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# gd2gc

erfa.gd2gc(n, elong, phi, height)

  Transform geodetic coordinates to geocentric using the specified reference ellipsoid.

  Parameters:
    n int array
    elong double array
    phi double array
    height double array
  Returns:
    xyz double array

  Notes

  Wraps ERFA function `eraGd2gc`. The ERFA documentation is:

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

      Transform geodetic coordinates to geocentric using the specified
      reference ellipsoid.

      Given:
         n       int        ellipsoid identifier (Note 1)
         elong   double     longitude (radians, east +ve, Note 3)
         phi     double     latitude (geodetic, radians, Note 3)
         height  double     height above ellipsoid (geodetic, Notes 2,3)

      Returned:
         xyz     double[3]  geocentric vector (Note 2)

      Returned (function value):
                 int        status:  0 = OK
                                    -1 = illegal identifier (Note 3)
                                    -2 = illegal case (Note 3)

      Notes:

      1) The identifier n is a number that specifies the choice of
         reference ellipsoid.  The following are supported:

            n    ellipsoid

            1     ERFA_WGS84
            2     ERFA_GRS80
            3     ERFA_WGS72

         The n value has no significance outside the ERFA software.  For
         convenience, symbols ERFA_WGS84 etc. are defined in erfam.h.

      2) The height (height, given) and the geocentric vector (xyz,
         returned) are in meters.

      3) No validation is performed on the arguments elong, phi and
         height.  An error status -1 means that the identifier n is
         illegal.  An error status -2 protects against cases that would
         lead to arithmetic exceptions.  In all error cases, xyz is set
         to zeros.

      4) The inverse transformation is performed in the function eraGc2gd.

      Called:
         eraEform     Earth reference ellipsoids
         eraGd2gce    geodetic to geocentric transformation, general
         eraZp        zero p-vector

      This revision:  2023 March 9

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