Index of Functions: A B C D E F G H I J K L M N O P Q R S T U V W X
Index Page sphrec_c
Table of contents
Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries
#### Procedure
       sphrec_c ( Spherical to rectangular coordinates )

       void sphrec_c ( SpiceDouble    r,
                       SpiceDouble    colat,
                       SpiceDouble    slon,
                       SpiceDouble    rectan[3] )
#### Abstract
       Convert from spherical coordinates to rectangular coordinates.
#### Required_Reading
       None.
#### Keywords
       CONVERSION
       COORDINATES
#### Brief_I/O
       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       r          I   Distance of a point from the origin.
       colat      I   Angle of the point from the Z-axis in radians.
       slon       I   Angle of the point from the XZ plane in radians.
       rectan     O   Rectangular coordinates of the point.
#### Detailed_Input
       r           is the distance of the point from the origin.

       colat       is the angle between the point and the positive z-axis in
                   radians.

       slon        is the angle of the projection of the point to the XY plane
                   from the positive X-axis in radians. The positive Y-axis is
                   at longitude PI/2 radians.
#### Detailed_Output
       rectan      are the rectangular coordinates of a point.
#### Parameters
       None.
#### Exceptions
       Error free.
#### Files
       None.
#### Particulars
       This routine returns the rectangular coordinates of a point
       whose position is input in spherical coordinates.

       Spherical coordinates are defined by a distance from a central
       reference point, an angle from a reference meridian, and an angle
       from the z-axis. The co-latitude of the positive Z-axis is
       zero. The longitude of the posive Y-axis is PI/2 radians.
#### Examples
       The numerical results shown for these examples may differ across
       platforms. The results depend on the SPICE kernels used as
       input, the compiler and supporting libraries, and the machine
       specific arithmetic implementation.

       1) Compute the spherical coordinates of the position of the Moon
          as seen from the Earth, and convert them to rectangular
          coordinates.

          Use the meta-kernel shown below to load the required SPICE
          kernels.

             KPL/MK

             File name: sphrec_ex1.tm

             This meta-kernel is intended to support operation of SPICE
             example programs. The kernels shown here should not be
             assumed to contain adequate or correct versions of data
             required by SPICE-based user applications.

             In order for an application to use this meta-kernel, the
             kernels referenced here must be present in the user's
             current working directory.

             The names and contents of the kernels referenced
             by this meta-kernel are as follows:

                File name                     Contents
                ---------                     --------
                de421.bsp                     Planetary ephemeris
                naif0012.tls                  Leapseconds

             \begindata

                KERNELS_TO_LOAD = ( 'de421.bsp',
                                    'naif0012.tls'  )

             \begintext

             End of meta-kernel

          Example code begins here.

          /.
             Program sphrec_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

                SpiceDouble          colat;
             SpiceDouble          et;
             SpiceDouble          lt;
             SpiceDouble          pos    [3];
             SpiceDouble          radius;
             SpiceDouble          rectan [3];
             SpiceDouble          slon;

             /.
             Load SPK and LSK kernels, use a meta kernel for
             convenience.
             ./
             furnsh_c ( "sphrec_ex1.tm" );

             /.
             Look up the geometric state of the Moon as seen from
             the Earth at 2017 Mar 20, relative to the J2000
             reference frame.
             ./
             str2et_c ( "2017 Mar 20", &et );

             spkpos_c ( "Moon", et, "J2000", "NONE", "Earth", pos, &lt );

             /.
             Convert the position vector `pos' to spherical
             coordinates.
             ./
             recsph_c ( pos, &radius, &colat, &slon );

             /.
             Convert the spherical coordinates to rectangular.
             ./
             sphrec_c ( radius, colat, slon, rectan );

             printf( " \n" );
             printf( "Original rectangular coordinates:\n" );
             printf( " \n" );
             printf( " X           (km):  %19.8f\n", pos[0] );
             printf( " Y           (km):  %19.8f\n", pos[1] );
             printf( " Z           (km):  %19.8f\n", pos[2] );
             printf( " \n" );
             printf( "Spherical coordinates:\n" );
             printf( " \n" );
             printf( " Radius      (km):  %19.8f\n", radius );
             printf( " Colatitude (deg):  %19.8f\n", colat*dpr_c ( ) );
             printf( " Longitude  (deg):  %19.8f\n", slon*dpr_c ( ) );
             printf( " \n" );
             printf( "Rectangular coordinates from sphrec_c:\n" );
             printf( " \n" );
             printf( " X           (km):  %19.8f\n", rectan[0] );
             printf( " Y           (km):  %19.8f\n", rectan[1] );
             printf( " Z           (km):  %19.8f\n", rectan[2] );
             printf( " \n" );

             return ( 0 );
          }

          When this program was executed on a Mac/Intel/cc/64-bit
          platform, the output was:

