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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).

- 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

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°.

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 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.

- $$

- $begin\{align\}$

M(phi)&=acdotcos^2(o!varepsilon)n'(phi)^3=frac{(ab)^2}{Big(a^2cos^2(phi)+b^2sin^2(phi)Big)^{3/2}}; N(phi)&=a{cdot}n'(phi) =frac{a^2}{sqrt{a^2cos^2(phi)+b^2sin^2(phi)}};end{align},!

In the case of a spheroid, a meridian and its anti-meridian form an ellipse, from which an exact expression for the length of an arcdegree of latitude difference is:

- $frac\{pi\}\{180^circ\}M(phi);!$

Similarly, an exact expression for the length of an arcdegree of longitude difference is:

- $frac\{pi\}\{180^circ\}cos(phi)N(phi);!$

Along the equator (east-west), $N;!$ equals the equatorial radius. The radius of curvature at a right angle to the equator (north-south), $M;!$, is 43 km shorter, hence the length of an arcdegree of latitude difference at the equator is about 1 km less than the length of an arcdegree of longitude difference at the equator. The radii of curvature are equal at the poles where they are about 64 km greater than the north-south equatorial radius of curvature because the polar radius is 21 km less than the equatorial radius. The shorter polar radii indicate that the northern and southern hemispheres are flatter, making their radii of curvature longer. This flattening also 'pinches' the north-south equatorial radius of curvature, making it 43 km less than the equatorial radius. Both radii of curvature are perpendicular to the plane tangent to the surface of the ellipsoid at all latitudes, directed toward a point on the polar axis in the opposite hemisphere (except at the equator where both point toward Earth's center). The east-west radius of curvature reaches the axis, whereas the north-south radius of curvature is shorter at all latitudes except the poles.

The WGS84 ellipsoid, used by all GPS devices, uses an equatorial radius of 6378137.0 m and an inverse flattening, (1/f), of 298.257223563, hence its polar radius is 6356752.3142 m and its first eccentricity squared is 0.00669437999014. The more recent but little used IERS 2003 ellipsoid provides equatorial and polar radii of 6378136.6 and 6356751.9 m, respectively, and an inverse flattening of 298.25642. Lengths of degrees on the WGS84 and IERS 2003 ellipsoids are the same when rounded to six significant digits. An appropriate calculator for any latitude is provided by the U.S. government's National Geospatial-Intelligence Agency (NGA).

Latitude | N-S radius of curvature $M;!$ | Surface distance per 1° change in latitude | E-W radius of curvature $N;!$ | Surface distance per 1° change in longitude | |
---|---|---|---|---|---|

0° | 6335.44 km | 110.574 km | 6378.14 km | 111.320 km | |

15° | 6339.70 km | 110.649 km | 6379.57 km | 107.551 km | |

30° | 6351.38 km | 110.852 km | 6383.48 km | 96.486 km | |

45° | 6367.38 km | 111.132 km | 6388.84 km | 78.847 km | |

60° | 6383.45 km | 111.412 km | 6394.21 km | 55.800 km | |

75° | 6395.26 km | 111.618 km | 6398.15 km | 28.902 km | |

90° | 6399.59 km | 111.694 km | 6399.59 km | 0.000 km |

For planets other than Earth, such as Mars, geographic and geocentric latitude are called "planetographic" and "planetocentric" latitude, respectively. Most maps of Mars since 2002 use planetocentric coordinates.

- In common usage, "latitude" refers to geodetic or geographic latitude $phi,!$ and is the angle between the equatorial plane and a line that is normal to the reference ellipsoid, which approximates the shape of Earth to account for flattening of the poles and bulging of the equator.

The expressions following assume elliptical polar sections and that all sections parallel to the equatorial plane are circular. Geographic latitude (with longitude) then provides a Gauss map.

- On a spheroid, lines of reduced or parametric latitude, $beta,!$, form circles whose radii are the same as the radii of circles formed by the corresponding lines of latitude on a sphere with radius equal to the equatorial radius of the spheroid.

- $beta=arctanBig(cos(o!varepsilon)tan(phi)Big);,!$

- Authalic latitude, $xi,!$, gives an area-preserving transform to the sphere.

