A disclosed detector estimates the wireless terminal as being indoors or outdoors by utilizing information that includes measurement report data from previous calls involving both i) wireless terminals that are known to have been indoors and ii) wireless terminals that are known to have been outdoors while the measurement report data was collected. Based on this call data, one or more classification features are computed in accordance with the illustrative embodiment of the present invention. Then, for a wireless terminal that is to be classified during a call and with respect to the terminal being either indoors or outdoors, features that are representative of that wireless terminal for the call are evaluated against a characterization that is a composite of one or more previously-computed classification features. The features that are representative of the wireless terminal can be derived from the measurement reports received from the wireless terminal during the call.