The graticule is the spherical coordinate system based on lines of latitude and longitude. A circle formed on the surface of a sphere by a plane that passes through the center of the sphere. The Equator, each meridian, and each other full circumference of the Earth forms a great circle. The arc of a great circle shows the shortest distance between points on the surface of the Earth. Linear scale Linear scale is the relation between a distance on a map and the corresponding distance on the Earth.
Scale varies from place to place on every map.
The degree of variation depends on the projection used in making the map. Each map projection has specific properties that make it useful for specific purposes. A rhumb line is a line on the surface of the Earth cutting all meridians at the same angle. A rhumb line shows true direction. Parallels and meridians, which also maintain constant true directions, may be considered special cases of the rhumb line.