Discuss with respect to celestial navigation geographical and geocentric latitudes

Of course. This is an excellent topic, as it gets to the heart of how we model our planet for navigation. The distinction between geographical and geocentric latitude arises directly from the fact that the Earth is not a perfect sphere, but an oblate spheroid—it bulges at the equator and is flattened at the poles.

Let’s discuss both with respect to celestial navigation.

1. Geographical (or Geodetic) Latitude (Φ)

This is the latitude we use on all our charts, maps, and for everyday navigation.

• Definition: Geographical latitude is the angle between the plane of the equator and a line that is perpendicular (normal) to the surface of the reference ellipsoid at a given point.

• The Concept of “Normal”: Imagine you are standing on the Earth’s surface. The direction that a plumb bob (a weight on a string) hangs points straight down towards the center of gravity. This line is your local vertical. The point directly over your head on the celestial sphere is your zenith. The geographical latitude is the angle that this local vertical line makes with the equatorial plane.

• Visualizing It: