Navigation Manuals – amendments

We are continually improving our materials. Please make the following amends in your books:

If you have attended a course/purchased the manuals prior to:

January 2023 (3 changes)



Heights beneath bridges were previously measured from Mean High Water Spring) (MHWS). Refer to the diagram. They are now measured by Highest Astronomical tide (*HAT).

Objects (as per the diagram) are still measured via MHWS.

From the Hydrographic Office (a useful site to look around):

Vertical and safe clearances of any overhead structure should be referenced to Highest Astronomical Tide (HAT).
All other heights must be referenced to either Mean Higher High Water (MHHW) or Mean High Water Springs (MHWS),
depending on the area concerned, as determined by the Tides and Geodetic Section.

Don’t forget to allow for rain and air pressure changing the height of rivers!

*HAT: The highest level of water that can be predicted to occur under average meteorological conditions and any combination of astronomical conditions.


The Deviation card on page 11 of the Q&A manual, has an additional Magnetic column that was inadvertently attached to the Compass and Deviation columns. Please delete/disregard the Magnetic column in its entirety. It is not supposed to be there and does not match/relate to the rest of the Deviation card, and is therefore incorrect. This column is not required to carry out any of the practice questions.

Q&A book page 54
Question 19 (b) answers:
Answer (b) should read: 20°39.05’S 148°50.2E
(Summary: the longitude must be updated)



If you have attended a course/purchased the manuals prior to:

July 2020

Navigation – Main Manual:
Questions and examples have been updated, please print the follow pages and insert them into your manuals.
True to Compass amendments pages 57-60

Pages 68 and 69

Navigation – Q&A Manual:

Page 14: Ex10 WEST side of Petrel Island not the East

Page 20/21: Please fix/glue the following two pages on top of page 20/21 : Ex 16 pages 20/21 amendments

Page 47: Exercise 16 Answers: DR, 3-bearing fix and Set/Drift

Page 48: 3a CTS answer should read 339°C


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