void psv2pl_c ( ConstSpiceDouble point[3],
ConstSpiceDouble span1[3],
ConstSpiceDouble span2[3],
SpicePlane * plane )
Make a CSPICE plane from a point and two spanning vectors.
PLANES
GEOMETRY
MATH
PLANE
Variable I/O Description
  
point,
span1,
span2 I A point and two spanning vectors defining a plane.
plane O A CSPICE plane representing the plane.
point,
span1,
span2 are, respectively, a point and two spanning vectors
that define a geometric plane in threedimensional
space. The plane is the set of vectors
point + s * span1 + t * span2
where s and t are real numbers. The spanning
vectors span1 and span2 must be linearly
independent, but they need not be orthogonal or
unitized.
plane is a CSPICE plane that represents the geometric
plane defined by point, span1, and span2.
None.
1) If span1 and span2 are linearly dependent, then the vectors
point, span1, and span2 do not define a plane. The error
SPICE(DEGENERATECASE) is signaled.
None.
CSPICE geometry routines that deal with planes use the `plane'
data type to represent input and output planes. This data type
makes the subroutine interfaces simpler and more uniform.
The CSPICE routines that produce CSPICE planes from data that
define a plane are:
nvc2pl_c ( Normal vector and constant to plane )
nvp2pl_c ( Normal vector and point to plane )
psv2pl_c ( Point and spanning vectors to plane )
The CSPICE routines that convert CSPICE planes to data that
define a plane are:
pl2nvc_c ( Plane to normal vector and constant )
pl2nvp_c ( Plane to normal vector and point )
pl2psv_c ( Plane to point and spanning vectors )
Any of these last three routines may be used to convert this
routine's output, plane, to another representation of a
geometric plane.
1) Project a vector v orthogonally onto a plane defined by
point, span1, and span2. proj is the projection we want; it
is the closest vector in the plane to v.
psv2pl_c ( point, span1, span2, &plane );
vprjp_c ( v, &plane, proj );
2) Find the plane determined by a spacecraft's position vector
relative to a central body and the spacecraft's velocity
vector. We assume that all vectors are given in the same
coordinate system.
/.
pos is the spacecraft's position, relative to
the central body. vel is the spacecraft's velocity
vector. pos is a point (vector, if you like) in
the orbit plane, and it is also one of the spanning
vectors of the plane.
./
psv2pl_c ( pos, pos, vel, &plane );
None.
[1] `Calculus and Analytic Geometry', Thomas and Finney.
N.J. Bachman (JPL)
CSPICE Version 1.0.0, 05MAR1999 (NJB)
point and spanning vectors to plane
