A detailed coordinate system of the Earth's latitude

First, the Earth model

The earth is an approximate ellipsoid, which is approximated by an ellipsoid model such as:

The equator is an approximate circle with a radius of a, and any circle meridian is an approximate circle with a radius of B. A is called the long axis radius of the ellipsoid, and B is called the short axis radius of the ellipsoid.

a ≈ 6378.137 km, b≈6356.752 km. (In fact, a is not constant, the most strengths and shortcomings of 72 meters, B of the most strengths and shortcomings of 42 meters, is very small)

A detailed coordinate system of the Earth's latitude