Longitude is the angle along the Earth's surface between the Prime Meridian and any point on the surface.
The 'lines' don't need to be measured.
prime meridian
The imaginary line is called the Prime Meridian.
The Prime Meridian is an imaginary line from which angles east and west are measured in order to help define and describe locations. The angle thus measured is called the location's 'longitude'.
The imaginary lines that run around the earth in an east-west direction are lines of latitude or parallels.
They are drawn on the earth as imaginary lines that run from east to west.
Lines of longitude are imaginary lines running from the North to the South Poles of the Earth. They are often referred to as Meridians. They are measured in terms of the angular distance east or west from the prime Meridian which runs through Greenwich, England.
Lines of Latitude
The imaginary lines that run east and west are called lines of latitude or parallels. They are used to measure how far north or south a location is from the equator, which is the line of 0 degrees latitude.
Imaginary lines that circle the earth from east to west are called lines of longitude, or meridians. These lines help define the distance east or west of the prime meridian, which is located in Greenwich, England.
latitude
latitude
The imaginary parallel lines that run east-west are called lines of latitude. These lines measure the distance north or south of the equator and are used to establish the location of a place on the Earth's surface.