| recsph_c |
|
Table of contents
Procedure
recsph_c ( Rectangular to spherical coordinates )
void recsph_c ( ConstSpiceDouble rectan[3],
SpiceDouble * r,
SpiceDouble * colat,
SpiceDouble * slon )
AbstractConvert from rectangular coordinates to spherical coordinates. Required_ReadingNone. KeywordsCONVERSION COORDINATES Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- rectan I Rectangular coordinates of a point. r O Distance of the point from the origin. colat O Angle of the point from the Z-axis in radians slon O Longitude of the point in radians. Detailed_Inputrectan are the rectangular coordinates of a point. Detailed_Output
r is the distance of the point from the origin.
colat is the angle between the point and the positive z-axis in
radians. The range of `colat' is [0, pi].
slon is the longitude of the point in radians. This is the
angle between the positive X-axis and the orthogonal
projection of the point onto the XY plane. `slon'
increases in the counterclockwise sense about the
positive Z-axis. The range of `slon' is [-pi, pi].
ParametersNone. ExceptionsError free. FilesNone. ParticularsThis routine returns the spherical coordinates of a point whose position is input in rectangular 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. 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: recsph_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 recsph_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local variables.
./
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 ( "recsph_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, < );
/.
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 rectangular coordinates
and the corresponding spherical coordinates.
Corresponding rectangular and spherical coordinates are
listed to three decimal places. Output angles are in degrees.
Example code begins here.
/.
Program recsph_ex2
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local parameters.
./
#define NREC 11
/.
Local variables.
./
SpiceDouble colat;
SpiceDouble radius;
SpiceDouble slon;
SpiceInt i;
/.
Define the input rectangular coordinates.
./
SpiceDouble rectan [NREC][3] = {
{ 0.0, 0.0, 0.0},
{ 1.0, 0.0, 0.0},
{ 0.0, 1.0, 0.0},
{ 0.0, 0.0, 1.0},
{-1.0, 0.0, 0.0},
{ 0.0, -1.0, 0.0},
{ 0.0, 0.0, -1.0},
{ 1.0, 1.0, 0.0},
{ 1.0, 0.0, 1.0},
{ 0.0, 1.0, 1.0},
{ 1.0, 1.0, 1.0} };
/.
Print the banner.
./
printf( " rect[0] rect[1] rect[2] radius colat slon\n" );
printf( " ------- ------- ------- ------- ------- -------\n" );
/.
Do the conversion. Output angles in degrees.
./
for ( i = 0; i < NREC; i++ )
{
recsph_c ( rectan[i], &radius, &colat, &slon );
printf( "%8.3f %8.3f %8.3f ", rectan[i][0], rectan[i][1],
rectan[i][2] );
printf( "%8.3f %8.3f %8.3f\n", radius, colat * dpr_c(),
slon * dpr_c() );
}
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
rect[0] rect[1] rect[2] radius colat slon
------- ------- ------- ------- ------- -------
0.000 0.000 0.000 0.000 0.000 0.000
1.000 0.000 0.000 1.000 90.000 0.000
0.000 1.000 0.000 1.000 90.000 90.000
0.000 0.000 1.000 1.000 0.000 0.000
-1.000 0.000 0.000 1.000 90.000 180.000
0.000 -1.000 0.000 1.000 90.000 -90.000
0.000 0.000 -1.000 1.000 180.000 0.000
1.000 1.000 0.000 1.414 90.000 45.000
1.000 0.000 1.000 1.414 45.000 0.000
0.000 1.000 1.000 1.414 45.000 90.000
1.000 1.000 1.000 1.732 54.736 45.000
RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionN.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, 10-AUG-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 1.1.2, 26-JUL-2016 (BVS)
Minor headers edits.
-CSPICE Version 1.1.1, 07-JAN-2002 (NJB) (EDW)
Fixed description of slon in -Brief_I/O and Detailed_I/O
header sections.
-CSPICE Version 1.1.0, 22-OCT-1998 (NJB)
Made input coordinate array const.
-CSPICE Version 1.0.0, 08-FEB-1998 (EDW) (WLT)
Index_Entriesrectangular to spherical coordinates |
Fri Dec 31 18:41:11 2021