Localizing an object with finger probes

We consider the problem of identifying one of a set of polygonal models in the plane using point probes and finger probes. In particular, we give strategies for using a minimum number of finger probes to determine a finite number of possible locations of an unknown interior point p in one of the models. A finger probe takes as input an interior point p of a polygon P and a direction Θ, and it outputs the first point of intersection of a ray emanating from p in direction Θ with the boundary of P. We show that without a priori knowledge of what the models look like, no finite number of finger probes will suffice 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.