Intrusion sensors are widely used in security systems to monitor the boundaries of a well defined area in order to detect the presence, location and motion of people and vehicles. Exemplary sites that may benefit from the use of such security systems are national borders, boundaries of military installations, nuclear power plants, prisons, and businesses. A number of existing intrusion sensors based on seismic, ultrasonic, infrared, and magnetic technologies have been employed, but are unfavorable for numerous reasons. These existing systems are expensive, difficult to conceal, have high false alarm rates, and are capable of providing coverage for only a limited portion of a perimeter.
By way of illustration, in the particular application of intrusion sensing to the monitoring of national borders to detect and apprehend illegal drug smugglers or illegal aliens, the border terrain under surveillance may be vast and rugged. The sensor system employed in this application must not only detect an intrusion but must also be able to determine the location of the intrusion along the monitored border. The sensor system must also be easily concealable to prevent tampering. Furthermore, such a system must have and maintain a record of low false alarms. Conventional intrusion sensing systems are not able to meet such stringent requirements or cannot provide satisfactory performance without incurring prohibitive costs.
Accordingly, it is desirable to provide an intrusion sensing system which provides intrusion detection as well as the location of intrustion. It is further desirable that such sensing system be deployable in a reasonable manner over a vast area, such as for the purpose of monitoring a national border.