cspice_sphcyl

 Abstract I/O Examples Particulars Required Reading Version Index_Entries

#### Abstract

```
CSPICE_SPHCYL converts spherical coordinates to cylindrical
coordinates.

```

#### I/O

```
Given:

radius   the value(s) describing the distance of the position
from the origin.

[1,n] = size(radius); double = class(radius)

colat    the value(s) describing the angle between the point and the
positive z-axis, measured in radians (also referred to
as the polar angle).

[1,n] = size(colat); double = class(colat)

slon     the value(s) describing the angle of the projection of the
point to the XY plane from the positive X-axis, measured
in radians, with range:

-pi < slon <= pi

The positive Y-axis is at longitude PI/2 radians.

[1,n] = size(slon); double = class(slon)

the call:

[ r, lonc, z] = cspice_sphcyl( radius, colat, slon)

returns:

r      the value(s) describing the distance of the point of
interest from z axis.

[1,n] = size(r); double = class(r)

lonc   the value(s) describing the cylindrical angle of the point of
interest from the XZ plane measured in radians.

[1,n] = size(lonc); double = class(lonc)

z      the value(s) describing the height of the point above
the XY plane.

[1,n] = size(z); double = class(z)

The arguments 'r' and 'z' return in the same units associated
with 'radius'.

'r', 'lonc', and 'z' return with the same vectorization
measure, N, as 'radius', 'colat', and 'slon'.

```

#### Examples

```
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.

Example (1):

%
% Load an SPK, leapseconds, and PCK kernel set.
%
cspice_furnsh( 'standard.tm' )

%
% Create a vector of scalar times.
%
et = [0:2]*2.*cspice_spd;

%
% 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' );

%
% Convert the array of position vectors 'pos' to spherical
% coordinates.
%
[radius, colat, lon] = cspice_recsph(pos);

%
% Convert the spherical coords to cylindrical.
%
[r, lonc, z] = cspice_sphcyl(radius, colat, lon);

%
% Convert the cylindrical to rectangular.
%
[rectan] = cspice_cylrec(r, lonc, z);

%
% Calculate the relative error against the original position
% vectors.
%
(rectan-pos) ./ pos

MATLAB outputs:

1.0e-14 *

0  -0.03701547067225   0.63783453323816
0.02182376758148   0.01641520435413  -0.01531271963894
-0.01912147275010  -0.04855217028457   0.02039513446643

The relative error between the original array of position vectors
and those that resulted from the various coordinate conversion
has magnitude on the order of 10^(-14).

Example (2):

%
% Define six sets of spherical coordinates, 'slon' and 'colat'
% expressed in degrees - converted to radians by use of cspice_rpd.
%
radius = [  1.,  1., 1.4142, 1.4142, 1.  , 0. ];
colat  = [ 90., 90., 45.   , 135.  , 0.  , 0. ] * cspice_rpd;
slon   = [  0., 90., 180.  , 180.  , 180., 33.] * cspice_rpd;

%
% ...convert the spherical coordinates to cylindrical coordinates
%
[r, lonc, z] = cspice_sphcyl(radius, colat, slon);

%
% ...convert angular measure to degrees.
%
colat = colat * cspice_dpr;
lonc = lonc   * cspice_dpr;
slon = slon   * cspice_dpr;

%
% Output banner.
%
disp('     r         lonc        z        radius     slon       colat  ')
disp('  --------   --------   --------   --------   --------   --------')

%
% Create an array of values for output.
%
output = [ r; lonc; z; radius; slon; colat ];
txt   = sprintf( '%10.4f %10.4f %10.4f %10.4f %10.4f %10.4f\n', output);
disp( txt )

%
% It's always good form to unload kernels after use,
% particularly in MATLAB due to data persistence.
%
cspice_kclear

MATLAB outputs:

r         lonc        z        radius      lon       colat
--------   --------   --------   --------   --------   --------
1.0000     0.0000     0.0000     1.0000     0.0000    90.0000
1.0000    90.0000     0.0000     1.0000    90.0000    90.0000
1.0000   180.0000     1.0000     1.4142   180.0000    45.0000
1.0000   180.0000    -1.0000     1.4142   180.0000   135.0000
0.0000   180.0000     1.0000     1.0000   180.0000     0.0000
0.0000    33.0000     0.0000     0.0000    33.0000     0.0000

```

```
None.

```

#### Required Reading

```
For important details concerning this module's function, please refer to
the CSPICE routine sphcyl_c.

MICE.REQ

```

#### Version

```
-Mice Version 1.0.1, 01-DEC-2014, EDW (JPL)

Edited I/O section to conform to NAIF standard for Mice documentation.

-Mice Version 1.0.0, 12-DEC-2005, EDW (JPL)

```

#### Index_Entries

```
spherical to cylindrical coordinates

```
`Wed Apr  5 18:00:34 2017`