The imaginary vertical lines that run from the North pole to the South pole on a map are called longitudinal lines. The Prime Meridian is the longitudinal line that has a value of 0 degrees. On a map, longitudinal lines are measured in increments of 15 degrees from the Prime Meridian. The antimeridian is the meridian that is 180 degrees east or west of the Prime Meridian. Together, the Prime Meridian and antimeridian form a vertical circle around the Earth and divide the Earth into the eastern and western hemispheres.
The imaginary horizontal lines on a map are called latitude lines. On a map, latitude lines are measured in increments of 15 degrees from the equator. The equator has a measurement of 0-degree latitude. It runs through the middle of the Earth. The equator is equidistant from the North and South poles. Thus, the equator separates the northern and southern hemispheres.