| latcyl_c |
|
Table of contents
Procedure
latcyl_c ( Latitudinal to cylindrical coordinates )
void latcyl_c ( SpiceDouble radius,
SpiceDouble lon,
SpiceDouble lat,
SpiceDouble * r,
SpiceDouble * clon,
SpiceDouble * z )
AbstractConvert from latitudinal coordinates to cylindrical coordinates. Required_ReadingNone. KeywordsCONVERSION COORDINATES Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- radius I Distance of a point from the origin. lon I Angle of the point from the XZ plane in radians. lat I Angle of the point from the XY plane in radians. r O Distance of the point from the z axis. clon O Angle of the point from the XZ plane in radians. z O Height of the point above the XY plane. Detailed_Inputradius is the distance of a point from the origin. lon is the angle of the point from the XZ plane in radians. lat is the angle of the point from the XY plane in radians. Detailed_Output
r is the distance of the point from the z axis.
clon is the angle of the point from the XZ plane in radians.
`clon' is set equal to `lon'.
z is the height of the point above the XY plane.
ParametersNone. ExceptionsError free. FilesNone. ParticularsThis routine returns the cylindrical coordinates of a point whose position is input 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 latitudinal 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: latcyl_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 latcyl_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 ( "latcyl_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 latitudinal
coordinates.
./
reclat_c ( pos, &radius, &lon, &lat );
/.
Convert the latitudinal coordinates to cylindrical.
./
latcyl_c ( radius, lon, lat, &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( "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( "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
Latitudinal coordinates:
Radius (km): 403626.33912495
Longitude (deg): -98.34959789
Latitude (deg): -18.26566077
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 latitudinal coordinates
and the corresponding cylindrical coordinates.
Corresponding latitudinal and cylindrical coordinates are
listed to three decimal places. Input and output angles are
in degrees.
Example code begins here.
/.
Program latcyl_ex2
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local parameters.
./
#define NREC 11
/.
Local variables.
./
SpiceDouble clon;
SpiceDouble r;
SpiceDouble rlat;
SpiceDouble rlon;
SpiceDouble z;
SpiceInt i;
/.
Define the input latitudinal 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 lon [NREC] = { 0.0, 0.0, 90.0,
0.0, 180.0, -90.0,
0.0, 45.0, 180.0,
180.0, 33.0 };
SpiceDouble lat [NREC] = { 90.0, 0.0, 0.0,
90.0, 45.0, 0.0,
-90.0, 0.0, -45.0,
90.0, 0.0 };
/.
Print the banner.
./
printf( " radius lon lat r clon z \n" );
printf( " ------- ------- ------- ------- ------- -------\n" );
/.
Do the conversion. Output angles in degrees.
./
for ( i = 0; i < NREC; i++ )
{
rlon = lon[i] * rpd_c ( );
rlat = lat[i] * rpd_c ( );
latcyl_c ( radius[i], rlon, rlat, &r, &clon, &z );
printf( "%8.3f %8.3f %8.3f ", radius[i], lon[i], lat[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 lon lat r clon z
------- ------- ------- ------- ------- -------
0.000 0.000 90.000 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
1.000 0.000 90.000 0.000 0.000 1.000
1.414 180.000 45.000 1.000 180.000 1.000
1.000 -90.000 0.000 1.000 -90.000 0.000
1.000 0.000 -90.000 0.000 0.000 -1.000
1.000 45.000 0.000 1.000 45.000 0.000
1.414 180.000 -45.000 1.000 180.000 -1.000
1.000 180.000 90.000 0.000 180.000 1.000
0.000 33.000 0.000 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 latcyl_ex3
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local variables
./
SpiceDouble clon;
SpiceDouble lat;
SpiceDouble lon;
SpiceDouble radius;
SpiceDouble r;
SpiceDouble z;
/.
Define the point whose projection is to be
computed.
./
radius = 100.0;
lon = 45.0 * rpd_c ( );
lat = -12.5 * rpd_c ( );
/.
Convert the latitudinal coordinates to cylindrical.
./
latcyl_c ( radius, lon, lat, &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) W.L. Taber (JPL) E.D. Wright (JPL) Version
-CSPICE Version 1.1.0, 04-JUL-2021 (JDR)
Edited the header to comply with NAIF standard.
Added complete code examples.
Changed the input argument name "lonc" to "clon" for consistency
with other routines.
-CSPICE Version 1.0.1, 26-JUL-2016 (BVS)
Minor headers edits.
-CSPICE Version 1.0.0, 08-FEB-1998 (EDW) (WLT)
Index_Entrieslatitudinal to cylindrical coordinates |
Fri Dec 31 18:41:08 2021