I didn’t even know that declination was a word.
Also did you know that:
As well as the magnetic deviation east or west, compasses also show a vertical “dip” up and down. This dip varies in different parts of the world and compasses are specially calibrated for that dip. So you can’t take a compass made for North America and use it in South America and get accurate readings.
Of course, there is this new GPS technology I keep hearing about, but you can’t use that in adventure racing.