// ellipsoid
LP e_inverse(XY xy)
{
LP lp;
lp.lam = lp.phi = 0;
xy.x /= k0;
xy.y /= k0;
double rho = Libc.hypot(xy.x, xy.y);
if (rho != 0)
{
double c = 2.0 * Math.Atan2(rho, R2);
double sinc = Math.Sin(c);
double cosc = Math.Cos(c);
lp.phi = Math.Asin(cosc * sinc0 + xy.y * sinc * cosc0 / rho);
lp.lam = Math.Atan2(xy.x * sinc, rho * cosc0 * cosc - xy.y * sinc0 * sinc);
}
else
{
lp.phi = phic0;
lp.lam = 0.0;
}
return(GAUSS.pj_inv_gauss(ctx, lp, en));
}
// ellipsoid
XY e_forward(LP lp)
{
XY xy;
xy.x = xy.y = 0;
lp = GAUSS.pj_gauss(ctx, lp, en);
double sinc = Math.Sin(lp.phi);
double cosc = Math.Cos(lp.phi);
double cosl = Math.Cos(lp.lam);
double k = k0 * R2 / (1.0 + sinc0 * sinc + cosc0 * cosc * cosl);
xy.x = k * cosc * Math.Sin(lp.lam);
xy.y = k * (cosc0 * sinc - sinc0 * cosc * cosl);
return(xy);
}
public override PJ Init()
{
double R;
en = GAUSS.pj_gauss_ini(e, phi0, out phic0, out R);
if (en == null)
{
return(null);
}
sinc0 = Math.Sin(phic0);
cosc0 = Math.Cos(phic0);
R2 = 2.0 * R;
inv = e_inverse;
fwd = e_forward;
return(this);
}
