Along the lines of longitude, the numbers measure latitude. They range from 0 degrees at the equator to 90 degrees at the north (90˚N) or south (90˚S) poles.
Lines of longitude range from 180 degrees east of the prime meridian to 180 degrees west of the prime meridian. Of course, 180˚E and 180˚W are the same longitude line.
Lines of longitude range from 180 degrees east of the prime meridian to 180 degrees west of the prime meridian. Of course, 180˚E and 180˚W are the same longitude line.