pub fn phi2(ts0: f64, e: f64) -> f64Expand description
Determine latitude angle phi-2. Inputs: ts = exp(-psi) where psi is the isometric latitude (dimensionless) this variable is defined in Snyder (1987), Eq. (7-10) e = eccentricity of the ellipsoid (dimensionless) Output: phi = geographic latitude (radians) Here isometric latitude is defined by psi = log( tan(pi/4 + phi/2) * ( (1 - esin(phi)) / (1 + esin(phi)) )^(e/2) ) = asinh(tan(phi)) - e * atanh(e * sin(phi)) = asinh(tan(chi)) chi = conformal latitude
This routine converts t = exp(-psi) to
tau’ = tan(chi) = sinh(psi) = (1/t - t)/2
returns atan(sinpsi2tanphi(tau’))