Spherical Geometry #3 - Latitudes

The latitudes of the Earth are small circles except the Equator. We consider the Earth to be a perfect sphere for simplicity. We define the latitude (Φ) of a point as the angle which between the point, the centre of the sphere, and the corresponding point in the great circle directly below it. In the diagram shown, the latitude of a point B is the angle BOD.

Latitude is measured in degrees, arc minutes and arc seconds north or south from the Equator. It is obvious that the latitude of the Equator is 0° and that of the North/South pole is 90° N/S.

 Another useful term related to latitude is the colatitude. The colatitude is angle from the pole to the centre to the point. In other words, colatitude is the complementary angle of the latitude. In the diagram the colatitude of B is the angle POB. So POB = 90° - DOB. 

Hope that was useful...

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