// elliptical
LP e_inverse(XY xy)
{
LP lp;
lp.lam = lp.phi = 0;
double c = Libc.hypot(xy.x, xy.y);
if (c < EPS10)
{
lp.phi = phi0;
lp.lam = 0.0;
return(lp);
}
if (mode == aeqd_mode.OBLIQ || mode == aeqd_mode.EQUIT)
{
double x2 = xy.x * a;
double y2 = xy.y * a;
double lat1 = phi0 * RHO;
double lon1 = lam0 * RHO;
double azi1 = Math.Atan2(x2, y2) * RHO;
double s12 = Math.Sqrt(x2 * x2 + y2 * y2);
double lat2, lon2, azi2;
g.geod_direct(lat1, lon1, azi1, s12, out lat2, out lon2, out azi2);
lp.phi = lat2 / RHO;
lp.lam = lon2 / RHO;
lp.lam -= lam0;
}
else
{ // Polar
lp.phi = Proj.pj_inv_mlfn(ctx, mode == aeqd_mode.N_POLE?Mp - c:Mp + c, es, en);
lp.lam = Math.Atan2(xy.x, mode == aeqd_mode.N_POLE?-xy.y:xy.y);
}
return(lp);
}
