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##### Q and A video streaming session (31 Mar 2020)

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Stuart

× Welcome to the CPL Navigation question and answer forum. Please feel free to post your questions but more importantly also suggest answers for your forum colleagues. Bob himself or one of the other tutors will get to your question as soon as we can.

## Problems working out compass deviation

• Posts: 1

### gregbrowning created the topic: Problems working out compass deviation

Hi all,
I have a question regarding compass deviation. I've just started working through Bob's Nav Workbook and have realised that I don't know how to calculate the precise compass heading.

Obviously, when the compass deviation card says something like this:

For M: 030 060
Steer C: 028 058

I understand that the course will always be 2 degrees less. E.g. for 025 M, you need to steer 023.

However, what if the numbers are not separated by 30.
For example, in the Nav workbook:

For M: N 030
Steer C: 000 028

For 022M it says steer 021 (I wrote steer 20)
But for 027M steer 027. (I wrote steer 25)

I made many mistakes due to not knowing how to round up or down here.

Cheers,
Greg

• Posts: 2066