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Abstract
I/O
Examples
Particulars
Required Reading
Version
Index_Entries

Abstract


   CSPICE_CGV2EL forms a SPICE ellipse from a center vector and two generating
   vectors.

I/O


   Given:

      center   the location for an ellipse center.

               [3,1] = size(center); double = class(center)

      vec1 &
      vec2     the two vectors defining the ellipse (the generating vectors)
               with the 'center' in three-dimensional space. The ellipse is
               the set of points

                  center  +  cos(theta) vec1  +  sin(theta) vec2

               where theta ranges over the interval (-pi, pi].

               'vec1' and 'vec2' need not be linearly independent.

               [3,1] = size(vec1); double = class(vec1)

               [3,1] = size(vec2); double = class(vec2)

   the call:

      ellipse = cspice_cgv2el( center, vec1, vec2 )

   returns:

      ellipse   a structure describing a SPICE ellipse defined by the input
                vectors. 

                [1,1] = size(ellipse); struct = class(ellipse)

                The structure has the fields:

                center:    [3,1] = size(center); double = class(center)
                semiMinor: [3,1] = size(semiMinor); double = class(semiMinor)
                semiMajor: [3,1] = size(semiMajor); double = class(semiMajor)

Examples


   Any numerical results shown for this example may differ between
   platforms as the results depend on the SPICE kernels used as input
   and the machine specific arithmetic implementation.

      %
      % Define the center and two linearly independent
      % generating vectors of an ellipse (the vectors need not
      % be linearly independent).
      %
      center = [ -1.;  1.; -1. ];
      vec1   = [  1.;  1.;  1. ];
      vec2   = [  1.; -1.;  1. ];

      %
      % Create the CSPICE_ELLIPSE structure.
      %
      ellipse = cspice_cgv2el( center, vec1, vec2 );

      ellipse.semiMinor
      ellipse.semiMajor
      ellipse.center

   MATLAB outputs for ellipse.semiMinor:

         ans =

             0.0000
             1.4142
             0.0000

   MATLAB outputs for ellipse.semiMajor:

         ans =

             1.4142
            -0.0000
             1.4142

   MATLAB outputs for ellipse.center:

         ans =

             -1
              1
             -1

Particulars


   SPICE ellipses serve to simplify calling sequences and reduce
   the chance for error in declaring and describing argument lists
   involving ellipses.

   The set of ellipse conversion routines is

      cspice_cgv2el( Center and generating vectors to ellipse )
      cspice_el2cgv( Ellipse to center and generating vectors )

Required Reading


   For important details concerning this module's function, please refer to
   the CSPICE routine cgv2el_c.

   MICE.REQ
   ELLIPSES.REQ

Version


   -Mice Version 1.0.1, 09-NOV-2012, EDW (JPL)

      Edited I/O section to conform to NAIF standard for Mice documentation.

   -Mice Version 1.0.0, 30-DEC-2008, EDW (JPL)

Index_Entries


   center and generating vectors to ellipse


Wed Apr  5 18:00:30 2017