What are longitude and latitude and how they work?

Greek geographer Ptolemy created a grid system and listed the coordinates for places throughout the known world in his book Geography.
Anyway, Lines of latitude measure north-south position between the poles. The equator is defined as 0 degrees, the North Pole is 90 degrees north, and the South Pole is 90 degrees south. Lines of latitude are all parallel to each other, thus they are often referred to as parallels. The memory rhyme I use to help remember that lines of latitude denote north-south distance is: "Tropical latitudes improve my attitude".


Lines of longitude, or meridians, run between the North and South Poles. They measure east-west position. The prime meridian is assigned the value of 0 degrees, and runs through Greenwich, England. Meridians to the west of the prime meridian are measured in degrees west and likewise those to the east of the prime meridian are measured to by their number of degrees east.
The memory rhyme I use to help remember that lines of longitude denote east-west distance is: "Lines of LONGitude are all just as LONG as one another." With this saying in my mind, I picture all of the longitudinal meridians meeting at the poles, each meridian the same length as the next.