| sphcyl_c |
|
Table of contents
Procedure
sphcyl_c ( Spherical to cylindrical coordinates )
void sphcyl_c ( SpiceDouble radius,
SpiceDouble colat,
SpiceDouble slon,
SpiceDouble * r,
SpiceDouble * clon,
SpiceDouble * z )
AbstractConvert from spherical coordinates to cylindrical coordinates. Required_ReadingNone. KeywordsCONVERSION COORDINATES Brief_I/OVARIABLE I/O DESCRIPTION -------- --- ------------------------------------------------- radius I Distance of point from origin. colat I Polar angle (co-latitude in radians) of point. slon I Azimuthal angle (longitude) of point (radians). r O Distance of point from Z axis. clon O Angle (radians) of point from XZ plane. z O Height of point above XY plane. Detailed_Inputradius is the distance of the point from origin. colat is the polar angle (co-latitude in radians) of the point. slon is the azimuthal angle (longitude) of the point (radians). Detailed_Output
r is the distance of the point of interest from Z axis.
clon is the cylindrical angle (radians) of the point from the
XZ plane. `clon' is set equal to `slon'.
z is the height of the point above XY plane.
ParametersNone. ExceptionsError free. FilesNone. ParticularsThis returns the cylindrical coordinates of a point whose position is input through spherical coordinates. 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 cylindrical and
rectangular coordinates.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: sphcyl_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 sphcyl_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local variables
./
SpiceDouble clon;
SpiceDouble colat;
SpiceDouble et;
SpiceDouble lt;
SpiceDouble pos [3];
SpiceDouble r;
SpiceDouble radius;
SpiceDouble rectan [3];
SpiceDouble slon;
SpiceDouble z;
/.
Load SPK and LSK kernels, use a meta kernel for
convenience.
./
furnsh_c ( "sphcyl_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 cylindrical.
./
sphcyl_c ( radius, colat, slon, &r, &clon, &z );
/.
Convert the cylindrical coordinates to rectangular.
./
cylrec_c ( r, clon, z, 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( "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( "Rectangular coordinates from cylrec_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
Cylindrical coordinates:
Radius (km): 383289.01777726
Longitude (deg): -98.34959789
Z (km): -126505.93063865
Rectangular coordinates from cylrec_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 cylindrical coordinates.
Corresponding spherical and cylindrical coordinates are
listed to three decimal places. Input and output angles are
in degrees.
Example code begins here.
/.
Program sphcyl_ex2
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local parameters.
./
#define NREC 11
/.
Local variables.
./
SpiceDouble clon;
SpiceDouble r;
SpiceDouble rcolat;
SpiceDouble rslon;
SpiceDouble z;
SpiceInt i;
/.
Define the input spherical coordinates. Angles in degrees.
./
SpiceDouble radius [NREC] = { 0.0, 1.0, 1.0,
1.0, 1.4142, 1.0,
1.0, 1.0, 1.4142,
1.0, 0.0 };
SpiceDouble colat [NREC] = { 0.0, 90.0, 90.0,
0.0, 45.0, 90.0,
180.0, 90.0, 135.0,
0.0, 90.0 };
SpiceDouble slon [NREC] = { 0.0, 0.0, 90.0,
0.0, 180.0, -90.0,
0.0, 45.0, 180.0,
180.0, 33.0 };
/.
Print the banner.
./
printf( " radius colat slon r clon z\n" );
printf( " ------- ------- ------- ------- ------- -------\n" );
/.
Do the conversion. Output angles in degrees.
./
for ( i = 0; i < NREC; i++ )
{
rcolat = colat[i] * rpd_c ( );
rslon = slon[i] * rpd_c ( );
sphcyl_c ( radius[i], rcolat, rslon, &r, &clon, &z );
printf( "%8.3f %8.3f %8.3f ", radius[i], colat[i], slon[i] );
printf( "%8.3f %8.3f %8.3f\n", r, clon * dpr_c ( ), z );
}
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
radius colat slon r clon z
------- ------- ------- ------- ------- -------
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 1.000 90.000 0.000
1.000 0.000 0.000 0.000 0.000 1.000
1.414 45.000 180.000 1.000 180.000 1.000
1.000 90.000 -90.000 1.000 -90.000 0.000
1.000 180.000 0.000 0.000 0.000 -1.000
1.000 90.000 45.000 1.000 45.000 0.000
1.414 135.000 180.000 1.000 180.000 -1.000
1.000 0.000 180.000 0.000 180.000 1.000
0.000 90.000 33.000 0.000 33.000 0.000
3) Other than the obvious conversion between coordinate systems
this routine could be used to obtain the axial projection
from a sphere to a cylinder about the z-axis that contains
the equator of the sphere.
Such a projection is valuable because it preserves the
areas between regions on the sphere and their projections to
the cylinder.
Example code begins here.
/.
Program sphcyl_ex3
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local variables
./
SpiceDouble clon;
SpiceDouble colat;
SpiceDouble radius;
SpiceDouble r;
SpiceDouble slon;
SpiceDouble z;
/.
Define the point whose projection is to be
computed.
./
radius = 100.0;
slon = 45.0 * rpd_c();
colat = 102.5 * rpd_c();
/.
Convert the spherical coordinates to cylindrical.
./
sphcyl_c ( radius, colat, slon, &r, &clon, &z );
printf( "Coordinates of the projected point on cylinder:\n" );
printf( " \n" );
printf( " Radius (km): %22.11f\n", r );
printf( " Longitude (deg): %22.11f\n", clon*dpr_c() );
printf( " Z (km): %22.11f\n", z );
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
Coordinates of the projected point on cylinder:
Radius (km): 97.62960071199
Longitude (deg): 45.00000000000
Z (km): -21.64396139381
RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionJ. Diaz del Rio (ODC Space) B.V. Semenov (JPL) E.D. Wright (JPL) Version
-CSPICE Version 1.1.0, 05-JUL-2021 (JDR)
Changed the output argument name "lon" to "clon" 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)
Index_Entriesspherical to cylindrical coordinates |
Fri Dec 31 18:41:12 2021