z_to_latitude()

double z_to_latitude	(	double	z,
		int	top
	)

Used in great circle to compute the pole of the great circle.

Definition at line 1045 of file lwgeodetic.c.

References FP_IS_ZERO, LWDEBUGF, and SIGNUM.

Referenced by clairaut_cartesian(), and clairaut_geographic().

{
        double sign = SIGNUM(z);
        double tlat = acos(z);
        LWDEBUGF(4, "inputs: z(%.8g) sign(%.8g) tlat(%.8g)", z, sign, tlat);
        if (FP_IS_ZERO(z))
        {
                if (top) return M_PI_2;
                else return -1.0 * M_PI_2;
        }
        if (fabs(tlat) > M_PI_2 )
        {
                tlat = sign * (M_PI - fabs(tlat));
        }
        else
        {
                tlat = sign * tlat;
        }
        LWDEBUGF(4, "output: tlat(%.8g)", tlat);
        return tlat;
}

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