Editing Latitude (section)

===The graticule on the sphere===
The graticule is formed by the lines of constant latitude and constant longitude, which are constructed with reference to the rotation axis of the Earth. The primary reference points are the [[Geographical pole|poles]] where the axis of rotation of the Earth intersects the reference surface. Planes which contain the rotation axis intersect the surface at the [[Meridian (geography)|meridians]]; and the angle between any one meridian plane and that through Greenwich (the [[Prime Meridian]]) defines the longitude: meridians are lines of constant longitude. The plane through the centre of the Earth and perpendicular to the rotation axis intersects the surface at a great circle called the [[Equator]]. Planes parallel to the equatorial plane intersect the surface in circles of constant latitude; these are the parallels. The Equator has a latitude of 0°, the [[North Pole]] has a latitude of 90° North (written 90°&nbsp;N or +90°), and the [[South Pole]] has a latitude of 90° South (written 90°&nbsp;S or −90°). The latitude of an arbitrary point is the angle between the equatorial plane and the normal to the surface at that point: the normal to the surface of the sphere is along the radial vector.

The latitude, as defined in this way for the sphere, is often termed the spherical latitude, to avoid ambiguity with the geodetic latitude and the auxiliary latitudes defined in subsequent sections of this article.