# latitude

Longitude (λ) Map of Earth Lines of longitude appear curved and vertical in this projection, but are actually halves of great circles. Lines of latitude appear straight and horizontal in this projection, but are actually circular with different radii. All locations with a given latitude are collectively referred to as a circle of latitude. The equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0.
Latitude, usually denoted symbolically by the Greek letter phi, , gives the location of a place on Earth north or south of the equator. Lines of Latitude are the horizontal lines shown running east-to-west on maps. Technically, Latitude is an angular measurement in degrees (marked with °) ranging from 0° at the Equator (low latitude) to 90° at the poles (90° N for the North Pole or 90° S for the South Pole; high latitude). The complementary angle of a latitude is called the colatitude.

## Circles of latitude

Main article: Circle of latitude

All locations of a given latitude are collectively referred to as a circle of latitude or line of latitude or parallel, because they are coplanar, and all such planes are parallel to the equator. Lines of latitude other than the Equator are approximately small circles on the surface of the Earth; they are not geodesics since the shortest route between two points at the same latitude involves moving farther away from, then towards, the equator (see great circle).

A specific latitude may then be combined with a specific longitude to give a precise position on the Earth's surface (see satellite navigation system).

### Important named circles of latitude

Besides the equator, four other lines of latitude are named because of the role they play in the geometrical relationship with the Earth and the Sun:
Only at latitudes between the Tropics is it possible for the sun to be at the zenith. Only north of the Arctic Circle or south of the Antarctic Circle is the midnight sun possible.

The reason that these lines have the values that they do lies in the axial tilt of the Earth with respect to the sun, which is 23° 26′ 21.41″.

Note that the Arctic Circle and Tropic of Cancer and the Antarctic Circle and Tropic of Capricorn are colatitudes since the sum of their angles is 90°.

## Subdivisions

As Earth is not a smooth sphere, but slightly oblate, a degree of latitude varies in length from about 111.3195 km at the equator to 110.9462 km at the poles. A degree of arc at a latitude not only varies with latitude, but also with the direction being faced. To simplify calculations where elliptical consideration is not important, the nautical mile was created, equaling exactly 111.12 km per degree of arc or, sub-dividing into minutes, 1852 metres per minute of arc. One minute of latitude can be further divided into 60 seconds. A latitude is thus specified as 13°19'43″ N (for greater precision, a decimal fraction can be added to the seconds). An alternative representation uses only degrees and minutes, where the seconds are expressed as a decimal fraction of minutes, thus the above example is expressed as 13°19.717' N. Degrees can also be expressed singularly, with both the minutes and seconds incorporated as a decimal number and rounded as desired (decimal degree notation): 13.32861° N. Sometimes, the north/south suffix is replaced by a negative sign for south (−90° for the South Pole).

## Effect of latitude

A region's latitude has a great effect on its climate and weather (see Effect of sun angle on climate). Latitude more loosely determines tendencies in polar auroras, prevailing winds, and other physical characteristics of geographic locations.

Researchers at Harvard's Center for International Development (CID) found in 2001 that only three tropical economies — Hong Kong, Singapore, and part of Taiwan — were classified as high-income by the World Bank, while all countries within regions zoned as temperate had either middle- or high-income economies.[1]

## Types of latitude

Because the Earth is slightly flattened by its rotation, cartographers refer to a variety of auxiliary latitudes to precisely adapt spherical projections according to their purpose.
More generally, for other planets such as Mars, geographic and geocentric latitude are called "planetographic" and "planetocentric" latitude, respectively. Most maps of Mars since 2002 use planetocentric coordinates.

