The heading sensor status light was blinking slowly, as it has done many times in the past without such an error in course. Total compass error is the combination of both deviation and variation declination and the rule is: I'm fortunate in that my primary compass is mounted externally in one bulkhead port and my electronic instruments are externally and flush mounted in the opposite bulkhead. Professional compass adjusters tend to only adjust a compass if its over degrees out. In the past, I have been able to pick out a mark on my navigation program and tell the auto pilot to take me there which it has, many times but no longer. Now you are prepared for that dark night, the faulty GPS or the thunderstorm. There are several methods for doing this but in general terms the procedure is as follows:
Compasses for Boat Navigation
IO, my apologies, the headwind effect is indeed second order, as you said all along. Magnets are aligned fore and aft and athwartships to create horizontal magnetic fields to compensate for the permanent horizontal components of the ship's magneti sm. Turn On to a New Course. Covered in most PPL courses, I think! But you need zero wind. Cross Over a Contour Curve. Obviously, the same thing will happen to a Southern Hemisphere compass when it goes to the north.
Swinging a compass
Can remember growing up we did everything off compass course, speed, time and ranges finding your location. When you want to swing your magnetic "backup" compass, you can do it even in harbor as you swing around a mooring. With this information we could then create a deviation card. For a given geographic area, there is always a disparity between true north and magnetic north. Magnets are aligned fore and aft and athwartships to create horizontal magnetic fields to compensate for the permanent horizontal components of the ship's magneti sm. Most of the time it is really close, but sometimes it's not perfect.
Make sure there is no deviation at your chosen spot, by taking a bearing of a chartered transit and checking it on the chart. Obviously, if the bearing changes choose somewhere else and try again but it's normally possible to find a place often up by the backstay which is deviation clear for the handbearing compass. If you're getting deviaiton, first make sure there's nothing you can do about it either by moving the compass or by moving something else. Click here to download WindCheck's May issue. Program this as a waypoint. How to Perform Compass Compensation - Ritchie. Compass performance should be monitored by frequently recording deviations in the compass deviation book.