Magnetic heading offset

[gildas declercq]

Hi all

if the compass on my tablet is showing 166 cap, 
is it correct that pypilot should show the same ?

off course I put the tablet in the position that is aligned with the boat

thanx a lot    

[Jean-Marc Douroux]

Yes, of course, if the tablet provides a magnetic bearing.

It's also essential that, during the heading measurement on the boat, the tablet is kept away from any metallic or magnetic objects.

It's also best to check the tablet by comparing a bearing on the map (bearing with magnetic declination correction) with the bearing measured with the tablet.

[gildas declercq]

thanks , yes tablet was away from magnetic distrubance.

I am now working on the question of declination correction. I understand the concept, but not sure how to take it into account.

[seandepagnier]

how do the two magnetic headings compare at different headings?

Clearly they use different algorithms, and either could be re calibrated.

As for pypilot, as long as the heading is somewhat correct in a relative sense it can hold a course which is the most important function. For absolute accuracy you can adjust with a heading offset, but if this is incorrect at different headings it is an issue of calibration or magnetic interference.

If rotating 90 degrees you are 95 degrees difference it is fine for autopilot, and 88-92 (2 deg error) is as good as the sensors will typically perform anyway.