//
// C++ Interface: earth_geometry
//
// Description: set of constants that defines the geometry of the earth
//
//
// Author: Nicolas PASCAL <nicolas.pascal@icare.univ-lille1.fr>, (C) 2012
//
// Copyright: See COPYING file that comes with this distribution
//
//

#include "earth_geometry.h"

double Earth::get_radius() {
//     if (isnan(lat))
    return Earth::authalic_radius;
//     else {
//         // compute distance from center at the surface of an ellipsoid : http://en.wikipedia.org/wiki/Earth_radius#Radius_at_a_given_geodetic_latitude
//         double lat_rad = radians(lat);
//         double cos_lat = cos (lat_rad);
//         double cos_2_lat = cos_lat * cos_lat;
//         double sin_lat = sin (lat_rad);
//         double sin_2_lat = sin_lat * sin_lat;
//         double d1 = (Earth::WGS84::a4 * cos_2_lat) + (Earth::WGS84::b4 * sin_2_lat);
//         double d2 = (Earth::WGS84::a2 * cos_2_lat) + (Earth::WGS84::b2 * sin_2_lat);
//         return sqrt (d1 / d2);
//     }
}

double Earth::WGS84::get_N(double lat) {
    double p = sin(lat);
    double w = sqrt(1 - e2*p*p);
    return a/w;
}