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Wide Area Surveillance

Background of Perimeter Protection - Fences and One-Dimensional Sensors

The history of perimeter protection is based on building fences. That basic concept evolved into detecting activity along the fences using a variety of sensors either integrated onto the fence or stand-alone sensors separate but aligned with the fence. Today a wide variety of fiber and wire-based sensors are available to mount on a fence, as well as many different
types of IR, radar, optical, seismic and acoustic sensors to place along the fence line. Generally some camera support is provided, with the cameras programmed to point to pre-set locations along the fence, depending on where an intrusion is being attempted.

This concept of fencing with one-dimensional sensing has some drawbacks. It provides no warning of an impending intrusion. If the intrusion occurs, it provides no information of the path the intruder takes or his current location to aid the response team. There may or may not be information on the number of intruders or their composition.

Wide Area Surveillance

A more robust perimeter protection would consist of sensors looking out beyond the fence in order to detect potential intruders in time to plan and initiate the appropriate response. It would track the intruders to determine their intention and their numbers. In addition, since a wide area sensor generally sweeps a 360-degree circle, it would provide continued tracking of the intrusion even after penetration of the perimeter, greatly enhancing the effectiveness and safety of the response team.

The Benefits of Radar-Based Surveillance

There are two primary technologies which have been used for wide area surveillance: radar and optical/infrared cameras. For security applications, cameras have been used for many years as the primary surveillance technology. However, they are not well suited for wide area surveillance, which requires rapid inspection of large areas to identify movement of small targets. It is possible for a camera with video motion detection to detect small moving targets, but only in the angle sector at which it is pointed. Wide area surveillance also requires extremely low false alarm rates, which is difficult for cameras
in a variety of lighting conditions. It can be said that using a camera to search a large area is like looking through a straw. However, cameras provide excellent target identification when pointed at the target.

However radar technology is inherently suited for wide area surveillance. It can quickly sweep a full 360 degrees, analyzing the return signals to determine if there is any movement in the area. It operates in all weather and lighting conditions, and can be designed to have an extremely low false alarm rate. It can work over land and water, and detect a variety of targets: i.e. crawling, walking and running people, vehicles, boats and swimmers. A radar can allow the exact location and path of travel of the target(s). A radar surveillance system can also provide masking of areas where detection is not required, in both range and angle, so that complex installations can be masked appropriately to avoid nuisance alarms from areas where activity is allowed.

Historically, radar technology has had several negatives: it has been difficult for security forces to operate, requiring excessive training and maintenance; it has been expensive; and it is usually unable to provide the operator with the classification of the target. That is because, until recently, radars have not been designed for security applications. Security radars are now available which search large areas quickly, have low false alarm rates, are simple to operate, detect even the slowest and smallest targets, can be networked for perimeter protection, and they are affordable.

A New Concept for Perimeter Protection

The new concept consists of using modern radar technology for wide area detection of objects which are moving, and then using the precise location information from the radar to point a camera at the object. The operator is then presented with the location, direction of travel and identification and number of potential intruders, all in a matter of seconds. This allows the operator, at his console, to quickly have the information he needs to determine an appropriate response. He can do this without having to constantly stare at a bank of monitors, since the radar will sound an alarm when an intruder is present. The benefits of this system are:

  1. Dual technology approach provides both wide area detection and tracking and positive identification of threats. At the same time it reduces nuisance alarms and provides redundancy.
  2. The system continues tracking the intruder with both radar and camera, even after a perimeter breach, to provide real time assistance to the response team. The operator can take control of the camera at any time to investigate other targets. In addition, multiple cameras can be assigned different targets.
  3. As noted above, the system allows for masking of unwanted areas. These masks can change at a pre-determined interval.
  4. The system can also be teamed with an IFF (Identification Friend or Foe) system so that intruders can be identified even in areas where activity is allowed, i.e., aircraft ramps. Targets identified as friendly by other means can also have their alarms suppressed.
  5. Communications between the radars and cameras and the control station can be either wired or wireless. Battery backup is provided for several hours of power outage. Operation is possible either in a fixed location, man-portable or mobile, or mounted in a vehicle or a trailer.