Geography
Geographic Coordinate System
Quick fact
A single degree of latitude equals about 111 kilometers (69 miles), but a degree of longitude varies from the same at the equator to zero at the poles.
Why this is interesting
You can tell someone exactly where you are anywhere on Earth using just two numbers. How does a system of imaginary lines turn the entire planet into a precise address?
Read the full explanation
Understanding Geographic Coordinate System
Imagine slicing Earth like an orange. The horizontal slices are lines of latitude—parallel rings that measure how far north or south you are from the equator. The vertical slices (from pole to pole) are lines of longitude—meridians that measure how far east or west you are from the Prime Meridian in Greenwich, England. Together, they form a grid. Any point on Earth gets a unique pair: first latitude (north/south), then longitude (east/west). These numbers are usually given in degrees (°), minutes ('), and seconds ("), or in decimal degrees for convenience. For example, 40°42'46"N 74°00'21"W is the location of the Statue of Liberty.
A deeper explanation
The system works because Earth is (approximately) a sphere. Latitude is based on the angle from the center of Earth to a point on the surface relative to the equatorial plane—so 0° at the equator, 90° at the poles. Longitude is the angle east or west from the Prime Meridian, measured along the equator. The intersection of a latitude circle and a longitude meridian defines a unique point. This coordinate system is the backbone of navigation: when you use GPS, your device calculates its latitude and longitude from satellite signals. The system also underlies all digital maps—every place on Google Maps is stored as a coordinate pair. Understanding the coordinate system reveals how we can measure distances, create time zones, and even plan satellite orbits.