cspice_pjelpl

 Abstract I/O Examples Particulars Required Reading Version Index_Entries

Abstract

```
CSPICE_PJELPL orthogonally projects an ellipse onto a plane.

```

I/O

```
Given:

elin    a structure describing a SPICE ellipse.

[1,1] = size(elin); struct = class(elin)

The structure has the fields:

center:    [3x1 double]
semiMajor: [3x1 double]
semiMinor: [3x1 double]

plane   a structure describing a SPICE plane.

[1,1] = size(plane); struct = class(plane)

The structure has the fields:

normal:     [3x1 double]
constant:   [1x1 double]

are, respectively, a SPICE ellipse and a SPICE plane. The
geometric ellipse represented by 'elin' is to be orthogonally
projected onto the geometric plane represented by 'plane'.

the call:

elout = cspice_pjelpl( elin, plane )

returns:

elout   the SPICE ellipse that represents the geometric
ellipse resulting from orthogonally projecting the ellipse
represented by 'elin' onto the plane represented by 'plane'.

[1,1] = size(elout); struct = class(elout)

```

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.

%
% Assign the values for plane/ellipse definition
% vectors.
%
center  = [ 1,  1,  1 ]';
vect1   = [ 2,  0,  0 ]';
vect2   = [ 0,  1,  1 ]';
normal  = [ 0,  0,  1 ]';

%
% Create a plane using a constant value of 0...
%
plane = cspice_nvc2pl( normal, 0 );

%
% ...and an ellipse.
%
elin = cspice_cgv2el( center, vect1, vect2 );

%
% Project the ellipse onto the plane.
%
elout = cspice_pjelpl( elin, plane );

%
% Output the ellipse in the plane.
%
fprintf( 'Center    :  %f  %f  %f\n', elout.center    )
fprintf( 'Semi-minor:  %f  %f  %f\n', elout.semiMinor )
fprintf( 'Semi-major:  %f  %f  %f\n', elout.semiMajor )

MATLAB outputs:

Center    :  1.000000  1.000000  0.000000
Semi-minor:  0.000000  1.000000  0.000000
Semi-major:  2.000000  0.000000  0.000000

```

Particulars

```
Projecting an ellipse orthogonally onto a plane can be thought of
finding the points on the plane that are `under' or `over' the
ellipse, with the `up' direction considered to be perpendicular
to the plane.  More mathematically, the orthogonal projection is
the set of points Y in the plane such that for some point X in
the ellipse, the vector Y - X is perpendicular to the plane.
The orthogonal projection of an ellipse onto a plane yields
another ellipse.

```

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

MICE.REQ
ELLIPSES.REQ
PLANES.REQ

```

Version

```
-Mice Version 1.0.0, 11-JUN-2013, EDW (JPL)

```

Index_Entries

```
project ellipse onto plane

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