convergence of meridians—The angular drawing together of the geographic meridians in passing from the equator to the poles. At the equator, all meridians are mutually parallel; passing from the equator, they converge until they meet at the poles, intersecting at angles that are equal to their differences of longitude. The term convergence of meridians is also used to designate the relative difference in the direction of the meridians at specific points on the meridians. Thus, for a geodetic line, the azimuth at one end differs from the azimuth at the other end by 180° plus or minus the amount of the convergence of the meridians at the end points.

–

Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

Part of LearnCST’s exam text bundle.