Localizing an object with nger probes

We consider the problem of identifying one of a set of polygonal models in the plane using point probes and nger probes. In particular, we give strategies for using a minimum number of nger probes to determine a nite number of possible locations of an unknown interior point p in one of the models. A nger probe takes as input an interior point p of a polygon P and a direction , and it outputs the rst point of intersection of a ray emanating from p in direction with the boundary of P . We show that without a priori knowledge of what the models look like, no nite number of nger probes will su ce to localize the point p. When the models are given in advance, we give both batch and dynamic probing strategies for solving the problem. We consider both the case where the models are aligned rectilinear polygons and the case where the models are simple polygons.