- $widehat\{S\}(phi)^2=frac\{1\}\{2\}b^2left(sin(phi)n\text{'}(phi)^2+frac\{lnbigg(n\text{'}(phi)Big(1+sin(phi)sin(o!varepsilon)Big)bigg)\}\{sin(o!varepsilon)\}right);,!$

- $begin\{align\}xi\&=arcsin!left(frac\{widehat\{S\}(phi)^2\}\{widehat\{S\}(90^circ)^2\}right),$

- Rectifying latitude, $mu,!$, is the surface distance from the equator, scaled so the pole is 90°, but involves elliptic integration:

- $mu=frac\{;int\_\{0\}^phi;M(theta),dtheta\}\{frac\{2\}\{pi\}int\_\{0\}^\{90^circ\}M(phi),dphi\}$

- Conformal latitude, $chi,!$, gives an angle-preserving (conformal) transform to the sphere.

- $chi=2cdotarctanleft(sqrt\{frac\{1+sin(phi)\}\{1-sin(phi)\}cdotleft(frac\{1-sin(phi)sin(o!varepsilon)\}\{1+sin(phi)sin(o!varepsilon)\}right)^\{!!sin(o!varepsilon)\}\}^\{color\{white\};right)-frac\{pi\}\{2\};;!$

- The geocentric latitude, $psi,!$, is the angle between the equatorial plane and a line from the center of Earth.

- $psi=arctanBig(cos(o!varepsilon)^2tan(phi)Big).;!$

### 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. It differs from the geodetic latitude only slightly, due to the slight deviations of the geoid from the reference ellipsoid.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 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 magnetic declination of the grains can be used to infer the latitude of deposition.### Corrections for altitude

When converting from geodetic ("common") latitude to other types of latitude, corrections must be made for altitude for systems which do not measure the angle from the normal of the spheroid. For example, in the figure at right, point H (located on the surface of the spheroid) and point H' (located at some greater elevation) have different geocentric latitudes (angles β and γ respectively), even though they share the same geodetic latitude (angle α). Note that the flatness of the spheroid and elevation of point H' in the image is significantly greater than what is found on the Earth, exaggerating the errors inherent in such calculations if left uncorrected. Note also that the reference ellipsoid used in the geodetic system is itself just an approximation of the true geoid, and therefore introduces its own errors, though the differences are only slight (see Astronomical latitude, above).

## Further reading

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

## See also

## Footnotes

## External links

- Free GeoCoder
- GEONets Names Server, access to the National Geospatial-Intelligence Agency's (NGA) database of foreign geographic feature names.
- Look-up Latitude and Longitude
- Resources for determining your latitude and longitude
- Convert decimal degrees into degrees, minutes, seconds - Info about decimal to sexagesimal conversion
- Convert decimal degrees into degrees, minutes, seconds
- Latitude and longitude converter – Convert latitude and longitude from degree, decimal form to degree, minutes, seconds form and vice versa. Also included a farthest point and a distance calculator.
- Worldwide Index - Tageo.com – contains 2,700,000 coordinates of places including US towns
- for each city it gives the satellite map location, country, province, coordinates (dd,dms), variant names and nearby places.
- Distance calculation based on latitude and longitude - JavaScript version
- Average Latitude & Longitude of Countries
- Get the latitude and longitude of any place in the World
- Latitude / Longitude Converter – convert latitude / longitude between DMS and decimal formats.

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Last updated on Saturday October 11, 2008 at 12:48:18 PDT (GMT -0700)

View this article at Wikipedia.org - Edit this article at Wikipedia.org - Donate to the Wikimedia FoundationCopyright © 2015 Dictionary.com, LLC. All rights reserved.Approximate difference from geographic latitude ("Lat") Lat

$phi,!$Reduced

$phi-beta,!$Authalic

$phi-xi,!$Rectifying

$phi-mu,!$Conformal

$phi-chi,!$Geocentric

$phi-psi,!$0° 0.00′ 0.00′ 0.00′ 0.00′ 0.00′ 5° 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′