Editing Spherical coordinate system (section)

=== In geography ===
{{main|Geographic coordinate system}}
{{see also|ECEF}}

Instead of inclination, the [[geographic coordinate system]] uses elevation angle (or ''[[latitude]]''), in the range (aka [[Interval (mathematics)|domain]]) {{math|−90° ≤ ''φ'' ≤ 90°}} and rotated north from the [[equator]] plane. Latitude (i.e., ''the angle'' of latitude) may be either ''[[geocentric latitude]]'', measured (rotated) from the Earth's center{{mdash}}and designated variously by {{math|''ψ'', ''q'', ''φ''′, ''φ''<sub>c</sub>, ''φ''<sub>g</sub>}}{{mdash}}or ''[[geodetic latitude]]'', measured (rotated) from the observer's [[local vertical]], and typically designated {{mvar|φ}}.
The polar angle (inclination), which is 90° minus the latitude and ranges from 0 to 180°, is called ''[[colatitude]]'' in geography.

The azimuth angle (or ''[[longitude]]'') of a given position on Earth, commonly denoted by {{mvar|λ}}, is measured in degrees east or west from some conventional reference [[meridian (geography)|meridian]] (most commonly the [[IERS Reference Meridian]]); thus its domain (or range) is {{math|−180° ≤ ''λ'' ≤ 180°}} and a given reading is typically designated "East" or "West". For positions on the [[Earth]] or other solid [[celestial body]], the reference plane is usually taken to be the plane perpendicular to the [[axis of rotation]]. <!--Must explain the conventions for positive latitude and longitude-->

Instead of the radial distance {{mvar|r}} geographers commonly use ''[[altitude]]'' above or below some local reference surface (''[[vertical datum]]''), which, for example, may be the [[mean sea level]]. When needed, the radial distance can be computed from the altitude by adding the [[radius of Earth]], which is approximately {{convert|6360|±|11|km|mi|0|abbr=in}}.

However, modern geographical coordinate systems are quite complex, and the positions implied by these simple formulae may be inaccurate by several kilometers. The precise standard meanings of ''latitude, longitude'' and ''altitude'' are currently defined by the [[World Geodetic System]] (WGS), and take into account the flattening of the Earth at the poles (about {{convert|21|km|mi|abbr=in|disp=or}}) and many other details.

[[Planetary coordinate system]]s use formulations analogous to the geographic coordinate system.