Correcting charts based on the weekly Admiralty Notices to Mariners (NtM) is a critical process
to ensure navigational safety. Here's a detailed guide on how to correct charts, including
corrections with blocks.
Steps to Correct Charts Using Admiralty NtM:
1. Gather Necessary Materials:
o Latest Admiralty Notices to Mariners.
o Chart correction logbook.
o Appropriate navigational charts.
o Correction tools: dividers, parallel rulers, pencils, erasers, and a fine-tipped pen.
o Blocks (printed updates provided by the NtM).
2. Review the Weekly Admiralty NtM:
o Identify the section for chart corrections.
o Note down the chart numbers and specific corrections.
3. Cross-Reference with Onboard Charts:
o Compare the chart numbers listed in the NtM with the charts available onboard.
4. Record Corrections in the Logbook:
o Log each correction entry by chart number, NtM number, and date of correction.
5. Apply Corrections to the Charts:
o Follow the specific instructions provided in the NtM for each chart.
Example Correction Process:
Example Correction from NtM:
Chart No. 1234 - North Sea:
Correction: Addition of new wreck at position 54°10'N, 001°20'E.
Note: Update required in the vicinity of Teesport.
Chart No. 5678 - English Channel:
Correction: Amendment to traffic separation scheme near Dover.
Note: Changes to buoy positions and new reporting points.
Chart No. 9101 - Mediterranean Sea - Western Part:
Correction: Changes to depth contours near the Balearic Islands.
Note: New survey data incorporated.
Block: A block correction for an area on the chart.
Detailed Steps for Corrections:
1. Locate the Affected Area:
o Identify the precise location on the chart where the correction needs to be applied
using the coordinates or description provided in the NtM.
2. Addition of New Features:
o For new features like wrecks, use a pencil to mark the exact position.
o Once verified, use a fine-tipped pen to make the mark permanent. Add relevant
symbols and annotations as per the chart’s legend.
3. Amending Traffic Separation Schemes:
o Follow the instructions to redraw traffic separation lines or amend existing ones.
o Use dividers and parallel rulers for precise measurements and placements.
o Update buoy positions by marking the new locations and removing or amending
outdated ones.
4. Applying Block Corrections:
o Locate the Block: Blocks are provided as printed sections of the chart that
contain updated information.
o Cut the Block: Carefully cut out the block section along the printed lines.
o Position the Block: Identify the corresponding area on the chart.
o Attach the Block:
Place the block over the existing chart section to ensure it fits perfectly.
Use a light adhesive or tape to attach the block. Ensure no air bubbles or
misalignments.
o Verify Accuracy: Double-check that the block aligns correctly with surrounding
chart features.
5. Final Verification:
o Verify all corrections against the NtM to ensure accuracy.
o Cross-check with the correction logbook to confirm all updates are recorded and
applied.
6. Inform the Bridge Team:
o Notify the navigation officer and bridge team about the updated charts and any
significant changes affecting navigation.
Example Logbook Entry:
NtM Chart Applied
Date Correction Description Remarks
Number Number By
2024-08- Added new wreck at 54°10'N,
2023/32 1234 3rd Officer Verified
01 001°20'E
2024-08- Amended traffic separation
2023/32 5678 3rd Officer Verified
01 scheme near Dover
2024-08- Updated depth contours, applied rd Verified, block
2023/32 9101 3 Officer
01 block used
Conclusion:
Correcting charts using weekly Admiralty Notices to Mariners is a meticulous process that
ensures the accuracy and safety of nautical navigation. By following the steps outlined, including
the use of block corrections, mariners can maintain up-to-date charts that reflect the latest
navigational information.
