CSPICE_SURFNM computes the double precision, outwardpointing
normal unit 3vector at a point defined on the surface of an
ellipsoid.
For important details concerning this module's function, please refer to
the CSPICE routine surfnm_c.
Given:
a, the scalar double precision values of the ellipsoid's
b, triaxial radii ellipsoid, where:
c
'a' is length in kilometers of the semiaxis of the ellipsoid
parallel to the xaxis of the bodyfixed reference frame
'b' is length in kilometers of the semiaxis of the ellipsoid
parallel to the yaxis of the bodyfixed reference frame
'c' is length in kilometers of the semiaxis of the ellipsoid
parallel to the zaxis of the bodyfixed reference frame
point a double precision 3vector defining a location on
the ellipsoid
the call:
cspice_surfnm, a, b, c, point, normal
returns:
normal a double precision unit 3vector normal to the
ellipsoid at 'point' in the direction away from the
ellipsoid
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.
;;
;; Define the radii of an ellipsoid.
;;
a = 1.d
b = 2.d
c = 3.d
;;
;; Select a location.
;;
point = [ 0.d, 0.d, 3.d ]
;;
;; calculate the surface normal to the ellipsoid at 'point'.
;;
cspice_surfnm, a, b, c, point, out_norm
print, out_norm
IDL outputs:
0.0000000 0.0000000 1.0000000
None.
ICY.REQ
ELLIPSES.REQ
Icy Version 1.0.0, 16JUN2003, EDW (JPL)
surface normal vector on an ellipsoid
