The Pursuit of Perfect Perimeter Protection
Intrusions into buildings, homes and other structures can be greatly reduced via the proper design and deployment of perimeter security measures. New developments and refinements in sensors, analytics and integration are helping to stop intruders in their tracks while averting false alarms.
If you asked 10 security industry professionals to define perimeter security, you would probably get 10 different answers. According to NFPA 730/731, perimeter protection is defined as “A scheme of protection that uses devices to detect intrusion at points of entry into a protected area such as doors, windows and skylights.” It is also further defined as “the physical limits of a property, which can be the exterior boundaries of premises or the walls, floor and ceiling of a building.”
Our first thought when making a security perimeter survey of a room or building is to think two-dimensionally and look at the surrounding openings or portals. Perimeter security should really be viewed as a three-dimensional threat and should include areas such as the ceiling and floor. An exterior perimeter security survey should include above and below the fence as well.
One thing can be said for certain: while physical perimeter security may be easy to define, the challenge of providing reliable electronic security and sensors for a particular physical perimeter remains technologically challenging. However, the integration of analytical video has improved the reliability of perimeter security.
Defining the 5 Objectives of Effective Perimeter Security
Any good plan or program needs to have strong objectives. What are the overall objectives of a good security perimeter? Let’s define them:
1. Deter — What deterrence has been provided? This may be a combination of physical security such as chain-link fencing, razor ribbon, signage, CCTV, lighting and guard patrols.
2. Detect — How is the intrusion being detected? This may be a combination of video, guard observation, dogs barking, explosion and electronic sensors. The earlier reliable detection can be accomplished, the better the chance of a positive response.
3. Delay — How much delay time is built into the security perimeter system? Will security personnel be able to respond in time to take action and assist in protecting the assets? Additional physical security barriers may be provided to extend this delay time.
4. Assess — The time period between detection and response. Exterior perimeter security systems are often very high in false alarms. How can security personnel verify the alarm is valid? Do the perimeter sensors call up a camera view and does that camera intelligently track the intruder? This could be technology such as visual verification from video, or a combination of technologies such as infrared and microwave.
5. Respond — The point at which a valid alarm has been determined by a qualified assessment, and security personnel respond. When activated, do the perimeter sensors provide a map and quick physical location of the intrusion alarm? If detection is not fast and accurate, the response time can be long enough for the detected intruder to escape.
Layering Approach Helps Catch Intruders, Lessen False Alarms
Once a possible intrusion is detected, the assessment phase takes place. The careful application of sensors that discriminate against false alarms can make life easier for the guard in a central command monitoring perimeter activity.
However, one must be cautious in applying sensors that have discrimination technology since too much can cause an alarm “miss.” When in doubt, it is always better to have an infrequent false alarm and catch an intruder than have a highly discriminating system that fails to detect that intruder.
Proper selection and mixing of sensor technologies is important. Good perimeter security should use what is referred to as the layering of various levels of physical security, such as walls, fences and gates, along with electronic security, such as access control, sensors and CCTV surveillance.
When applying sensor technology to the perimeter area around a building or a complex of buildings, it is very important to have a physical fence barrier. This will define the secured perimeter and prevent animals from falsely activating motion sensor technology. Even with a fenced and gated perimeter, securing the area from small animals and birds remains vexing. Also, one may need to secure exterior ladders on buildings and other high exterior structures such as public utility facilities. Motion sensing devices in these areas can have trouble with false alarms from birds.
Sparks, Nev.-based Protech manufactures a volumetric motion-sensing device specially designed for such applications. It uses a combination of technologies such as stereo doppler microwave and dual element detector technology.
Stereo doppler microwave sensors can determine the distance in inches (or millimeters) that a target must move to create a valid alarm signal. This allows a high level of discrimination against vibration and randomly moving objects (trees, bushes, blowing debris, swinging signs, etc.) as sources of nuisance alarms.
If security devices are to be mounted to security chain-link fencing, the fencing should be installed per the American Society for Testing Materials (ASTM) standard ASTM F 567. This will ensure a strong, steady perimeter barrier and reduce the chances for false alarms.
Ultra-Wideband Motion Detection Technology Offers Enhancements
New perimeter detection technologies such as ultra-wideband (UWB) promise new and exciting applications. UltraVision Security Systems Inc. of New Hampshire has designed the UltraSensor™ CMD2 (concealed motion detector), which can be installed behind reinforced concrete walls and floors, or buried underground and in roadbeds.
The UWB is a time domain electromagnetic transmission technology that has been used for decades in ground-penetrating radar applications. The reason for using a UWB signal instead of a single frequency transmitter (like microwave) is improved motion resolution, distance measurement and obstacle penetration.
Recent FCC rulings have allowed for the expanded commercial application of UWB technology. The flexibility of UltraSensor technology lends itself to being used in other UltraVision products, such as the LifeLocator™, a device that can be used by search and rescue personnel to detect people breathing under the rubble of a collapsed building.
Rather than just sending an alarm, the CMD2 can report the distance to the intruder, the intruder’s velocity and classify the target according to its mass: small animal, man, vehicle, etc. This allows for intelligent integration to other security systems.
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