The latitude specifies a location's distance north or south of the equator. The longitude specifies the location's distance east or west from an imaginary line connecting the North and South Poles, called the Prime Meridian.
Latitude and longitude are used together to specify the geographical coordinates of a location on Earth. Latitudes, represented by the Greek letter phi (
?
), are called parallels and longitudes, denoted by the Greek letter lambda (
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), are called meridians. 
A perspective view of the Earth showing how latitude (?) and longitude (?) are defined on a spherical model. The graticule spacing is 10 degrees.
Measurement and Values
Latitude and longitude are both measured in degrees, minutes and seconds. There are 60 minutes in each degree and 60 seconds in each minute.
Latitude and longitude values on earth.
Image courtesy NASA
Values for longitude range from 0 (for the Prime Meridian) to 180 degrees. They are denoted by the letters E or W to represent direction. Alternatively, positive values may be used east of the Prime Meridian and negative in the west.
They range from 0 (for the Equator) to 90 (for the north and south poles). Latitudes are not only parallel but equidistant; degrees of latitudes are all roughly 69 miles apart. Values for latitude are positive in the Northern hemisphere and negative for the Southern hemisphere. Alternatively, the letters N and S may be used to denote the location.
Measuring longitudes and latitudes
The reason longitudes range from 0 to 180 and latitudes from 0 to 90 will become clear if you watch this video about how they are measured.
The Prime Meridian passes through the Royal Observatory in Greenwich, UK. Meridians are drawn in such a way that at the equator, the angle between the lines connecting both meridians to the center of the earth is one degree.
The latitude of a location is measured by observing the inclination of the sun or the position of known stars in the sky and calculating the angular distance from the horizon to them. Notable latitudes and longitudes
Besides the equator, four other parallels are of significance:
- Arctic Circle: 66° 33? 39? N
- Tropic of Cancer: 23° 26? 21? N
- Tropic of Capricorn: 23° 26? 21? S
- Antarctic Circle: 66° 33? 39" S
The region between the Tropic of Cancer and the Tropic of Capricorn is called the tropics. It is a region characterized by hot and humid climate. The sun is directly overhead at noon only in the tropics. The region between the tropics and the Arctic or Antarctic circles is called the Temperate zone and is characterized by four distinct seasons.
During the winter solstice (December), the sun is directly overhead the Tropic of Capricorn and the region south of the Antarctic circle experiences 24 hours of daylight. At the same time, the region north of the Arctic circle experiences 24 hours of night time. The situation is reversed during the summer solstice when the sun is directly overhead the Tropic of Cancer.
The most important longitudes are the Prime Meridian (0°) and the International Date Line (180°). They are at opposite sides of the Earth. The International Date Line marks the place where each day officially begins. So at the International Date Line, the west side of the line is always one day ahead of the east side. This is because the direction of rotation of the Earth is west to east. The Prime Meridian marks the location for the Coordinated Universal Time (UTC) or Greenwich Mean Time (GMT). Other time zones are denoted with offsets (positive or negative) from GMT/UTC.
In everyday life, the longitude for a location can be approximated using the time difference between that location and UTC. The sun moves across the sky at a rate of 15 degrees per hour (360°/day). So if the time zone is three hours ahead of UTC then that location is near 45° longitude (3 hours × 15° per hour = 45°). Longitudes converge at the Poles so calculations that are accurate for other positions may be inaccurate at the Poles.
Comparison chart
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Latitude
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Longitude
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Direction:
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East-west, parallel to
the equator
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North-south;
converging at the poles and widest at the equator
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Range:
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0 to 90° North and
South
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0 to 180° East and
West
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Time zone:
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Locations that share
the same latitude do not necessarily fall into the same time zone
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All locations on the
same longitude fall in the same time zone
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Parallel lines:
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Yes
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No
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Denoted by:
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Greek letter phi (?)
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Greek letter lambda
(?)
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Hemisphere:
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All locations along a
common latitude fall in the same hemisphere of the earth (northern or
southern)
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Locations along a
common longitude may be in different hemispheres.
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Denotes distance from:
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equator (north or
south)
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Prime Meridian (east
or west)
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