utions will be
               inferior to their precision.

      SPICE_GF_MAXVRT

               is the maximum number of vertices that may be used
               to define the boundary of the specified instrument's
               field of view.

      SPICE_GF_MARGIN

               is a small positive number used to constrain the
               orientation of the boundary vectors of polygonal
               FOVs. Such FOVs must satisfy the following constraints:

                  1) The boundary vectors