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# gc2gde

erfa.gc2gde(a, f, xyz)

  Transform geocentric coordinates to geodetic for a reference ellipsoid of specified form.

  Parameters:
    a double array
    f double array
    xyz double array
  Returns:
    elong double array
    phi double array
    height double array

  Notes

  Wraps ERFA function `eraGc2gde`. The ERFA documentation is:

      - - - - - - - - - -
       e r a G c 2 g d e
      - - - - - - - - - -

      Transform geocentric coordinates to geodetic for a reference
      ellipsoid of specified form.

      Given:
         a       double     equatorial radius (Notes 2,4)
         f       double     flattening (Note 3)
         xyz     double[3]  geocentric vector (Note 4)

      Returned:
         elong   double     longitude (radians, east +ve)
         phi     double     latitude (geodetic, radians)
         height  double     height above ellipsoid (geodetic, Note 4)

      Returned (function value):
                 int        status:  0 = OK
                                    -1 = illegal f
                                    -2 = illegal a

      Notes:

      1) This function is based on the GCONV2H Fortran subroutine by
         Toshio Fukushima (see reference).

      2) The equatorial radius, a, can be in any units, but meters is
         the conventional choice.

      3) The flattening, f, is (for the Earth) a value around 0.00335,
         i.e. around 1/298.

      4) The equatorial radius, a, and the geocentric vector, xyz,
         must be given in the same units, and determine the units of
         the returned height, height.

      5) If an error occurs (status < 0), elong, phi and height are
         unchanged.

      6) The inverse transformation is performed in the function
         eraGd2gce.

      7) The transformation for a standard ellipsoid (such as ERFA_WGS84) can
         more conveniently be performed by calling eraGc2gd, which uses a
         numerical code to identify the required A and F values.

      Reference:

         Fukushima, T., "Transformation from Cartesian to geodetic
         coordinates accelerated by Halley's method", J.Geodesy (2006)
         79: 689-693

      This revision:  2021 May 11

      Copyright (C) 2013-2023, NumFOCUS Foundation.
      Derived, with permission, from the SOFA library.  See notes at end of file.