Compass Variation

The direction in which the compass needle points is called magnetic north.

In the eighteenth century, the angle between magnetic north and true north was recorded in logs and journals as 'the variation'. Today, the scientific name for this 'variation' is magnetic declination.

The existence of variation in the compass was well known by the early seventeenth century, and navigators sought to record the extent of variation wherever they sailed. By the mid-seventeenth century, this was usually done using an Azimuth Compass, and applying the variation discovered to the Mariner's or Sea Compass used to steer the vessel, thus revealing the true course of the vessel.