What name is given to the baseline on a map from which latitude is calculated, having zero degrees latitude and equidistant from the poles?

• A. Prime Meridian
• B. Tropic of Cancer
• C. Equator
• D. International Date Line

Answer: (C)

Latitude is measured from a line that runs around the Earth’s middle called the equator. The equator is an imaginary circle exactly halfway between the North and South Poles, so it sits equidistant from both poles. Because it sits right there, it is defined as 0 degrees latitude—the baseline for all latitude measurements. From there, latitude increases as you move north up to 90 degrees at the North Pole, and south up to 90 degrees at the South Pole. The Prime Meridian is the zero line for longitude, not latitude, while the Tropic of Cancer is a specific circle of latitude at about 23.5°N, and the International Date Line is a longitude line near 180°, not a latitude baseline.