True north

From Glossary of Meteorology

true north

The direction from any point on the earth's surface toward the geographic North Pole; the northerly direction along any projection of the earth's axis upon the earth's surface, for example, along a longitude line.

Except for much of navigational practice (which uses magnetic north), true north is the universal 0° (or 360°) mapping reference. True north differs from magnetic north by the magnetic declination at that geographic point.