Variation and deviation, online Nav course, please help.

[jackdale]

Use a deck log

[auskiwi]

Originally Posted by Time2Go

True Virgins Made Dull Company, West is Best , Least is East

So when go from True to Magnetic to Compass
Virgins= Variation
Dull = Deviation
Therefore when going from True to Magnetic you Add West but Subtract East
and then when going further along from magnetic to compass you do the same
Variation you get from the compass rose
Deviation is different for every boat and every boat should have a deviation card
Cheers

Nice one, I was taught that one when I went to Marine School in NZ in about 1978.

[OldFrog75]

True Virgins Make Dull Companions so Add Whiskey (West)

I don't understand the OP and why some Variation or Deviation would be indicated as "- West"

[Hoofsmit]

On the original post it would seem you has deviation and variation confused, deviation does not increase or decrease annually in minutes. It is set by the errors on various points on the boats steering compass and noted on the boats deviation notes ( normally set out as a graph but referred to confusingly as the deviation chart ! and it relates only to that vessels compass)

The annual change of variation of magnetic compared to true north is found on the charts ( maps ) compass rose and varies between you position around the globe.

The - and + is a misnomer , the variation is east or west , then you apply the phrases (noted on others posts ) depending if you are working from the nav table to give a course to steer to the guy on the helm or you have taken a bearing when on deck and need to place that on the chart to find your position on the chart

Hope that helps


Sent from my iPad.......i apologise for the auto corrects !!!

[seaward 42]

"I seem to become greatly confused when they say you have to "subtract "E"...


That is correct, you will subtract E from True bearing/azimuth if you converting to Magnetic.
Also in case you have W variation but annually changing E. So if your variation in 2010 is 10° W but annually changing 1' East, for 6 years that is 6' so you should subtract those 6' E from 10° W and you will have 9° 54' and variation will still be W. like in this picture.

[fryewe]

Originally Posted by kevinnem

...I find this much more confusing then just learning how it works.

Can anyone either explain this to me...

The link below gives a good description of the geometry and offers a clear explanation of use of the memory aids and why the memory aids are useful.

Hope this helps.

Application of Error to a Compass