In this section, we want to share a little bit of our experience in chart corrections. The following examples are one way to perfom them. We hope to ease your task when comes the time for you to update your charts. This page can be considered as a complement to the ADMIRALTY NP 294 “how to correct your charts the ADMIRALTY way”. We use ADMIRALTY notices to mariners printed on tracing paper in our examples. ADMIRALTY Videos are also available on the ADMIRALTY TV


My tools for chart corrections

This are the tools i daily use for correcting charts:

  • 0.25 magenta pen, the only one authorized for chart corrections
  • 2B pencil and eraser
  • A screw: my option to mark the corrections positions on the charts. 7H pencil is recommended by the ADMIRALTY
  • A compass where the magenta pen fits
  • A ruler and a circles template (very useful)
  • A NP5011 (when i have a memory loss on symbols and abbreviations)
  • Tracing paper to print the corrections
  • chart availability list to check the last edition date to prevent correcting a withdrawn chart
  • to see all the nms for a chart reference
  • NP133A, the chart maintenance catalogue to record all the updates per chart
  • Notices to mariners

Bottom left of the chart


Informacion at the bottom left on an ADMIRALTY chart

In this section of the charts appears:

  • The last edition date of the chart. This can be verified with the chart availability list. if the date is older than the one on the list, the chart needs to be replaced.
  • A QR code that redirect you directly to the web to see the nm nº affecting this reference.
  • All the notices to Mariners nº applied on the chart should be written after the text “ADMIRALTY notices to mariners updated to”

Updating the nms list

The last nm nº written on the chart correspond to the one on the tracing paper.
No corrections missed.
We can then update our “nm list” with the 2 nm numbers we have just apply.

Notices to mariners on tracing paper

Top section of a tracing ntm
  1. Chart reference (or nº)
  2. Edition date of the chart
  3. Position of the correction on the chart
  4. Current notices to mariners number
  5. Previous notices to mariners number that should appear on the bottom of the chart
  6. ADMIRALTY charts are grouped in Folios which represent an area on the map. In this example, Folio 25 is part of the mediterranean.


Example 1

position the tracing paper on the chart
Mark the position of the buoy on the chart
The buoy should be drawn in this exact position
To avoid deleting information, we draw our buoy in clear space
A non direct arrow will connect our buoy to it’s position. Arrows on ADMIRALTY charts have specific signification. that is why it is recommended to use S type arrows in this type of situation.

Example 2

Tracing positioned on the chart. Lack of space to draw the buoy.
Using 7H pencil or other tool to mark the spot
As we have a clear space just above our mark, we can draw our buoy there and connect it to it’s spot with a non direct arrow.
objects should always be at 2cms radius max from the spot

Example 3 – deleting a buoy

The sign atthe end of te arrow is the DELETE symbol. We have to delete the buoy and it’s characteristic.
We recommend to use the ruler for a clean job

Example 4 – deleting and adding new information

In this example, 5 buoys to place in an area with a lot of informations.
positions of the 5 buoys we’ll have to draw with text associated
Only 1 buoy can be drawn on it’s spot. The others have been drawn in clear space with a non direct arrow to connect to their positions

Example 5

In this example, we have a lot of space outside the compass but the position is inside it. In this case it is better to draw the buoy inside the compass and connect this way.
Always keep in mind to avoid writing on existing information.


Example 1

This is the light information we have to modify
Only the range of the light needs to be replaced.
We then have to delete 13/10M range with double line and write the new one under due to lack of space

Example 2 – deleting, moving and amending a light

This is the light we have to update. Not a lot of space on top to write the new range.
We have to move the light, write the new range and delete the old one
We draw the new light on spot. As the range of the old one is useless, we delete it. We use the silicon ruler to draw a line to write the new range
And we don’t forget to delete the old light to avoid confusion

Example 3

Same spot for the light but different range. few space around
It is possible to write Fl(4)G.11s on top of the old range and keep the 13m5M of it.
We choose to write the new range under.
And delete the old one

Example 4

The position of the new light is just on top of some existing information.
It is not possible to draw this new light on it’s spot
We draw our light in the closest space available
Then we tie it to it’s position with an indirect arrow


We already show in the previous examples how to delete lights or buoys. Let’s see how to delete other types of informations and notes

Example 1

We have to delete an arc of visibility in this tracing
A few short double lines around the circle are enough

Example 2

this tracing represent the delete of a restricted area, the caption and the note associated.
Short double lines along the delimitation. One line is enough to delete the caption
Notes are deleted this way (left).
The elimination of a note is presented this way on the tracing (right)


Example 1

Several depths to insert and others to delete in this correction
In this picture we can see the positions for the new depths
Double lines to delete depths.
Undirect arrow to tie the depths to their positions when lack of space

Example 2

enclosed depht to be modified by the value 19
A little circle in the center of the enclosed depth will determine the position of the new value.
Short lines to delete the old value and an inderect arrow to tie the new value to the center of the enclosed depth.

Cables and lines

Example 1

Marine Reserve we have to draw on the chart.
We mark the different lines positions
We draw the lines with space for the captions.
No writing on existing information.
Result with description

Example 2

On this example we will have to draw an electrical cable and 2 water lines
Mark the lines positions and draw a guideline for the power cable with 2B pencil
Hacksaw blade can be used to draw the cable to gain time.
We don’t use it as it end up deteriorating the magenta pen.


Example 1

In this example, we have to draw a prohibited entry area.
We mark the position of the circle
Using the correct diameter, we can draw our line leaving space for the “prohibited” symbols

Example 2

Restricted area around wreck and fishing prohibited sign
Marking positions
Using the circle template

Example 3

The compass will be used to draw this circle
Fisrt we have to find the center as it is not shown on the tracing. here is one way to do it using the circle’s diameter.
After marking the center and some reference points on the charts we draw the circle and the prohibited symbols
We end the update by writing the caption, sticking the note and writing the nm number at the bottom left of the chart