Deviation - Easterly or Westerly
 

Total Deviation on Heading = A + B Sin (@) + C Sin (@)
Now how to decide if this total deviation is Easterly or Westerly

Well, I presume the @ symbol means heading.

First, lets get the formula correct. IIRC there should be a Cosine term in there for coefficient C rather than sine.

Now... how do you know if its East or West? Easy. The formula will spit out a positive or a negative number: (A B and C can all be negative or positive and sin and cosine generate numebrs between -1 and +1.

If its positive the deviation is East, if its negative the deviation is west.

In fact, why even bother if its east or west:

Compass + Deviation = Magnetic

So forget about all that 'east is least, west is best' clap trap and just keep it as a positive or negative number and you are good to go.

pb

Thanks Capt
 

Thanks Capt thats nice explanation