  This will then take you to the notice.


The alternative is to get your Notices to Mariners out .You can either buy them for £2.40 each or you can download them from the UKHO website.  On the front (top left-hand corner) of the paper one, you will find the notice numbers which are contained within that edition.  Find the correct edition then search by notice number for the correction.

The notice will then give you the co-ordinates and correction that you need to apply.


What do I use?

Chart Correction Pen - Corrections need to be done with violet ink using pen with an extremely fine nib.  The recommend nib sizes that the United Kingdom Hydrographic Office  suggest are 0.18mm to insert information and 0.25mm nib to delete.

It is important to use violet ink as this does not disappear under red lighting as is often used at night. (That’s fairly key, I’d say…)

Pencil – used to pinpoint the exact position of the correction.  Once you have made the correction in ink, you can erase this mark using a soft eraser.

Adhesive – some of the corrections are in the form of ‘blocks’ which need to be cut out from your Notices to Mariners and actually stuck onto the chart. You need to ensure that the adhesive you use will keep the block stuck onto the chart permanently.

Parallel rule and dividers – handy for getting the bearing of leading lights and anchoring areas accurately.  You can use a pencil to make the marks in the first instance and when you are satisfied that it is correct, go over in violet.

Hacksaw blade – no, it’s not for chopping up the charts when you’ve messed up or had enough!  They actually make very effective templates for drawing cables onto charts.  Try it!

Correction Template – Really handy for doing small circles that are too tiny for a pair of compasses.

Correction fluid – DO NOT USE!!!  If you make a mistake, two neat lines through the incorrect part and re-draw correctly.  Fluid could (a) hide stuff like soundings that are pretty vital (b) flake off in time, exposing the incorrect information.

How do I draw the symbols/move the marks/extend the sounding lines…….

There are a very diverse number of different corrections that you may need to make.  My recommendation is to get hold of a copy of NP294 – How to Keep your Admiralty Products up-to-date.


Another extremely useful publication is NP5011 – Symbols and Abbreviations used on Admiralty Paper Charts.


There is an easier way of course…….bring/send them to us and we can do it for you!!  Just give us a call for more details. If you want to keep up to date with future Seachest blogs on admiralty charts, give us a like on Facebook, or follow us through @seachestcharts.

Post By Nicole Sage