| pe_phi_to_beta |
Calculates the authalic latitude from the geographic latitude
double pe_phi_to_beta (double e2, double phi);
| e2 | Eccentricity squared of the spheroid |
| phi | Geographic latitude (measured in radians) of the point |
Authalic latitude maps the spheroid to an auxiliary sphere such that the sphere is equal in area to that of the spheroid.

Authalic latitude (measured in radians) of the point