Countering ambiguity in exterior intrusion detection

Reliance on sensors for exterior intrusion detection is inherently uncertain because neither the occurrence nor the absence of an alarm has a unique cause. Does ldquoalarmrdquo status indicate that an intruder has been detected, or that current site conditions have satisfied the sensorpsilas alarm criteria, resulting in a nuisance alarm? Does ldquono alarmrdquo mean no intruder is present or non-detection of an intruder? The consequence is ambiguity in interpreting the alarm status of an intrusion detection system. Two formulations, consistent with Dempster-Shafer theory, are presented that assist the security operator in distinguishing detections from nuisance alarms each time an alarm occurs, and distinguishing no activity from non-detection in the absence of any alarm. The first representation fuses multiple values of probability of detection or nuisance alarm likelihood, while retaining the dependence on factors (e.g., weather, terrain, intruder activity) that influence detection capability and nuisance alarm occurrence. The second representation associates a level of belief for an alarm occurrence being a detection, a nuisance alarm, or a false alarm, or for the absence of an alarm indicating no intruder present versus non-detection of an intruder.