Replacing one depth with another in the same position on an ADMIRALTY Standard Nautical Chart

Begin by using a grid box to reference the Noticeto Mariners (NM) position on the chart. Then, use the latitude and longitude guides on the tracing and the chart to accurately place the tracing over the exact location. The 'in lieu' instruction on the tracing indicates that the new depth will replace an existing one in the same position.

Using a 7H pencil, mark the center point of the depth that needs to be replaced. Remove the tracing to reveal the chart. With a magenta 0.18 pen, draw a small circle on the marked spot. Complete the deletion by drawing double strike-throughs over the existing depth surrounding the small circle.

After deleting the old depth, write in the new depth and link it with an arrow to the existing position. Lay the tracing back over the chart to confirm that the correct depth has been replaced. Once all updates are applied, add the NM update number to the chart's Notices to Mariners section in the bottom left corner.