True track is specifically measured from which geographical feature?

True track is specifically measured with reference to the meridians of longitude. This is because true track represents the actual path over the ground that an aircraft follows, and it is usually expressed in degrees from true north. Meridians of longitude provide a system that divides the globe into longitudinal lines to enable accurate measurement of angles east or west of the prime meridian.

In contrast, the equator and lines of latitude primarily relate to positions north or south of the equator but do not directly influence the measurement of true track, which is an east-west concept. The geographic poles are reference points for defining latitude but do not relate to the directional tracking of an aircraft. Therefore, the link between true track and meridians of longitude is what makes this answer correct, as it directly defines how an aircraft's track is oriented within the global navigation system.