CONVERT

        [GREG2\]CONVERT  A0  D0  [Angle] [/TYPE Ptype] [/UNIT Unit] [/SYSTEM
    EQU|GAL [Equinox]] [/VARIABLE Var_X Var_Y]

    The command converts coordinates in a given  projection  and  coordinate
    system to GREG current ones:

      * Input:
        - Coordinates  are  found in Var_X and Var_Y if the option /VARIABLE
          is present, else buffers X and Y are used. Var_X and Var_Y must be
          DOUBLE  precision,  writeable, 1-dimensional arrays. If input pro-
          jection type is NONE, values are absolute  spherical  coordinates.
          Else they are offsets from the projection center.
        - The  unit of coordinates can be set with the option /UNIT with the
          argument SECOND, MINUTE, DEGREE, or  RADIAN.  Default  is  current
          Greg angle unit (see HELP G\SET ANGLE_UNIT).
        - Input  coordinate  system  is  set with the option /SYSTEM EQU|GAL
          [Equinox]. Default equinox is 2000 if system is Equatorial.
        - Input projection is  defined  by  CONVERT  A0  D0  [Angle]  [/TYPE
          Ptype].  A0  and  D0  are the coordinates of the projection center
          (reference of the offset coordinates). They  are  relevant  except
          for  the NONE projection. Format is degrees in sexagesimal strings
          (A0 is hour angle if input system is EQUATORIAL). Angle, if  rele-
          vant,  must  be  set in degrees. Supported types can be found with
          CONVERT /TYPE ?. Default is NONE.

      * Output:
        - Converted coordinates are saved in the input variables  (overwrit-
          ten).  If the current Greg projection is NONE, values are absolute
          spherical coordinates. Else they are offsets from the current Greg
          projection center.
        - The  unit  of output coordinates is always natural units (i.e. the
          equivalent of Radians after reprojection).
        - Output coordinate system is the current Greg one (see SHOW  SYSTEM
          and HELP SET SYSTEM).
        - Output  projection  (center and type) is the current Greg one (see
          HELP PROJECTION).

    There is no provision for "hidden" parts which are  treated  exactly  as
    visible ones.