Latitude and Longitude

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If you take a look at a map or globe of the world, you may notice lines running east-west and north-south.  

The lines run east-west are known as lines of latitude.  The lines running north-south are known as lines of longitude.

Two globes showing lines of latitude (L) and lines of longitude (R).
Geographic lines of latitude and longitude. Image: Djexplo – Wikimedia Commons, public domain

Related: How to Remember the Difference Between Latitude and Longitude)

Latitude

While lines of latitude run across a map east-west, the latitude indicates the north-south position of a point on earth.  

Lines of latitude start at 0 degrees at the equator and end at 90 degrees at the North and South Poles (for a total to 180 degrees of latitude). Therefore, the higher the value of degree of latitude, the closer it is to the North or South Pole.

Lines of latitude. Image: Djexplo - Wikimedia Commons, public domain
Lines of latitude. Image: Djexplo – Wikimedia Commons, public domain

Everything north of the equator is known as the Northern Hemisphere and everything south of the equator is known as the Southern Hemisphere.

Distance Between Lines of Latitude

Lines of latitude are called parallels and in total there are 180 degrees of latitude.  The distance between each degree of latitude is about 69 miles (110 kilometers).  

What is a Parallel?

A parallel is a named line connecting all points along the same line of latitude.

For example, the 49th parallel marked part of the border between Canada and the U.S. that was negotiated by the United States and Britain as part of the Treaty of 1818:

It is agreed that a line drawn from the most northwestern point of the Lake of the Woods, along the 49th parallel of north latitude, or, if the said point shall not be in the 49th parallel of north latitude, then that a line drawn from the said point due north or south, as the case may be, until the said line shall intersect the said parallel of north latitude, and from the point of such intersection due west along and with the said parallel, shall be the line of demarcation between the Territories of His Britannic Majesty and those of the United States, and that the said line shall form the southern boundary of the said Territories of His Britannic Majesty, and the northern boundary of the Territories of the United States, from the Lake of the Woods to the Stony Mountains.

A section of map from 1846 showing the 49th parallel
A section of map from 1846 showing the 49th parallel. Map: A new map of Texas, Oregon and California, 1846, Library of Congress.

Major Lines of Latitude (or Parallels)

The five major parallels of latitudes from north to south are called: Arctic Circle, Tropic of Cancer, Equator, Tropic of Capricorn, and the Antarctic Circle.

Five major parallels of latitudes.  Image: NASA, public domain.
Five major parallels of latitudes. Image: NASA, public domain.

On a map where the orientation of the map is either due north or due south, latitude appears as horizontal lines.

Equator

The equator divides the earth into the Northern Hemisphere and the Southern Hemisphere is marks the location of 0 degrees latitude.   Latitude represents an angular distance north or south of the equator.

The equator marks the locations on earth that are equidistance from the North and South Poles.  

The equator crosses 78.7% water and 21.3% land and is about 24,901 miles (40,075 km) long.

The Equator is the line of zero degrees latitude around the middle of Earth.  Image: NASA, public domain.
The Equator is the line of zero degrees latitude around the middle of Earth. Image: NASA, public domain.

Tropic of Cancer

The Tropic of Cancer marks the location where the sun reaches the zenith at this latitude.  The exact latitude is not a fixed point and the latest measurement for 2014 is 23° 26′ 14.675″ (23° 26′ 16″).   

The summer solstice, which occurs on either June 20 or 21 of each year, marks the day on which the sun shines vertically over this parallel.

Map with the red line marking the Tropic of Cancer.
Map with the red line marking the Tropic of Cancer. Map: MediaWiki Commons.  

Tropic of Capricorn

Moving every year, the Tropic of Capricorn is the parallel line of latitude that is currently located at 23° 26′ 14.440″.

The winter solstice, which occurs on either December 21 or 22 of each year, marks the day on which the sun shines vertically over this line.

On this map, the Tropic of Capricorn is marked with a red line.
On this map, the Tropic of Capricorn is marked with a red line. Map: MediaWiki Commons.

Arctic and Antarctic Circles

The Arctic and Antarctic Circles are the parallels of latitude that are roughly 66.5 degrees (66° 33′ 44″ (or 66.5622°).

The region above the Arctic Circle, which includes the North Pole, is known as the Arctic.

