Geography
Geographic Coordinates
Quick fact
The system of latitude and longitude was refined by the ancient Greek astronomer Ptolemy, and the Prime Meridian was only internationally agreed upon in 1884.
Why this is interesting
You can find any place on Earth using two simple numbers—but how do those numbers work, and why do they never change?
Read the full explanation
Understanding Geographic Coordinates
Imagine Earth as a globe covered by an invisible net of lines. The horizontal lines are called parallels of latitude; they measure how far north or south you are from the equator (0°). The vertical lines are meridians of longitude; they measure how far east or west you are from the Prime Meridian (0°) that runs through Greenwich, England. Together, they form a grid—every point on Earth has a unique pair of coordinates (latitude, longitude). Measuring in degrees, each degree can be subdivided into 60 minutes, and each minute into 60 seconds for extreme precision.
A deeper explanation
Geographic coordinates are based on Earth's spherical shape and rotation. Latitude is defined by the angle between the equatorial plane and a line from Earth's center to a point on the surface. Longitude is the angle east or west from the Prime Meridian, measured along the equator. Because Earth rotates 360° in 24 hours, 15° of longitude corresponds to one hour of time difference—linking coordinates directly to time zones. This system is essential for GPS satellites, which calculate positions using precise timing and coordinate geometry. Understanding these coordinates unlocks global navigation, mapping, and geographic analysis.