### Common "latitude"

• In common usage, "latitude" refers to geodetic or geographic latitude and is the angle between the equatorial plane and a line that is normal to the reference spheroid, which approximates the shape of the Earth to account for flattening of the poles and bulging of the equator.
The expressions following assume elliptical polar sections with the angular eccentricity, (which equals , where and are the equatorial and polar radii), and that all sections parallel to the equatorial plane are circular. Geographic latitude (with longitude) then provides a Gauss map. Utilized in some of these conversions is a common elliptic integrand:

:

### Reduced latitude

• Reduced or parametric latitude, , is the latitude of the same radius on the sphere with the same equator.
:

### Authalic latitude

• Authalic latitude, , gives an area-preserving transform to the sphere.
:

:

### Rectifying latitude

• Rectifying latitude, , is the surface distance from the equator, scaled so the pole is 90°. Unfortunately, it involves elliptic integration:
:

::

### Conformal latitude

• Conformal latitude, , gives an angle-preserving (conformal) transform to the sphere.
:

### Geocentric latitude

• The geocentric latitude, , is the angle between the equatorial plane and a line from the center of the Earth.
:

### Comparison of latitudes

The following plot shows the differences between the types of latitude. The data used is found in the table following the plot. Please note that the values in the table are in minutes, not degrees, and the plot reflects this as well. Also note that the conformal symbols are hidden behind the geocentric due to being very close in value.

Approximate difference from geographic latitude ("Lat")
Lat
Reduced
Authalic
Rectifying
Conformal
Geocentric
0.00′0.00′0.00′0.00′0.00′
1.01′1.35′1.52′2.02′2.02′
10°1.99′2.66′2.99′3.98′3.98′
15°2.91′3.89′4.37′5.82′5.82′
20°3.75′5.00′5.62′7.48′7.48′
25°4.47′5.96′6.70′8.92′8.92′
30°5.05′6.73′7.57′10.09′10.09′
35°5.48′7.31′8.22′10.95′10.96′
40°5.75′7.66′8.62′11.48′11.49′
45°5.84′7.78′8.76′11.67′11.67′
50°5.75′7.67′8.63′11.50′11.50′
55°5.49′7.32′8.23′10.97′10.98′
60°5.06′6.75′7.59′10.12′10.13′
65°4.48′5.97′6.72′8.95′8.96′
70°3.76′5.01′5.64′7.52′7.52′
75°2.92′3.90′4.39′5.85′5.85′
80°2.00′2.67′3.00′4.00′4.01′
85°1.02′1.35′1.52′2.03′2.03′
90°0.00′0.00′0.00′0.00′0.00′

### Astronomical latitude

A more obscure measure of latitude is the astronomical latitude, which is the angle between the equatorial plane and the normal to the geoid (ie a plumb line). It originated as the angle between horizon and pole star.

Astronomical latitude is not to be confused with declination, the coordinate astronomers use to describe the locations of stars north/south of the celestial equator (see equatorial coordinates), nor with ecliptic latitude, the coordinate that astronomers use to describe the locations of stars north/south of the ecliptic (see ecliptic coordinates).

### Palæolatitude

Continents move over time, due to continental drift, taking whatever fossils and other features of interest they may have with them. Particularly when discussing fossils, it's often more useful to know where the fossil was when it was laid down, than where it is when it was dug up: this is called the palæolatitude of the fossil. The Palæolatitude can be constrained by palæomagnetic data. If tiny magnetisable grains are present when the rock is being formed, these will align themselves with the Earth's magnetic field like compass needles. A magnetometer can deduce the orientation of these grains by subjecting a sample to a magnetic field, and the declination of the grains can be used to infer the latitude of deposition.

• John P. Snyder Map Projections: a working manual excerpts

## References

• Beals, K. L., Smith, C. L. & Dodd, S. M. (1984). "Brain size, cranial morphology, climate, and time machines". Current Anthropology 25: 301–330.
• Lynn, R. (1991). "The evolution of racial differences in intelligence". Mankind Quarterly 32: 99–173.