The region south of the Antarctic Circle, which includes the South Pole, is known as the Antarctic.

Horse Latitudes

The Horse Latitudes are found at about 30 degrees North and South of the equator. Horse latitudes represents areas in the subtopics where prevailing winds diverge and flow towards the poles (known as westerlies) or towards the Equator (known as trade winds).

Map showing the location of horse latitudes.  Map: NOAA, public domain.
Map showing the location of horse latitudes. Map: NOAA, public domain.

Longitude

Longitude lines run north-south and mark the position east-west of a point. Therefore, latitude is the angular distance east or west of the Prime Meridian.

Lines of longitude run from pole to pole, crossing the equator at right angles. All lines of longitude are equal in length. Each line of longitude also is one half of a great circle.

There are 360 degrees of longitude (+180° eastward and −180° westward.).The longitude line of 0 degrees is known as the Prime Meridian and it divides the world into the Eastern Hemisphere and the Western Hemisphere.

Lines of longitude. Image: Djexplo - Wikimedia Commons, CC BY 2.0
Lines of longitude. Image: Djexplo – Wikimedia Commons, public domain

What is a Meridian?

While lines of latitude are known as parallels, lines of longitude are known as meridians.

How to Tell if a Meridian is East or West

Distances that that are west of the Prime Meridian are noted with a – in front of the number (negative numbers) and distances that are east of the Prime Meridian are positive numbers (-180 degrees degrees of longitude west and 180 degrees of longitude east).

Distance Between Lines of Longtitude

The distance between longitudes narrows the further away from the equator. As you move toward the poles, the distance between each line of longitude becomes smaller until the converge at the North and South Poles.

 The distance between longitudes at the equator is the same as latitude, roughly 69 miles. At 45 degrees north or south, the distance between is about 49 miles (79 km).

The distance between longitudes reaches zero at the poles as the lines of meridian converge at that point.

Lines of longitude converge at the poles where the distance between them in 0.  Lines of longitude. Image: Djexplo - Wikimedia Commons, public domain
Lines of longitude converge at the poles where the distance between them in 0. Lines of longitude. Image: Djexplo – Wikimedia Commons, public domain

Prime Meridian

The line of longitude where the degree is zero is known as the Prime Meridian.  Passing through the Royal Observatory, Greenwich, England, it is also known as the Greenwich Meridian and divides Earth into two equal halves known as the Eastern Hemisphere and the Western Hemisphere.  

Related: The Prime Meridian isn’t Where You Think it is

The prime meridian is the line drawn north to south at 0° (0 degrees) longitude. Credits: NASA
The prime meridian is the line drawn north to south at 0° (0 degrees) longitude. Credits: NASA

International Date Line

The line on Earth where one calendar day becomes the next is known as the International Date Line (IDL).  The line is generally found 180 degrees from the Prime Meridian but the line circumvents some regions and islands to avoid dividing contiguous pieces of regions and countries into two separate days.  

There are 23 one-hour slices and two 30 minutes slices that divide the world up into different time zones.  Traveling from east to west over the International Date Line advances the calendar by one day.

More: Geography of the International Date Line

The black line on this map shows the International Date Line. Map: CIA, public domain.
The black line on this map shows the International Date Line. Map: CIA, public domain.

Displaying Geographic Locations as Latitude and Longitude Coordinates

To provide a geographic location using latitude and longitude, a pair of numbers known as coordinates are used.   

Coordinates are composed of degrees, minutes, and seconds (DMS). When providing coordinates, Latitude is always written first. 

To provide the location of the United States Capitol building using latitude and longitude would be: 38° 53′ 35″ N, 77° 00′ 32″ W.  

Decimal Degrees, which converts the minutes and seconds portion of the coordinates, is another way to write coordinates. In stead of noting the cardinal directions (N,S,W, or W) in decimal degrees, points that are west of the Prime Meridian and south of equator are preceded by a negative sign.

Therefore, the United States Capitol’s coordinates in decimal degrees are 38.889722°, -77.008889°.

Aerial photograph of the U.S. Capitol building.
The US Capitol is located in Washington D.C. which is in Northern Hemisphere and the Western Hemisphere. Photo: NPS, public domain.

Many mapping programs such as Google Maps use DD.

Watch: Latitude and Longitude

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