The horizontal (east-west) lines, or circles, on a globe or map are called parallels of latitude. The equator, or the largest circle half way between the two points were the globe is attached to its stand, is a special parallel that is designated as the zero degree latitude. As viewed from the center of the Earth, latitude is measured in degrees of separation from the equator. Ashton MD, for instance, is at N39.14° latitude, which means that it is separated from the equator by 39.14°. The Earth’s north pole, which would be directly overhead for an observer at the center of the Earth, is at latitude N90°.
© James R. Johnson, 2015.