A Test for Admissibility for Two-Dimensional, Continuous Fields on
Planar Surfaces<P>

Wolfgang Heil<P>

Radar scatterometers on oceanic satellites provide wind stress data
over the oceans except for a $180^{\circ}$ ambiguity in direction.
Data sets consist of sticks, $2$-dimensional vectors of known
amplitude and direction but undetermined orientation.  In [2] it was
shown that, for admissible stick fields, the assignment of an
orientation to a single stick determines a unique realization of a
vector field from the given continuous stick field.  In this note a
criterion for determining admissibility of a given continuous stick
field is given.  This criterion depends only on the boundary curves of
the region on which the stick field is given and it can be effectively
checked.