Table of contents
CSPICE_DRDLAT computes the Jacobian matrix of the transformation from
latitudinal to rectangular coordinates.
Given:
r scalar double precision describing the distance of a point from
the origin.
help, r
DOUBLE = Scalar
lon scalar double precision describing the angle of the point
measured from the XZ plane in radians.
help, lon
DOUBLE = Scalar
The angle increases in the counterclockwise sense about the +Z
axis.
lat scalar double precision describing the angle of the point
measured from the XY plane in radians.
help, lat
DOUBLE = Scalar
The angle increases in the direction of the +Z axis.
the call:
cspice_drdlat, r, lon, lat, jacobi
returns:
jacobi double precision 3x3 matrix describing the matrix of partial
derivatives of the conversion between latitudinal and
rectangular coordinates, evaluated at the input coordinates.
help, jacobi
DOUBLE = Array[3,3]
This matrix has the form
.- -.
| dx/dr dx/dlon dx/dlat |
| |
| dy/dr dy/dlon dy/dlat |
| |
| dz/dr dz/dlon dz/dlat |
`- -'
evaluated at the input values of `r', `lon' and `lat'.
Here `x', `y', and `z' are given by the familiar formulae
x = r * cos(lon) * cos(lat)
y = r * sin(lon) * cos(lat)
z = r * sin(lat).
None.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
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: drdlat_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.
PRO drdlat_ex1
;;
;; Load SPK, PCK and LSK kernels, use a meta kernel for
;; convenience.
;;
cspice_furnsh, 'drdlat_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.
;;
cspice_str2et, 'January 1, 2005 TDB', et
cspice_spkezr, 'Earth', et, 'IAU_MARS', 'LT+S', 'Mars', state, ltime
;;
;; Convert position to latitudinal coordinates.
;;
cspice_reclat, state[0:2], r, lon, lat
;;
;; Convert velocity to latitudinal coordinates.
;;
cspice_dlatdr, state[0], state[1], state[2], jacobi
cspice_mxv, jacobi, state[3:5], latvel
;;
;; As a check, convert the latitudinal state back to
;; rectangular coordinates.
;;
cspice_latrec, r, lon, lat, rectan
cspice_drdlat, r, lon, lat, jacobi
cspice_mxv, jacobi, latvel, drectn
print, ' '
print, 'Rectangular coordinates:'
print, ' '
print, format='(A,E18.8)', ' X (km) = ', state[0]
print, format='(A,E18.8)', ' Y (km) = ', state[1]
print, format='(A,E18.8)', ' Z (km) = ', state[2]
print, ' '
print, 'Rectangular velocity:'
print, ' '
print, format='(A,E18.8)', ' dX/dt (km/s) = ', state[3]
print, format='(A,E18.8)', ' dY/dt (km/s) = ', state[4]
print, format='(A,E18.8)', ' dZ/dt (km/s) = ', state[5]
print, ' '
print, 'Latitudinal coordinates:'
print, ' '
print, format='(A,E18.8)', ' Radius (km) = ', r
print, format='(A,E18.8)', ' Longitude (deg) = ', $
lon/cspice_rpd()
print, format='(A,E18.8)', ' Latitude (deg) = ', $
lat/cspice_rpd()
print, ' '
print, 'Latitudinal velocity:'
print, ' '
print, format='(A,E18.8)', ' d Radius/dt (km/s) = ', latvel[0]
print, format='(A,E18.8)', ' d Longitude/dt (deg/s) = ', $
latvel[1]/cspice_rpd()
print, format='(A,E18.8)', ' d Latitude/dt (deg/s) = ', $
latvel[2]/cspice_rpd()
print, ' '
print, 'Rectangular coordinates from inverse mapping:'
print, ' '
print, format='(A,E18.8)', ' X (km) = ', rectan[0]
print, format='(A,E18.8)', ' Y (km) = ', rectan[1]
print, format='(A,E18.8)', ' Z (km) = ', rectan[2]
print, ' '
print, 'Rectangular velocity from inverse mapping:'
print, ' '
print, format='(A,E18.8)', ' dX/dt (km/s) = ', drectn[0]
print, format='(A,E18.8)', ' dY/dt (km/s) = ', drectn[1]
print, format='(A,E18.8)', ' dZ/dt (km/s) = ', drectn[2]
print, ' '
END
When this program was executed on a Mac/Intel/IDL8.x/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
It is often convenient to describe the motion of an object
in latitudinal coordinates. It is also convenient to manipulate
vectors associated with the object in rectangular coordinates.
The transformation of a latitudinal state into an equivalent
rectangular state makes use of the Jacobian of the
transformation between the two systems.
Given a state in latitudinal coordinates,
( r, lon, lat, dr, dlon, dlat )
the velocity in rectangular coordinates is given by the matrix
equation
t | t
(dx, dy, dz) = jacobi| * (dr, dlon, dlat)
|(r,lon,lat)
This routine computes the matrix
|
jacobi|
|(r,lon,lat)
1) If any of the input arguments, `r', `lon' or `lat', is
undefined, an error is signaled by the IDL error handling
system.
2) If any of the input arguments, `r', `lon' or `lat', is not of
the expected type, or it does not have the expected dimensions
and size, an error is signaled by the Icy interface.
3) If the output argument `jacobi' is not a named variable, an
error is signaled by the Icy interface.
None.
None.
ICY.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Icy Version 1.0.1, 01-NOV-2021 (JDR)
Edited the -Examples section to comply with NAIF standard.
Added complete code example.
Updated `r' argument name in -I/O, which in previous version
was `radius'.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections.
Removed reference to the routine's corresponding CSPICE header from
-Abstract section.
Added arguments' type and size information in the -I/O section.
-Icy Version 1.0.0, 11-NOV-2013 (EDW)
Jacobian of rectangular w.r.t. latitudinal coordinates
|