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Index Page cyllat_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

       cyllat_c ( Cylindrical to latitudinal )

       void cyllat_c ( SpiceDouble    r,
                       SpiceDouble    clon,
                       SpiceDouble    z,
                       SpiceDouble *  radius,
                       SpiceDouble *  lon,
                       SpiceDouble *  lat )

#### Abstract

       Convert from cylindrical to latitudinal coordinates.

#### Required_Reading

       None.

#### Keywords

       CONVERSION
       COORDINATES

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       r          I   Distance of point from z axis.
       clon       I   Cylindrical angle of point from XZ plane (radians).
       z          I   Height of point above XY plane.
       radius     O   Distance of point from origin.
       lon        O   Longitude of point (radians).
       lat        O   Latitude of point (radians).

#### Detailed_Input

       r           is the distance of the input point from Z axis.

       clon        is the cylindrical angle of the point from XZ plane
                   (radians).

       z           is the height of the point above XY plane.

#### Detailed_Output

       radius      is the distance of the input point from origin.

       lon         is the longitude (i.e. angle from the XZ plane) of the
                   input point (radians). `lon' is set equal to `clon'.

       lat         is the latitude (i.e. angle above the XY plane) of the
                   input point (radians). The range of `lat' is [-pi, pi].

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

       This routine converts coordinates given in cylindrical
       coordinates to coordinates in latitudinal coordinates.

       Latitudinal coordinates are defined by a distance from a central
       reference point, an angle from a reference meridian, and an angle
       above the equator of a sphere centered at the central reference
       point.

#### 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 cylindrical coordinates of the position of the
          Moon as seen from the Earth, and convert them to latitudinal
          and rectangular coordinates.

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

             KPL/MK

             File name: cyllat_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 cyllat_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local variables
             ./
             SpiceDouble          clon;
             SpiceDouble          et;
             SpiceDouble          lat;
             SpiceDouble          lon;
             SpiceDouble          lt;
             SpiceDouble          pos    [3];
             SpiceDouble          radius;
             SpiceDouble          rectan [3];
             SpiceDouble          r;
             SpiceDouble          z;

             /.
             Load SPK and LSK kernels, use a meta kernel for
             convenience.
             ./
             furnsh_c ( "cyllat_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 cylindrical
             coordinates.
             ./
             reccyl_c ( pos, &r, &clon, &z );

             /.
             Convert the cylindrical coordinates to latitudinal.
             ./
             cyllat_c ( r, clon, z, &radius, &lon, &lat );

             /.
             Convert the latitudinal coordinates to rectangular.
             ./
             latrec_c ( radius, lon, lat, 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( "Cylindrical coordinates:\n" );
             printf( " \n" );
             printf( " Radius     (km):  %19.8f\n", r );
             printf( " Longitude (deg):  %19.8f\n", clon*dpr_c ( ) );
             printf( " Z          (km):  %19.8f\n", z );
             printf( " \n" );
             printf( "Latitudinal coordinates:\n" );
             printf( " \n" );
             printf( " Radius     (km):  %19.8f\n", radius );
             printf( " Longitude (deg):  %19.8f\n", lon*dpr_c ( ) );
             printf( " Latitude  (deg):  %19.8f\n", lat*dpr_c ( ) );
             printf( " \n" );
             printf( "Rectangular coordinates from latrec_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

          Cylindrical coordinates:

           Radius     (km):      383289.01777726
           Longitude (deg):         261.65040211
           Z          (km):     -126505.93063865

          Latitudinal coordinates:

           Radius     (km):      403626.33912495
           Longitude (deg):         261.65040211
           Latitude  (deg):         -18.26566077

          Rectangular coordinates from latrec_c:

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

       2) Create a table showing a variety of cylindrical coordinates
          and the corresponding latitudinal coordinates.

          Corresponding latitudinal and cylindrical coordinates are
          listed to three decimal places. All input and output angles
          are in degrees.

          Example code begins here.

          /.
             Program cyllat_ex2
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define NREC         11

             /.
             Local variables.
             ./
             SpiceDouble          lat;
             SpiceDouble          lon;
             SpiceDouble          radius;
             SpiceDouble          rclon;

             SpiceInt             i;

             /.
             Define the input cylindrical coordinates. Angles
             in degrees.
             ./

             SpiceDouble          r      [NREC] = { 0.0, 1.0, 1.0,
                                                    0.0, 1.0, 1.0,
                                                    0.0, 1.0, 1.0,
                                                    0.0, 0.0      };

             SpiceDouble          clon   [NREC] = {   0.0,   0.0,  90.0,
                                                      0.0, 180.0, -90.0,
                                                      0.0,  45.0, 180.0,
                                                    180.0,  33.0        };

             SpiceDouble          z      [NREC] = {  0.0,  0.0,  0.0,
                                                     1.0,  1.0,  0.0,
                                                    -1.0,  0.0, -1.0,
                                                     1.0,  0.0          };

             /.
             Print the banner.
             ./
             printf( "    r       clon      z      radius    lon      lat \n" );
             printf( " -------  -------  -------  -------  -------  ------- \n" );

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

                rclon = clon[i] * rpd_c ( );

                cyllat_c ( r[i], rclon, z[i], &radius, &lon, &lat );

                printf( "%8.3f %8.3f %8.3f ", r[i], clon[i], z[i] );
                printf( "%8.3f %8.3f %8.3f\n", radius, lon * dpr_c ( ),
                                                       lat * dpr_c ( ) );

             }

             return ( 0 );
          }

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

              r       clon      z      radius    lon      lat
           -------  -------  -------  -------  -------  -------
             0.000    0.000    0.000    0.000    0.000    0.000
             1.000    0.000    0.000    1.000    0.000    0.000
             1.000   90.000    0.000    1.000   90.000    0.000
             0.000    0.000    1.000    1.000    0.000   90.000
             1.000  180.000    1.000    1.414  180.000   45.000
             1.000  -90.000    0.000    1.000  -90.000    0.000
             0.000    0.000   -1.000    1.000    0.000  -90.000
             1.000   45.000    0.000    1.000   45.000    0.000
             1.000  180.000   -1.000    1.414  180.000  -45.000
             0.000  180.000    1.000    1.000  180.000   90.000
             0.000   33.000    0.000    0.000   33.000    0.000

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman        (JPL)
       J. Diaz del Rio     (ODC Space)
       B.V. Semenov        (JPL)
       W.L. Taber          (JPL)
       E.D. Wright         (JPL)

#### Version

       -CSPICE Version 1.2.0, 02-JUL-2021 (JDR)

           Changed the input argument name "lonc" to "clon" for consistency
           with other routines.

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

       -CSPICE Version 1.1.1, 26-JUL-2016 (BVS)

           Minor headers edits.

       -CSPICE Version 1.1.0, 23-JUL-2001 (NJB)

           Removed tab characters from source file.

       -CSPICE Version 1.0.1, 08-FEB-1998 (EDW)

           Corrected and clarified header entries. Removed return call.

       -CSPICE Version 1.0.0, 25-OCT-1997 (EDW) (WLT)

#### Index_Entries

       cylindrical to latitudinal

#### Link to routine cyllat_c source file cyllat_c.c

    Fri Dec 31 18:41:03 2021