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Abstract
I/O
Examples
Particulars
Required Reading
Version
Index_Entries

Abstract


   CSPICE_SPHREC converts spherical coordinates to rectangular
   (Cartesian) coordinates.

I/O


   Given:

      r        the value(s) describing the distance of the position
               from the origin.

               [1,n] = size(r); double = class(r)

      colat    the value(s) describing the angle between the point and the
               positive z-axis, measured in radians (also referred to
               as the polar angle).

               [1,n] = size(colat); double = class(colat)

      lon      the value(s) describing the angle of the projection of the
               point to the XY plane from the positive X-axis, measured
               in radians, with range:

                   -pi < lon <= pi

               The positive Y-axis is at longitude PI/2 radians.

               [1,n] = size(lon); double = class(lon)

   the call:

       rectan = cspice_sphrec( r, colat, lon)

   returns:

      rectan   the array(s) containing the rectangular coordinates of the
               position or set of positions

               [3,n] = size(rectan); double = class(rectan)

               The argument 'rectan' returns in the same units associated
               with 'r'.

               'rectan' returns with the same vectorization measure, N,
                as 'r', 'colat', and 'lon'.

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.

   Example (1):

      %
      % Load an SPK, leapseconds, and PCK kernel set.
      %
      cspice_furnsh( 'standard.tm' )

      %
      % Create a vector of scalar times.
      %
      et = [0:2]*2.*cspice_spd;

      %
      % Retrieve the position of the moon seen from earth at 'et'
      % in the J2000 frame without aberration correction.
      %
      [pos, et] = cspice_spkpos( 'MOON', et, 'J2000', 'NONE', 'EARTH' );

      %
      % Convert the array of position vectors 'pos' to spherical
      % coordinates.
      %
      [r, colat, lon] = cspice_recsph(pos);

      %
      % Convert the spherical to rectangular.
      %
      [rectan] = cspice_sphrec(r, colat, lon);

      %
      % Calculate the relative error against the original position
      % vectors.
      %
      (rectan-pos) ./ pos

   MATLAB outputs:

      1.0e-14 *

                     0  -0.03701547067225   0.63783453323816
      0.02182376758148   0.01641520435413  -0.01531271963894
     -0.01912147275010  -0.04855217028457   0.02039513446643

      Example (2):

      %
      % Define eleven sets of spherical coordinates, 'lon' and 'colat'
      % expressed in degrees - converted to radians by use of cspice_rpd.
      %
      r     = [  0., 1., 1., 1., 1., 1., 1., ...
                 sqrt(2), sqrt(2), sqrt(2), sqrt(3) ];
      colat = [  0., 90., 90., 0., 90., 90., ...
                 180. 90., 45., 45., 54.7356] * cspice_rpd;
      lons  = [  0., 0., 90., 0., 180., -90.,...
                 0., 45., 0., 90., 45] * cspice_rpd;

      %
      % ...convert the spherical coordinates to rectangular coordinates
      %
      rec = cspice_sphrec(r, colat, lons);

      %
      % Loop over each set of coordinates for output, convert  'colat' and
      % 'lons' to degrees...
      %
      colat = colat * cspice_dpr;
      lons  = lons  * cspice_dpr;

      %
      % Output banner.
      %
      disp('     r        colat       lons         x         y           z   ')
      disp('  --------   --------   --------   --------   --------   --------')

      %
      % Create an array of values for output.
      %
      output = [ r; colat; lons; rec(1,:); rec(2,:); rec(3,:)];
      txt    = sprintf( '%10.4f %10.4f %10.4f %10.4f %10.4f %10.4f\n', output);
      disp( txt )

      %
      % It's always good form to unload kernels after use,
      % particularly in MATLAB due to data persistence.
      %
      cspice_kclear

   MATLAB outputs:

        r        colat       lons         x         y           z
     --------   --------   --------   --------   --------   --------
       0.0000     0.0000     0.0000     0.0000     0.0000     0.0000
       1.0000    90.0000     0.0000     1.0000     0.0000     0.0000
       1.0000    90.0000    90.0000     0.0000     1.0000     0.0000
       1.0000     0.0000     0.0000     0.0000     0.0000     1.0000
       1.0000    90.0000   180.0000    -1.0000     0.0000     0.0000
       1.0000    90.0000   -90.0000     0.0000    -1.0000     0.0000
       1.0000   180.0000     0.0000     0.0000     0.0000    -1.0000
       1.4142    90.0000    45.0000     1.0000     1.0000     0.0000
       1.4142    45.0000     0.0000     1.0000     0.0000     1.0000
       1.4142    45.0000    90.0000     0.0000     1.0000     1.0000
       1.7321    54.7356    45.0000     1.0000     1.0000     1.0000

Particulars


   None.

Required Reading


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

   MICE.REQ

Version


   -Mice Version 1.0.1, 01-DEC-2014, EDW (JPL)

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

   -Mice Version 1.0.0, 22-NOV-2005, EDW (JPL)

Index_Entries


   spherical to rectangular coordinates


Wed Apr  5 18:00:34 2017