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Abstract
I/O
Examples
Particulars
Required Reading
Version
Index_Entries

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.
      ;;
      cspice_bodvrd, 'EARTH', 'RADII', 3, radii

      ;;
      ;; Normalize the position to factors of the radii.
      ;;
      pos = [ pos[0]/radii[0]^2, $
              pos[1]/radii[1]^2, $
              pos[2]/radii[2]^2 ]

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

      ;;
      ;; Calculate the intercept.
      ;;
      cspice_inedpl, radii[0],        $
                     radii[1],        $
                     radii[2],        $
                     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.

Particulars


   None.

Required Reading


   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,"
       and header.

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

       Added cspice_unload to example code.

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

Index_Entries


   intersection of ellipsoid and plane




Wed Apr  5 17:58:02 2017