          Original rectangular coordinates:

           X           (km):      -55658.44323296
           Y           (km):     -379226.32931475
           Z           (km):     -126505.93063865

          Spherical coordinates:

           Radius      (km):      403626.33912495
           Colatitude (deg):         108.26566077
           Longitude  (deg):         -98.34959789

          Rectangular coordinates from sphrec_c:

           X           (km):      -55658.44323296
           Y           (km):     -379226.32931475
           Z           (km):     -126505.93063865

       2) Create a table showing a variety of spherical coordinates
          and the corresponding rectangular coordinates.

          Corresponding spherical and rectangular coordinates are
          listed to three decimal places. Input angles are in degrees.

          Example code begins here.

          /.
             Program sphrec_ex2
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define NREC         11

             /.
             Local variables.
             ./
             SpiceDouble          rcolat;
             SpiceDouble          rslon;
             SpiceDouble          rectan [3];

             SpiceInt             i;

             /.
             Define the input spherical coordinates. Angles in degrees.
             ./
             SpiceDouble          radius [NREC] = {  0.0,  1.0,     1.0,
                                                     1.0,  1.0,     1.0,
                                                     1.0,  1.4142,  1.4142,
                                                  1.4142,  1.7320          };

             SpiceDouble          colat  [NREC] = {  0.0,  90.0,  90.0,
                                                     0.0,  90.0,  90.0,
                                                   180.0,  90.0,  45.0,
                                                    45.0,  54.7356     };

             SpiceDouble          slon   [NREC] = {  0.0,   0.0,  90.0,
                                                     0.0, 180.0, -90.0,
                                                     0.0,  45.0,   0.0,
                                                    90.0,  45.0        };

             /.
             Print the banner.
             ./
             printf( "  radius   colat     slon   rect[0]  rect[1]  rect[2]\n" );
             printf( " -------  -------  -------  -------  -------  -------\n" );

             /.
             Do the conversion.
             ./
             for ( i = 0; i < NREC; i++ )
             {

                rcolat = colat[i] * rpd_c ( );
                rslon  = slon[i]  * rpd_c ( );

                sphrec_c ( radius[i], rcolat, rslon, rectan );

                printf( "%8.3f %8.3f %8.3f ",  radius[i], colat[i],  slon[i]   );
                printf( "%8.3f %8.3f %8.3f\n", rectan[0], rectan[1], rectan[2] );

             }

             return ( 0 );
          }

          When this program was executed on a Mac/Intel/cc/64-bit
          platform, the output was:

            radius   colat     slon   rect[0]  rect[1]  rect[2]
           -------  -------  -------  -------  -------  -------
             0.000    0.000    0.000    0.000    0.000    0.000
             1.000   90.000    0.000    1.000    0.000    0.000
             1.000   90.000   90.000    0.000    1.000    0.000
             1.000    0.000    0.000    0.000    0.000    1.000
             1.000   90.000  180.000   -1.000    0.000    0.000
             1.000   90.000  -90.000    0.000   -1.000    0.000
             1.000  180.000    0.000    0.000    0.000   -1.000
             1.414   90.000   45.000    1.000    1.000    0.000
             1.414   45.000    0.000    1.000    0.000    1.000
             1.414   45.000   90.000    0.000    1.000    1.000
             1.732   54.736   45.000    1.000    1.000    1.000
#### Restrictions
       None.
#### Literature_References
       None.
#### Author_and_Institution
       J. Diaz del Rio     (ODC Space)
       B.V. Semenov        (JPL)
       W.L. Taber          (JPL)
       E.D. Wright         (JPL)
#### Version
       -CSPICE Version 1.1.0, 05-JUL-2021 (JDR)

           Changed the output argument name "lon" to "slon" for
           consistency with other routines.

           Edited the header to comply with NAIF standard.
           Added complete code examples.

       -CSPICE Version 1.0.1, 26-JUL-2016 (BVS)

           Minor headers edits.

       -CSPICE Version 1.0.0, 08-FEB-1998 (EDW) (WLT)
#### Index_Entries
       spherical to rectangular coordinates
#### Link to routine sphrec_c source file sphrec_c.c

    Fri Dec 31 18:41:12 2021