Editing Latitude (section)

===Geodetic and geocentric latitudes===
{{see also|Geodetic coordinates#Geodetic vs. geocentric coordinates}}

[[File:latitude and longitude graticule on an ellipsoid.svg|thumb|upright=0.9|right|The definition of geodetic latitude (<math>\phi</math>) and longitude (<math>\lambda</math>) on an ellipsoid. The normal to the surface does not pass through the centre, except at the equator and at the poles.]]

The graticule on the ellipsoid is constructed in exactly the same way as on the sphere. The normal at a point on the surface of an ellipsoid does not pass through the centre, except for points on the equator or at the poles, but the definition of latitude remains unchanged as the angle between the normal and the equatorial plane. The terminology for latitude must be made more precise by distinguishing:

*{{anchor|Geodetic}}''[[Geodetic latitude]]'': the angle between the normal and the equatorial plane. The standard notation in English publications is {{mvar|ϕ}}. This is the definition assumed when the word latitude is used without qualification. The definition must be accompanied with a specification of the ellipsoid.
*{{anchor|Geocentric}}''[[Geocentric latitude]]'' (also known as ''spherical latitude'', after the [[3D polar angle]]): the angle between the radius (from centre to the point on the surface) and the equatorial plane. (Figure [[#Geocentric latitude|below]]). There is no standard notation: examples from various texts include {{mvar|θ}}, {{mvar|ψ}}, {{mvar|q}}, {{mvar|ϕ′}}, {{math|''ϕ''<sub>c</sub>}}, {{math|''ϕ''<sub>g</sub>}}. This article uses {{mvar|θ}}.

'''Geographic latitude''' must be used with care, as some authors use it as a synonym for geodetic latitude whilst others use it as an alternative to the [[#Astronomical latitude|astronomical latitude]].
"Latitude" (unqualified) should normally refer to the geodetic latitude.

The importance of specifying the reference datum may be illustrated by a simple example. On the reference ellipsoid for WGS84, the centre of the [[Eiffel Tower]] has a geodetic latitude of 48°&nbsp;51′&nbsp;29″&nbsp;N, or 48.8583°&nbsp;N and longitude of 2°&nbsp;17′&nbsp;40″&nbsp;E or 2.2944°E. The same coordinates on the datum [[ED50]] define a point on the ground which is {{convert|140|m|ft|abbr=off}} distant from the tower.{{citation needed|date=December 2011}} A web search may produce several different values for the latitude of the tower; the reference ellipsoid is rarely specified.