cspice_inedpl

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

#### Abstract

```
CSPICE_INEDPL calculates the intercept of a triaxial ellipsoid
and a plane.

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

```

#### I/O

```
Given:

a,
b,
c       are the scalar double precision lengths of the semi-axes of
a triaxial ellipsoid.  The ellipsoid is centered at the origin
and oriented so that its axes lie on the x, y and z axes.
'a', 'b', and 'c' are the lengths of the semi-axes that
respectively point in the x, y, and z directions.

plane   a scalar SPICE plane structure that might intersect
the ellipsoid. The structure has the fields:

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

the call:

cspice_inedpl, a, b, c, plane, ellipse, found

returns:

ellipse   the scalar SPICE ellipse defining the intersection of 'plane'
and the ellipsoid.

found     a scalar boolean indicating whether 'plane' intersects
the ellipsoid (true) or not (false).

```

#### 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.

;;
;; Give a position relative to an ellipsoid, calculate
;; the terminator on the ellipsoid as seen from the position.
;; As an example, use the view of Earth from the sun.
;;

;;
;; Standard SPK, LSK, PCK files.
;;
cspice_furnsh, 'standard.tm'

;;
;; Define the time to calculate the  terminator, the reference
;; frame, and the light time correction.
;;
TIME  = 'Oct 31 2002, 12:55:00 PST'
FRAME = 'J2000'
CORR  = 'LT+S'

;;
;; Convert the date string to ephemeris time.
;;
cspice_str2et, TIME, et

;;
;; calculate the position of Earth wrt the Sun.
;;
cspice_spkpos, 'EARTH', et, FRAME, CORR, 'SUN', pos, ltime

;;
;; retrieve the triaxial radii of Earth.
;;

;;
;; Normalize the position to factors of the radii.
;;

;;
;; Create the SPICE plane.
;;
cspice_nvc2pl, pos, 1.d, plane

;;
;; Calculate the intercept.
;;
plane, term, found

;;
;; Show the ellipse.
;;
print, term.center
print, term.semimajor
print, term.semiminor

;;
;; What's the length measure of the semimajor axis.
;;
print, norm( term.semimajor )

;;
;; What's the length measure of the semiminor axis?
;;
print, norm( term.semiminor )

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

IDL outputs for term.center:

0.21512031     0.15544527    0.067391641

Less than a kilometer from the center of the Earth.

IDL outputs for term.semimajor:

-3735.6136      5169.7060  -9.7794273e-12

IDL outputs for term.semiminor:

-1276.3353     -922.27592      6159.9716

IDL outputs for norm(term.semimajor):

6378.1400

The approximate value for the equatorial radius.

IDL outputs for norm(term.semiminor):

6358.0558

Approximately .021% longer than the pole axis.

```

```
None.

```

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

```

#### Version

```
-Icy Version 1.0.2, 20-JUN-2011, EDW (JPL)

Edit to example code, "cspice_unload" replaced with "cspice_kclear,"

-Icy Version 1.0.1, 16-OCT-2006, EDW (JPL)

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

```

#### Index_Entries

```
intersection of ellipsoid and plane

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