the great circle (of the earth) which lies in the plane of the celestial meridian of a place, and which passes through the place and the poles; also often applied to that half of this circle that extends from pole to pole through the place. So named because the sun crosses it at noon. A terrestrial globe, or a map of the earth or part of it, has usually a number of meridians drawn upon it at convenient distances, marked with figures indicating their respective longitude or angular distance on a parallel from the first meridian, i.e. the meridian (in British maps that of Greenwich) conventionally determined to be of longitude 0°., geograafilist põhja- ja lõunapoolust ning vaatluskohta läbiva tasandi ja maaellipsoidi lõikejoon. Samal meridiaanil paiknevatel punktidel on ühine geograafiline pikkus.