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# gd2gce

erfa.gd2gce(a, f, elong, phi, height)

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

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

  Notes

  Wraps ERFA function `eraGd2gce`. The ERFA documentation is:

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

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

      Given:
         a       double     equatorial radius (Notes 1,4)
         f       double     flattening (Notes 2,4)
         elong   double     longitude (radians, east +ve)
         phi     double     latitude (geodetic, radians, Note 4)
         height  double     height above ellipsoid (geodetic, Notes 3,4)

      Returned:
         xyz     double[3]  geocentric vector (Note 3)

      Returned (function value):
                 int        status:  0 = OK
                                    -1 = illegal case (Note 4)
      Notes:

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

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

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

      4) No validation is performed on individual arguments.  The error
         status -1 protects against (unrealistic) cases that would lead
         to arithmetic exceptions.  If an error occurs, xyz is unchanged.

      5) The inverse transformation is performed in the function
         eraGc2gde.

      6) The transformation for a standard ellipsoid (such as ERFA_WGS84) can
         more conveniently be performed by calling eraGd2gc,  which uses a
         numerical code to identify the required a and f values.

      References:

         Green, R.M., Spherical Astronomy, Cambridge University Press,
         (1985) Section 4.5, p96.

         Explanatory Supplement to the Astronomical Almanac,
         P. Kenneth Seidelmann (ed), University Science Books (1992),
         Section 4.22, p202.

      This revision:  2021 May 11

      Copyright (C) 2013-2021, NumFOCUS Foundation.
      Derived, with permission, from the SOFA library.  See notes at end of file.