Latitude may refer to:
• Latitude, a geographical term denoting the north/south angular location of a place on a sphere
• Exposure latitude, a cinemagraphic term pertaining to over/underexposure of film
• Latitude Group, a UK search engine marketing agency

MAP may refer to:
• MAP, the ISO 639 alpha-3 for Austronesian languages
• MAP (band), an indie band from Riverside, California
• Maghreb Arab Press, the official Moroccan news agency
• Malawi Against Polio

EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001. Their greatest hit, their debut single "time after time", peaked at #13 in the Oricon singles chart.
equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. Longitude is the east-west geographic coordinate measurement most commonly utilized in cartography and global navigation.
In astronomy, geography, geometry and related sciences and contexts, a plane is said to be horizontal at a given point if it is locally perpendicular to the gradient of the gravity field, i.e., with the direction of the gravitational force (per unit mass) at that point.
equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. On the Earth, a circle of latitude is an imaginary east-west circle connecting all locations that have a given latitude.
equator is an imaginary line on the Earth's surface equidistant from the North Pole and South Pole. It thus divides the Earth into a Northern Hemisphere and a Southern Hemisphere. The equators of other planets and astronomical bodies are defined analogously.
Northern Hemisphere or northern hemisphere[1] is the half of a planet that is north of the equator—the word hemisphere literally means 'half ball'. It is also that half of the celestial sphere north of the celestial equator.
Southern Hemisphere or southern hemisphere[1] is the half of a planet that is south of the equator—the word hemisphere literally means 'half ball'. It is also that half of the celestial sphere south of the celestial equator.
Phi (uppercase Φ, lowercase φ or ϕ), pronounced [fi] in modern Greek and as [faɪ] in English, is the 21st letter of the Greek alphabet.
EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001. Their greatest hit, their debut single "time after time", peaked at #13 in the Oricon singles chart.
equator is an imaginary line on the Earth's surface equidistant from the North Pole and South Pole. It thus divides the Earth into a Northern Hemisphere and a Southern Hemisphere. The equators of other planets and astronomical bodies are defined analogously.
angle (in full, plane angle) is the figure formed by two rays sharing a common endpoint, called the vertex of the angle. The magnitude of the angle is the "amount of rotation" that separates the two rays, and can be measured by considering the length of circular arc swept
degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of plane angle, representing 1360 of a full rotation.
North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets the Earth's surface.
South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the southernmost point on the surface of the Earth. It lies on the continent of Antarctica, on the opposite side of the Earth from the North Pole.
complementary if the sum of their measures add up to 90 degrees.

If the two complementary angles are adjacent (i.e. have a common vertex and share a side, but do not have any interior points in common) their non-shared sides form a right angle.
In spherical coordinates, colatitude is the complementary angle of the latitude, i.e. the difference between the latitude and 90°.

## Astronomical use

The colatitude is useful in astronomy because it refers to the zenith distance of the celestial poles.
equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. On the Earth, a circle of latitude is an imaginary east-west circle connecting all locations that have a given latitude.
equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. On the Earth, a circle of latitude is an imaginary east-west circle connecting all locations that have a given latitude.
In geometry, a set of points in space is coplanar if the points all lie in the same geometric plane. For example, three points are always coplanar; but four points in space are usually not coplanar.
plane is a two-dimensional manifold or surface that is perfectly flat. Informally it can be thought of as an infinitely vast and infinitesimally thin sheet oriented in some space.
Parallel is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The existence and properties of parallel lines are the basis of Euclid's parallel postulate.
equator is an imaginary line on the Earth's surface equidistant from the North Pole and South Pole. It thus divides the Earth into a Northern Hemisphere and a Southern Hemisphere. The equators of other planets and astronomical bodies are defined analogously.
A small circle of a sphere is the circle constructed by a plane crossing the sphere not in its center. Small circles always have smaller diameters than the sphere itself (compare great circle).
In mathematics, a geodesic is a generalization of the notion of a "straight line" to "curved spaces". In presence of a metric, geodesics are defined to be (locally) the shortest path between points on the space.