A locator according to various aspects of the present invention includes a receiver and a processor. The receiver receives several signals, each signal having respective indicia of identification device presence within a respective communication pattern. The processor performs a method for determining whether a first identification device is located within a zone. The method includes the following steps performed in any order. A first step of determining, in response to receiver signals, a respective reliability of communication between the receiver and a plurality of identification devices. The plurality includes the first identification device and at least one second identification device. A first and a second communication pattern each respectively has a periphery such that communication with a provided identification device when located beyond the periphery is less reliable than communication with the provided identification device when located within the periphery. The first identification device is located within the periphery of the first pattern. Each second identification device is located beyond the periphery of the first pattern and within the periphery of the second pattern. And, the first pattern has a periphery substantially within the zone. A second step of comparing each respective reliability of communication to a respective threshold to identify validly present identification devices. And, a third step of determining that the first identification device is within the zone in accordance with whether the first identification device is validly present within the first pattern, the second identification device is validly present within the second pattern, and the second identification device is not validly present within the first pattern.