Table of contents
CSPICE_RECLAT converts rectangular (Cartesian) coordinates to
latitudinal coordinates. All coordinates are expressed as
double precision values.
Given:
rectan the array(s) containing the rectangular coordinates of the
position or set of positions.
[3,n] = size(rectan); double = class(rectan)
the call:
[radius, lon, lat] = cspice_reclat(rectan)
returns:
radius the value(s) describing the distance of the position
from the origin.
[1,n] = size(radius); double = class(radius)
lon the value(s) describing the angle of the position from
the XZ plane measured in radians.
[1,n] = size(lon); double = class(lon)
lat the value(s) describing the angle of the position from the
XY plane measured in radians.
[1,n] = size(lat); double = class(lat)
The argument `radius' returns in the same units associated
with `rectan'.
`radius', `lon', and `lat' return with
the same vectorization measure, N, as `rectan'.
None.
Any numerical results shown for these examples may differ between
platforms as the results depend on the SPICE kernels used as input
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.
function reclat_ex1()
%
% Load an SPK and leapseconds kernels.
%
cspice_furnsh( 'reclat_ex1.tm' )
%
% Convert the time to ET.
%
et = cspice_str2et( '2017 Mar 20' );
%
% Retrieve the position of the moon seen from earth at `et'
% in the J2000 frame without aberration correction.
%
[pos, et] = cspice_spkpos( 'MOON', et, 'J2000', 'NONE', 'EARTH' );
fprintf( 'Original rectangular coordinates:\n' )
fprintf( ' X (km): %20.8f\n', pos(1) )
fprintf( ' Y (km): %20.8f\n', pos(2) )
fprintf( ' Z (km): %20.8f\n', pos(3) )
%
% Convert the position vector `pos' to latitudinal
% coordinates.
%
[radius, lon, lat] = cspice_reclat(pos);
fprintf( '\n' )
fprintf( 'Latitudinal coordinates:\n' )
fprintf( ' Radius (km): %20.8f\n', radius )
fprintf( ' Longitude (deg): %20.8f\n', lon * cspice_dpr )
fprintf( ' Latitude (deg): %20.8f\n', lat * cspice_dpr )
%
% Convert the latitudinal to rectangular.
%
[rectan] = cspice_latrec( radius, lon, lat);
fprintf( '\n' )
fprintf( 'Rectangular coordinates from cspice_latrec:\n' )
fprintf( ' X (km): %20.8f\n', rectan(1) )
fprintf( ' Y (km): %20.8f\n', rectan(2) )
fprintf( ' Z (km): %20.8f\n', rectan(3) )
%
% It's always good form to unload kernels after use,
% particularly in MATLAB due to data persistence.
%
cspice_kclear
When this program was executed on a Mac/Intel/Octave6.x/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 cspice_latrec:
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.
function reclat_ex2()
%
% Define eleven sets of rectangular coordinates.
%
rec = [ [ 0., 1., 0., 0., -1., 0., 0., 1., 1., 0., 1. ]; ...
[ 0., 0., 1., 0., 0., -1., 0., 1., 0., 1., 1. ]; ...
[ 0., 0., 0., 1., 0., 0., -1., 0., 1., 1., 1. ] ];
%
% ...convert the rectangular coordinates to latitudinal coordinates
%
[radius, lon, lat] = cspice_reclat(rec);
%
% Convert `lon' and `lat' to degrees.
%
lon = lon * cspice_dpr;
lat = lat * cspice_dpr;
%
% Create an array of values for output.
%
output = [ radius; lon; lat; rec ];
%
% Output banner.
%
disp(' r lon lat rect(1) rect(2) rect(3)')
disp(' ------- ------- ------- ------- ------- -------')
txt = sprintf( '%8.3f %8.3f %8.3f %8.3f %8.3f %8.3f\n', output );
disp( txt )
When this program was executed on a Mac/Intel/Octave6.x/64-bit
platform, the output was:
r lon lat rect(1) rect(2) rect(3)
------- ------- ------- ------- ------- -------
0.000 0.000 0.000 0.000 0.000 0.000
1.000 0.000 0.000 1.000 0.000 0.000
1.000 90.000 0.000 0.000 1.000 0.000
1.000 0.000 90.000 0.000 0.000 1.000
1.000 180.000 0.000 -1.000 0.000 0.000
1.000 -90.000 0.000 0.000 -1.000 0.000
1.000 0.000 -90.000 0.000 0.000 -1.000
1.414 45.000 0.000 1.000 1.000 0.000
1.414 0.000 45.000 1.000 0.000 1.000
1.414 90.000 45.000 0.000 1.000 1.000
1.732 45.000 35.264 1.000 1.000 1.000
This 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.
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.
3) If the input argument `rectan' is undefined, an error is
signaled by the Matlab error handling system.
4) If the input argument `rectan' is not of the expected type, or
it does not have the expected dimensions and size, an error is
signaled by the Mice interface.
None.
None.
MICE.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Mice Version 1.1.0, 10-AUG-2021 (EDW) (JDR)
Changed output arguments "longitude" and "latitude" to
"lon" and "lat" for consistency with other routines.
Edited the header to comply with NAIF standard. Added
meta-kernel to example #1. Updated code example #1 to produce
formatted output and added a call to cspice_kclear. Added the
problem statement to both examples.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections, and
completed -Particulars section.
Eliminated use of "lasterror" in rethrow.
Removed reference to the function's corresponding CSPICE header from
-Required_Reading section.
-Mice Version 1.0.1, 01-DEC-2014 (EDW)
Edited -I/O section to conform to NAIF standard for Mice
documentation.
-Mice Version 1.0.0, 22-NOV-2005 (EDW)
rectangular to latitudinal coordinates
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