cspice_pjelpl

 Abstract I/O Examples Particulars Required Reading Version Index_Entries
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```

#### Abstract

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

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

```

#### I/O

```
Given:

elin    a SPICE ellipse structure. The structure has the fields:

center:    [3-array double]
semiMajor: [3-array double]
semiMinor: [3-array double]

plane   a SPICE plane structure. The structure has the fields:

normal:   [3-array double]
constant: [scalar 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:

cspice_pjelpl, elin, plane, elout

returns:

elout    the SPICE ellipse structure that represents the geometric
ellipse resulting from orthogonally projecting the ellipse
represented by 'elin' onto the plane represented by 'plane'.
The structure has the fields:

center:    [3-array double]
semiMajor: [3-array double]
semiMinor: [3-array double]

```

#### 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.d,  1.d,  1.d ]
vect1   = [ 2.d,  0.d,  0.d ]
vect2   = [ 0.d,  1.d,  1.d ]
normal  = [ 0.d,  0.d,  1.d ]

;;
;; Create a plane using a constant value of 0...
;;
cspice_nvc2pl, normal, 0.d, plane

;;
;; ...and an ellipse.
;;
cspice_cgv2el, center, vect1, vect2, elin

;;
;; Project the ellipse onto the plane.
;;
cspice_pjelpl, elin, plane, elout

;;
;; Output the ellipse in the plane.
;;
print, 'Center    : ', elout.center
print, 'Semi-minor: ', elout.semiminor
print, 'Semi-major: ', elout.semimajor

IDL outputs for the components of 'elout':

Center    :  1.0000000   1.0000000   0.0000000
Semi-minor:  0.0000000   1.0000000   0.0000000
Semi-major:  2.0000000   0.0000000   0.0000000

```

#### 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.

```

```
ICY.REQ
ELLIPSES.REQ
PLANES.REQ

```

#### Version

```
-Icy Version 1.0.1, 13-JUN-2011, EDW (JPL)

Edits to comply with NAIF standard for Icy headers. Particulars section
now parallels Mice version.

-Icy Version 1.0.0, 16-JUN-2003, EDW (JPL)

```

#### Index_Entries

```
project ellipse onto plane

```
`Wed Apr  5 17:58:02 2017`