int eraGc2gde	(	double	a,
		double	f,
		double	xyz[3],
		double *	elong,
		double *	phi,
		double *	height
	)

Definition at line 3 of file gc2gde.c.

References ERFA_DPI.

Referenced by eraGc2gd(), and t_gc2gde().

{
   double aeps2, e2, e4t, ec2, ec, b, x, y, z, p2, absz, p, s0, pn, zc,
                 c0, c02, c03, s02, s03, a02, a0, a03, d0, f0, b0, s1,
                 cc, s12, cc2;


/* ------------- */
/* Preliminaries */
/* ------------- */

/* Validate ellipsoid parameters. */
   if ( f < 0.0 || f >= 1.0 ) return -1;
   if ( a <= 0.0 ) return -2;

/* Functions of ellipsoid parameters (with further validation of f). */
   aeps2 = a*a * 1e-32;
   e2 = (2.0 - f) * f;
   e4t = e2*e2 * 1.5;
   ec2 = 1.0 - e2;
   if ( ec2 <= 0.0 ) return -1;
   ec = sqrt(ec2);
   b = a * ec;

/* Cartesian components. */
   x = xyz[0];
   y = xyz[1];
   z = xyz[2];

/* Distance from polar axis squared. */
   p2 = x*x + y*y;

/* Longitude. */
   *elong = p2 > 0.0 ? atan2(y, x) : 0.0;

/* Unsigned z-coordinate. */
   absz = fabs(z);

/* Proceed unless polar case. */
   if ( p2 > aeps2 ) {

   /* Distance from polar axis. */
      p = sqrt(p2);

   /* Normalization. */
      s0 = absz / a;
      pn = p / a;
      zc = ec * s0;

   /* Prepare Newton correction factors. */
      c0 = ec * pn;
      c02 = c0 * c0;
      c03 = c02 * c0;
      s02 = s0 * s0;
      s03 = s02 * s0;
      a02 = c02 + s02;
      a0 = sqrt(a02);
      a03 = a02 * a0;
      d0 = zc*a03 + e2*s03;
      f0 = pn*a03 - e2*c03;

   /* Prepare Halley correction factor. */
      b0 = e4t * s02 * c02 * pn * (a0 - ec);
      s1 = d0*f0 - b0*s0;
      cc = ec * (f0*f0 - b0*c0);

   /* Evaluate latitude and height. */
      *phi = atan(s1/cc);
      s12 = s1 * s1;
      cc2 = cc * cc;
      *height = (p*cc + absz*s1 - a * sqrt(ec2*s12 + cc2)) /
                                                        sqrt(s12 + cc2);
   } else {

   /* Exception: pole. */
      *phi = ERFA_DPI / 2.0;
      *height = absz - b;
   }

/* Restore sign of latitude. */
   if ( z < 0 ) *phi = -*phi;

/* OK status. */
   return 0;

}

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