Latitude

Imagine rings drawn around a ball.

One big ring goes around the middle. That is the Equator. Smaller rings go above it and below it. These rings are lines of latitude.

Latitude measures how far north or south of the Equator a place is. NOAA's National Ocean Service describes lines of latitude as imaginary lines that run east to west around Earth, but measure your distance north or south.

The Equator is the best-known line of latitude. It sits at 0 degrees and splits Earth into the Northern and Southern Hemispheres. The farther you travel north or south from the Equator, the bigger your latitude gets, until it reaches 90 degrees at each pole.

Latitude is the measurement of distance north or south of the Equator. NOAA's National Ocean Service puts the apparent paradox simply: lines of latitude run east to west, but they measure distance north or south. The Equator, at 0 degrees, divides Earth equally into the Northern and Southern Hemispheres, and latitude increases in both directions until it reaches 90 degrees at each pole.

A latitude is always given with a direction, N or S, because 30 degrees could be either side of the Equator. The North Pole is 90° N and the South Pole is 90° S. National Geographic Education describes 180 imaginary lines of latitude, 90 on each side of the Equator, each marking one degree.

Latitude lines never touch each other.

They stay the same distance apart, like the rungs on a ladder. Near the poles, the rings get small.

Lines of latitude are also called parallels, because they run parallel to the Equator and never meet. Each one is a circle around Earth.

The circles are not all the same size. The Equator is the biggest. National Geographic Education explains that because Earth is curved, the farther a circle is from the Equator, the smaller it is. At the North and South Poles, the circle has shrunk to a single point. But the parallels always stay the same distance apart, wherever you are.

Lines of latitude are called parallels because they are parallel to the Equator and to each other: unlike lines of longitude, which converge at the poles, parallels stay the same distance apart everywhere on Earth. A circle of latitude links all the points that share one latitude.

The circles themselves shrink toward the poles. National Geographic Education notes that, because of Earth's curvature, the farther a circle is from the Equator, the smaller it is, until at 90° N and 90° S it is simply a point. So the spacing between parallels stays constant while the length of each one shrinks, which is one reason a globe's grid looks the way it does.

We count latitude in degrees.

The Equator is 0. Each pole is 90. A place halfway to the North Pole is about 45 degrees north.

Latitude is measured in degrees, written with a small circle: 45° N means 45 degrees north. Each degree of latitude covers about 111 kilometers (69 miles) on the ground.

For more exact positions, each degree is split into 60 minutes, and each minute into 60 seconds. NOAA says a second of latitude covers only about 30.7 meters. National Geographic Education explains that seconds are precise enough for GPS to pinpoint a single building.

Latitude is an angle, measured in degrees from 0° at the Equator to 90° at the poles. One degree of latitude, called an arc degree, covers about 111 kilometers (69 miles). Each degree divides into 60 minutes, and each minute into 60 seconds. National Geographic Education gives a minute as about 1.8 kilometers; NOAA gives a second as about 30.7 meters.

Those small units matter. National Geographic Education notes that, using seconds of latitude, GPS devices can pinpoint schools, houses and even rooms. National Geographic Education's own example: Cape Town's latitude written as 33° 56′ S means the city is 33 degrees and 56 minutes south of the Equator.

Some latitude lines have names.

The Equator goes around the middle. Two lines called tropics sit on each side. Two more circles sit near the poles.

A few lines of latitude are so useful that they have names. NOAA's National Ocean Service explains that they are based on the Sun's position as Earth travels around it.

NOAA puts the Tropic of Cancer at roughly 23 degrees north, and the Tropic of Capricorn, at roughly 23 degrees south, mark the edges of the tropics. The Arctic Circle and the Antarctic Circle, at roughly 66 degrees north and south, mark the edges of the Arctic and Antarctic regions.

Several parallels are named because of the Sun's position during Earth's orbit, and NOAA notes they help us understand climate, weather and ocean currents. The Tropic of Cancer and the Tropic of Capricorn are the boundaries of the tropics; National Geographic Education gives them as 23° 26′ 21″ N and S, the northernmost and southernmost latitudes where the Sun can be seen directly overhead during a solstice.

The Arctic Circle and Antarctic Circle lie at roughly 66 degrees north and south and mark the boundaries of the Arctic and Antarctic regions. Note the difference in precision: National Geographic gives the tropics to the second of arc, while NOAA rounds all four lines to whole degrees. The tropics and polar circles each have their own topics in the encyclopedia.

Long ago, sailors looked at the stars.

One star, the North Star, helped them know how far north they were. Today, satellites help us too.

Sailors could work out their latitude long before they could find their longitude. NOAA explains that navigators measured the angle between the horizon and the Sun or the North Star. If the North Star was 60 degrees above the horizon, they were at 60 degrees north.

This was harder in the Southern Hemisphere, where the North Star cannot be seen. Today a group of more than 30 satellites helps receivers on the ground find their positions.

Latitude was measured reliably at sea hundreds of years before longitude, because, as NOAA explains, the calculations were simple. NOAA describes the method: measure the angle between the horizon and a celestial object, usually the Sun or the North Star. If the North Star stands 60 degrees above the horizon, the observer is at 60° N. In the Southern Hemisphere, where the North Star is not visible, the process was more complex.

Latitude is still monitored precisely. NOAA's National Ocean Service has tracked it since 1899, when a scientist with the U.S. Coast and Geodetic Survey built an observatory in Gaithersburg, Maryland, as part of a global project to monitor the wobble of Earth on its polar axis; other stations sat along the 39th parallel north. Satellite data replaced human observations in the 1980s.

Every place on Earth has a latitude.

Quito is very close to the Equator. Oslo is far to the north. Cape Town is far to the south.

Every place has a latitude. According to the Natural Earth map data, Quito in Ecuador is at about 0.2 degrees south, just below the Equator. Cairo in Egypt is at about 30 degrees north, and Oslo in Norway is at about 60 degrees north.

Cape Town in South Africa and Sydney in Australia are on different continents, but both are close to 34 degrees south. Places at the same latitude are the same distance from the Equator, even when they are thousands of kilometers apart.

City positions from Natural Earth, a free public map dataset, show how latitude sorts places by distance from the Equator: Quito, Ecuador, 0.21° S; Nairobi, Kenya, 1.28° S; Cairo, Egypt, 30.05° N; Oslo, Norway, 59.92° N; and Longyearbyen on Svalbard, 78.22° N. Cape Town and Sydney, on different continents, both lie close to 34° S.

Sharing a latitude means two places are the same distance from the Equator, however far apart they are east to west. Latitude is also only half an address. To pin a place down you need longitude as well, and the pair, called coordinates, locates any point on Earth.