Convert geodetic position to geocentric. (double precision)
p double latitude (geodetic, radians) h double height above reference spheroid (geodetic, metres)
*r double distance from Earth axis (AU) *z double distance from plane of Earth equator (AU)
1) Geocentric latitude can be obtained by evaluating atan2(z,r). 2) IAU 1976 constants are used.
Green,R.M., Spherical Astronomy, CUP 1985, p98. P.T.Wallace Starlink 25 July 1993