| dlatdr_c |
|
Table of contents
Procedure
dlatdr_c ( Derivative of latitudinal w.r.t. rectangular )
void dlatdr_c ( SpiceDouble x,
SpiceDouble y,
SpiceDouble z,
SpiceDouble jacobi[3][3] )
AbstractCompute the Jacobian matrix of the transformation from rectangular to latitudinal coordinates. Required_ReadingNone. KeywordsCOORDINATES DERIVATIVES MATRIX Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- x I X-coordinate of point. y I Y-coordinate of point. z I Z-coordinate of point. jacobi O Matrix of partial derivatives. Detailed_Input
x,
y,
z are the rectangular coordinates of the point at
which the Jacobian of the map from rectangular
to latitudinal coordinates is desired.
Detailed_Output
jacobi is the matrix of partial derivatives of the conversion
between rectangular and latitudinal coordinates. It
has the form
.- -.
| dr/dx dr/dy dr/dz |
| dlon/dx dlon/dy dlon/dz |
| dlat/dx dlat/dy dlat/dz |
`- -'
evaluated at the input values of x, y, and z.
ParametersNone. Exceptions
1) If the input point is on the Z-axis (X and Y = 0), the Jacobian
is undefined, the error SPICE(POINTONZAXIS) is signaled by a
routine in the call tree of this routine.
FilesNone. Particulars
When performing vector calculations with velocities it is
usually most convenient to work in rectangular coordinates.
However, once the vector manipulations have been performed
it is often desirable to convert the rectangular representations
into latitudinal coordinates to gain insights about phenomena
in this coordinate frame.
To transform rectangular velocities to derivatives of coordinates
in a latitudinal system, one uses the Jacobian of the
transformation between the two systems.
Given a state in rectangular coordinates
( x, y, z, dx, dy, dz )
the corresponding latitudinal coordinate derivatives are given by
the matrix equation:
t | t
(dr, dlon, dlat) = jacobi | * (dx, dy, dz)
|(x,y,z)
This routine computes the matrix
|
jacobi|
|(x, y, z)
Examples
The numerical results shown for this example 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) Find the latitudinal state of the Earth as seen from
Mars in the IAU_MARS reference frame at January 1, 2005 TDB.
Map this state back to rectangular coordinates as a check.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: dlatdr_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
pck00010.tpc Planet orientation and
radii
naif0009.tls Leapseconds
\begindata
KERNELS_TO_LOAD = ( 'de421.bsp',
'pck00010.tpc',
'naif0009.tls' )
\begintext
End of meta-kernel
Example code begins here.
/.
Program dlatdr_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local variables
./
SpiceDouble drectn [3];
SpiceDouble et;
SpiceDouble jacobi [3][3];
SpiceDouble lat;
SpiceDouble lon;
SpiceDouble lt;
SpiceDouble latvel [3];
SpiceDouble rectan [3];
SpiceDouble r;
SpiceDouble state [6];
/.
Load SPK, PCK and LSK kernels, use a meta kernel for
convenience.
./
furnsh_c ( "dlatdr_ex1.tm" );
/.
Look up the apparent state of earth as seen from Mars
at January 1, 2005 TDB, relative to the IAU_MARS reference
frame.
./
str2et_c ( "January 1, 2005 TDB", &et );
spkezr_c ( "Earth", et, "IAU_MARS", "LT+S", "Mars", state, < );
/.
Convert position to latitudinal coordinates.
./
reclat_c ( state, &r, &lon, &lat );
/.
Convert velocity to latitudinal coordinates.
./
dlatdr_c ( state[0], state[1], state[2], jacobi );
mxv_c ( jacobi, state+3, latvel );
/.
As a check, convert the latitudinal state back to
rectangular coordinates.
./
latrec_c ( r, lon, lat, rectan );
drdlat_c ( r, lon, lat, jacobi );
mxv_c ( jacobi, latvel, drectn );
printf( " \n" );
printf( "Rectangular coordinates:\n" );
printf( " \n" );
printf( " X (km) = %17.8e\n", state[0] );
printf( " Y (km) = %17.8e\n", state[1] );
printf( " Z (km) = %17.8e\n", state[2] );
printf( " \n" );
printf( "Rectangular velocity:\n" );
printf( " \n" );
printf( " dX/dt (km/s) = %17.8e\n", state[3] );
printf( " dY/dt (km/s) = %17.8e\n", state[4] );
printf( " dZ/dt (km/s) = %17.8e\n", state[5] );
printf( " \n" );
printf( "Latitudinal coordinates:\n" );
printf( " \n" );
printf( " Radius (km) = %17.8e\n", r );
printf( " Longitude (deg) = %17.8e\n", lon/rpd_c() );
printf( " Latitude (deg) = %17.8e\n", lat/rpd_c() );
printf( " \n" );
printf( "Latitudinal velocity:\n" );
printf( " \n" );
printf( " d Radius/dt (km/s) = %17.8e\n", latvel[0] );
printf( " d Longitude/dt (deg/s) = %17.8e\n", latvel[1]/rpd_c() );
printf( " d Latitude/dt (deg/s) = %17.8e\n", latvel[2]/rpd_c() );
printf( " \n" );
printf( "Rectangular coordinates from inverse mapping:\n" );
printf( " \n" );
printf( " X (km) = %17.8e\n", rectan[0] );
printf( " Y (km) = %17.8e\n", rectan[1] );
printf( " Z (km) = %17.8e\n", rectan[2] );
printf( " \n" );
printf( "Rectangular velocity from inverse mapping:\n" );
printf( " \n" );
printf( " dX/dt (km/s) = %17.8e\n", drectn[0] );
printf( " dY/dt (km/s) = %17.8e\n", drectn[1] );
printf( " dZ/dt (km/s) = %17.8e\n", drectn[2] );
printf( " \n" );
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
Rectangular coordinates:
X (km) = -7.60961826e+07
Y (km) = 3.24363805e+08
Z (km) = 4.74704840e+07
Rectangular velocity:
dX/dt (km/s) = 2.29520749e+04
dY/dt (km/s) = 5.37601112e+03
dZ/dt (km/s) = -2.08811490e+01
Latitudinal coordinates:
Radius (km) = 3.36535219e+08
Longitude (deg) = 1.03202903e+02
Latitude (deg) = 8.10898662e+00
Latitudinal velocity:
d Radius/dt (km/s) = -1.12116011e+01
d Longitude/dt (deg/s) = -4.05392876e-03
d Latitude/dt (deg/s) = -3.31899303e-06
Rectangular coordinates from inverse mapping:
X (km) = -7.60961826e+07
Y (km) = 3.24363805e+08
Z (km) = 4.74704840e+07
Rectangular velocity from inverse mapping:
dX/dt (km/s) = 2.29520749e+04
dY/dt (km/s) = 5.37601112e+03
dZ/dt (km/s) = -2.08811490e+01
RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) W.L. Taber (JPL) Version
-CSPICE Version 1.0.1, 01-NOV-2021 (JDR)
Edited the header to comply with NAIF standard.
Added complete code example.
-CSPICE Version 1.0.0, 13-JUL-2001 (WLT) (NJB)
Index_EntriesJacobian of rectangular w.r.t. latitudinal coordinates |
Fri Dec 31 18:41:04 2021