To convert true heading to magnetic heading, what should be done with the variation?

To convert true heading to magnetic heading, understanding the concept of magnetic variation is crucial. Magnetic variation, also known as declination, is the angle between true north (geographic north) and magnetic north. This variation can either be easterly or westerly, depending on the geographic location.

When you encounter easterly variation, it indicates that magnetic north is located east of true north. In this case, to convert true heading to magnetic heading, you need to subtract the easterly variation because the magnetic heading will be to the left when moving from true north to magnetic north.

Conversely, if there is westerly variation, it means that magnetic north is located west of true north. In this scenario, you would add the westerly variation since it requires you to move to the right from true north to magnetic north.

Since the correct approach in this context is to address both easterly and westerly variations as a single method for conversion, you subtract easterly variation and add westerly variation, which is articulated in the chosen answer. This combined procedure ensures that you accurately calculate the magnetic heading from the given true heading based on the specific magnetic variation for your location.