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

Wolfgang Heil

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.