| reclat_c |
|
Table of contents
Procedure
reclat_c ( Rectangular to latitudinal coordinates )
void reclat_c ( ConstSpiceDouble rectan[3],
SpiceDouble * radius,
SpiceDouble * lon,
SpiceDouble * lat )
AbstractConvert from rectangular coordinates to latitudinal coordinates. Required_ReadingNone. KeywordsCONVERSION COORDINATES Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- rectan I Rectangular coordinates of a point. radius O Distance of the point from the origin. lon O Longitude of the point in radians. lat O Latitude of the point in radians. Detailed_Input
rectan are the rectangular coordinates of the input point.
`rectan' is a 3-vector.
Detailed_Output
radius is the distance of the point from the origin.
The units associated with `radius' are those
associated with the input `rectan'.
lon is the longitude of the input point. This is angle
between the prime meridian and the meridian
containing `rectan'. The direction of increasing
longitude is from the +X axis towards the +Y axis.
`lon' is output in radians. The range of `lon'
is [-pi, pi].
lat is the latitude of the input point. This is the angle
from the XY plane of the ray from the origin through the
point.
`lat' is output in radians. The range of `lat'
is [-pi/2, pi/2].
ParametersNone. Exceptions
Error free.
1) If the X and Y components of `rectan' are both zero, the
longitude is set to zero.
2) If `rectan' is the zero vector, longitude and latitude are
both set to zero.
FilesNone. ParticularsThis routine returns the latitudinal coordinates of a point whose position is input in rectangular 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 thes 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 rectangular
coordinates.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: reclat_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 reclat_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local variables
./
SpiceDouble et;
SpiceDouble lat;
SpiceDouble lon;
SpiceDouble lt;
SpiceDouble pos [3];
SpiceDouble radius;
SpiceDouble rectan [3];
/.
Load SPK and LSK kernels, use a meta kernel for
convenience.
./
furnsh_c ( "reclat_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 to rectangular coordinates.
./
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( "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
Latitudinal coordinates:
Radius (km): 403626.33912495
Longitude (deg): -98.34959789
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 rectangular coordinates
and the corresponding latitudinal coordinates.
Corresponding rectangular and latitudinal coordinates are
listed to three decimal places. Output angles are in degrees.
Example code begins here.
/.
Program reclat_ex2
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local parameters.
./
#define NREC 11
/.
Local variables.
./
SpiceDouble lat;
SpiceDouble lon;
SpiceDouble radius;
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 lon lat\n" );
printf( " ------- ------- ------- ------- ------- -------\n" );
/.
Do the conversion. Output angles are in degrees.
./
for ( i = 0; i < NREC; i++ )
{
reclat_c ( rectan[i], &radius, &lon, &lat );
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, lon * dpr_c ( ),
lat * 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 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
0.000 1.000 0.000 1.000 90.000 0.000
0.000 0.000 1.000 1.000 0.000 90.000
-1.000 0.000 0.000 1.000 180.000 0.000
0.000 -1.000 0.000 1.000 -90.000 0.000
0.000 0.000 -1.000 1.000 0.000 -90.000
1.000 1.000 0.000 1.414 45.000 0.000
1.000 0.000 1.000 1.414 0.000 45.000
0.000 1.000 1.000 1.414 90.000 45.000
1.000 1.000 1.000 1.732 45.000 35.264
RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) E.D. Wright (JPL) Version
-CSPICE Version 1.3.0, 10-AUG-2021 (JDR)
Changed input argument names "longitude" and "latitude to "lon"
and "lat" for consistency with other routines.
Edited the header to comply with NAIF standard. Added
complete code example based on existing example.
Added -Particulars section.
-CSPICE Version 1.2.1, 30-JUL-2003 (NJB)
Various header changes were made to improve clarity. Some
minor header corrections were made.
-CSPICE Version 1.2.0, 28-AUG-2001 (NJB)
Removed tab characters from source file. Now includes
interface macro header SpiceZim.h.
-CSPICE Version 1.1.0, 21-OCT-1998 (NJB)
Made input vector const.
-CSPICE Version 1.0.0, 08-FEB-1998 (EDW)
Index_Entriesrectangular to latitudinal coordinates |
Fri Dec 31 18:41:11 2021