The distance covered by 1 degree of longitude at the Equator is approximately:

At the Equator, one degree of longitude covers about 111.3 km. This is obtained by dividing the Earth's equatorial circumference (about 40,075 km) by 360 degrees.

Calculation:

• 40,075 km / 360 = about 111.3 km.
• In miles, this is about 69 miles.

Why the distance between longitudes changes:

• Lines of longitude (meridians) run from the North Pole to the South Pole.
• They are farthest apart at the Equator and come closer together towards the poles, where they all meet.
• So, the length of one degree of longitude decreases as one moves towards the poles.

Formula:

Length of 1 degree of longitude at latitude x = 111.3 km x cos (x).

Examples:

• At the Equator (0 degrees): about 111 km.
• At 30 degrees latitude: about 96 km.
• At 45 degrees latitude: about 79 km.
• At 60 degrees latitude: about 56 km (about half the value at the Equator, since cos 60 = 0.5).
• At the poles (90 degrees): 0 km.

Length of one degree of latitude:

• Lines of latitude (parallels) are parallel to each other, so the distance between them stays almost the same.
• One degree of latitude is about 111 km everywhere.
• Because the Earth is slightly flattened at the poles, a degree of latitude is a little longer near the poles (about 111.7 km) than at the Equator (about 110.6 km).

Smaller units:

One degree is divided into 60 minutes, and one minute into 60 seconds.

One minute of latitude is about 1.85 km, which is the length of one nautical mile. This is why nautical miles are used in sea and air navigation.

Uses:

These measurements are used in map-making, navigation and calculating distances using coordinates.

Why not the other options?

• ✗180 km and 1,600 km do not match the length of a degree at the Equator.
• ✗Good to know
• ✗69 is the approximate value in miles, not kilometres.