Latitude and Longitude
How the coordinate grid works, with key lines and a worked example.
Latitude and longitude form a grid that lets us describe any location on Earth with two numbers.
Latitude
Latitude measures how far north or south a place is from the equator, in degrees. The equator is 0°. The North Pole is 90° N and the South Pole is 90° S. Lines of latitude are also called parallels because they run parallel to the equator.
Key lines of latitude:
- Equator: 0°
- Tropic of Cancer: about 23.4° N
- Tropic of Capricorn: about 23.4° S
- Arctic Circle: about 66.6° N
- Antarctic Circle: about 66.6° S
Longitude
Longitude measures how far east or west a place is from the prime meridian, which passes through Greenwich, London, at 0°. Longitude ranges from 0° to 180° E and 0° to 180° W. The 180° line is roughly where the International Date Line lies, with deviations.
Lines of longitude are called meridians and run from pole to pole.
Reading coordinates
Coordinates are written latitude first, then longitude. For example, 40° N, 74° W is a point in the northern hemisphere and western hemisphere, near New York City.
Degrees, minutes and seconds
A degree is divided into 60 minutes, and a minute into 60 seconds. Many maps and devices also use decimal degrees: 40.5° is the same as 40° 30′.
Time and longitude
Earth rotates through 360° in about 24 hours, so 15° of longitude corresponds to about one hour. Time zones are based on this but follow political boundaries too.
Common mistakes
- Reversing latitude and longitude.
- Forgetting N/S and E/W labels.
- Thinking lines of longitude are parallel. They meet at the poles.
Quick recap
Latitude is north–south from the equator; longitude is east–west from the prime meridian. Always give latitude first and include direction.