# What Are Latitude and Longitude Lines on Maps?

## Parallels and Meridians

A key geographical question throughout the human experience is, "Where am I?" In classical Greece and China many years ago, attempts were made to create logical grid systems of the world to answer this question. The ancient Greek geographer Ptolemy created a successful grid system and listed the coordinates using latitude and longitude for significant places throughout the known world in his book Geography.

But it wasn't until the Middle Ages that the latitude and longitude system he developed was refined into what it is today. This system is now written in degrees, using the ° symbol. Read about the imaginary lines that divide the earth known as latitude and longitude.

## Latitude

Latitude lines run horizontally on a map. They are also known as parallels since they are parallel and equidistant from each other. Lines or degrees of latitude are approximately 69 miles or 111 km apart, with variation due to the fact that the earth is not a perfect sphere but an oblate ellipsoid (slightly egg-shaped). To remember latitude, imagine the lines as horizontal rungs of a ladder, "ladder-tude", or by the rhyme "latitude flat-itude".

There is both a north and south set of latitude degrees that run from 0° to 90°. The equator, the imaginary line that divides the planet into a northern and southern hemisphere, represents 0°. The degrees increase in either direction from this marker. 90° north is the North Pole and 90° south is the South Pole.

## Longitude

The vertical lines on a map are called longitude lines, also known as meridians. Unlike latitude lines, they taper (latitude lines are completely parallel, almost as if stacked on top of each other). They converge at the poles and are widest at the equator. At their widest points, these are about 69 miles or 111 km apart like latitude lines.

Longitude degrees extend 180° east and 180° west from the prime meridian, an imaginary line dividing the earth into an eastern and western hemisphere, and meet to form the International Date Line in the Pacific Ocean at 180° longitude. 0° longitude falls in Greenwich, England, where a physical line showing the division between the Eastern and Western hemispheres was constructed.

The Royal Greenwich Observatory was established as the site of the prime meridian by an international conference in 1884 for navigational purposes.

## Using Latitude and Longitude

To precisely locate points on the earth's surface, use latitude and longitude coordinates. Degrees are divided into 60 equal parts called minutes (') and those are further divided into 60 equal parts called seconds ("). Do not confuse these units of measurement with units of time.

Seconds can be broken down into tenths, hundredths, or even thousandths for the most precise navigation. Degrees latitude are either north (N) or south (S) and degrees longitude are either east (E) or west (W). Coordinates can be written as DMS (degrees, minutes, and seconds) or decimals.

### Example Coordinates

• The U.S. Capitol is located at 38° 53' 23" N, 77° 00' 27" W.
• That is 38 degrees, 53 minutes, and 23 seconds north of the equator and 77 degrees, 0 minutes, and 27 seconds west of the meridian.
• The Eiffel Tower in Paris, France is located at 48.858093 N, 2.294694 E.
• In DMS, this is 48° 51' 29.1348'' N, 2° 17' 40.8984'' E or 48 degrees, 51 minutes, and 29.1348 seconds north of the equator and 2 degrees, 17 minutes, and 40.8984 seconds east of the meridian.
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