The perimeter of a site is the ideal place for the first layer of security to be implemented. It represents the earliest point of detection and also allows the definition of private areas to ensure that intrusions beyond the boundaries are not unintentional. Given this, the emphasis on perimeter protection should be significantly higher in many applications.
The perimeter represents a very important element in any security plan. It is often the first point at which a demarkation between public and private land is made, and represents the earliest opportunity for a site to define when a target – whether welcome or not – has entered its space.
Whether a system is designed to detect intrusion or simply identify that the status of the area has changed, it is important that installers and integrators, and in turn end users, are aware of the need to have an identifiable and obvious perimeter. Whether this is a six foot fence festooned with razor wire or a simple low height wall which can be stepped over will be dependent upon the needs of each individual site. What is more important is that anyone entering a protected area is aware they have done so.
By creating an obvious barrier, it can then be considered that persons within the protected area have made a conscious decision to be there. It makes sense to also consider whether a perimeter can be adapted to enhance the security of the location. Due to the fact that it’s best practice to create an obvious perimeter, it makes sense to also use it for the first layer of a system.
For some, the term ‘perimeter protection’ summons up images of physical barriers. There is nothing wrong with a physical approach to perimeter protection, but such elements will not offer complete protection. These types of products work by making it too difficult or too time-consuming for criminals to effect an entry. The hope is that they’ll give up and move on a softer target.
To be more effective, physical measures will need to be used in conjunction with other systems. For example, a high wall can be scaled by a determined criminal, and once this has been achieved the site is obviously vulnerable unless the violation is reported by a monitoring system.
Given the depth of options, it makes sense to implement these either as part of a layered approach or linked with other systems to create a more holistic security solution.
Adding systems
Electronic perimeter security systems have often been considered to be the exclusive preserve of high-risk large and open sites. Lower risk applications are generally viewed as typical users of physical options. However, the evolution of technology coupled with economies of scale have resulted in the reduction of equipment costs. Additionally, the use of wireless connectivity has made installation and remote connectivity a realistic option for even low risk applications.
Despite these advances, some believe that the way to make a perimeter more secure is to have longer, higher, more robust physical elements. This is tied very much to a siege-mentality that seems to pervade thinking when it comes to perimeter security.
As already highlighted, if a criminal is prepared to put in the necessary effort, physical devices will be defeated. Technological solutions are far more credible and the argument for electronic perimeter security is ever more compelling.
This isn’t to say that physical elements at the perimeter do not have a role to play when looking at technology-based options. They can act to create a sterile zone: an area where the boundary is established and beyond which any intrusion can be deemed to be an event that requires some form of action.
Sterile zones are common element in many perimeter solutions because they simplify the generation of exception reports. If a sterile zone exists and all activity within it is prohibited, then any exceptions are clearly violations. This subsequently enhances the use of smarter technologies, because the solution starts with a simple premise that nothing should occur in the sterile zone.
It’s worth considering the end users’ goals when establishing which technologies to deploy in a perimeter system. In truth, this is usually a simple task. Most end users want to be informed of an intrusion as quickly as possible. Rather than delay intruders with obstacles that can be defeated in time, or capture video footage to be reviewed after the event, end users would rather take action.
A proactive design
There are many detection technologies designed to create an early warning. Detecting the presence of people before they can reach a protected area makes sense. However, in the past security industry standards relating to police response shifted the emphasis onto internal detection because of the increased stability such an approach offers.
Due to budgetary constraints and a lack of resources, police response to alarms has become somewhat hit and miss. The number of high profile cases where police did not respond, or where policies prevented a timely intervention, make it increasingly important for many end users that the earliest warning is achieved. This requires solutions delivering longer range detection, especially for applications on isolated industrial sites or in rural locations.
When it comes to detection over longer distances, there are a variety of options. Often the choice will come down to what the site requirements are and the physical characteristics of the protected area.
Choices can include passive detectors, active detectors, fence-mounted and other dedicated PIDS (perimeter intruder detection systems), video surveillance with analytics and thermal imaging with analytics.
Many manufacturers offer wireless versions of external detectors and these can simplify installation where cabling to a perimeter might be costly. Where advanced wireless connections are deployed, the stability is as good as hard-wired alternatives, but with the advantage of optimal siting of devices.
Passive detection predominantly makes use of PIRs. There are also a number of dual-tech and tri-tech units with a variety of coverage patterns and ranges. These devices use advanced signal processing to filter out sources of nuisance alarms, but there will inevitably be a degree of risk to stability in some harsh external locations.
Increasingly, installers and integrators are using passive detection devices in double-knock configurations. This often involves the detection device coupled with other detectors or video systems including analytics. This ensures that if an event occurs, it is only signalled as an alarm if both elements of the double-knock signal, either simultaneously or within a given time frame.
External passive detection devices can offer a cost-effective solution. There are many passive detectors with innovative dual sensor designs. These are predominantly aimed at shorter detection distances although a growing number can be used over extended ranges.
Photoelectric beams are well-established active detection devices and do enhance the level of reliability on offer thanks to ongoing development by the leading manufacturers. These work by protecting a straight line between points, usually following a perimeter. Unlike space detection devices they don’t cover open areas.
Over the years, photoelectric beams have undergone significant advances with regard to processing and stability. The days of wind-borne rubbish or small animals and birds triggering the units are over; and tamper and sabotage attempts have also been largely eliminated. The growth of longer range PIRs and combination technology space detectors has impacted on the appeal of photoelectric devices, but they still offer a reliable and effective perimeter-based tool.
As with passive detectors, active detector ranges vary, with distances into the hundreds of metres being achieveable. In Benchmark tests, many active infrared beams have exceeded their quoted ranges without any detriment to performance.
As is the case with passive detectors, active units can be linked with other technologies, or indeed with other detection devices, to create a double knock scenario.
Laser-based detection devices are another option and the choice of available devices is growing. One benefit of laser-based sensors is that there are units which can deliver exact positioning information.
While many detectors identify the area which is in alarm via zoning, laser sensors can pinpoint targets using X-Y coordinates. With appropriate software, this information can be used by the overall system to track targets around a site, adding to the useful data supplied in the case of an early warning system.
The video element
The use of analytics with both video and thermal cameras has allowed a more behaviour-based approach to be taken with regard to perimeter protection. When used in double-knock scenarios, the possibilities allow a high degree of filtering when deciding what constitutes alarm events.
As smart video technologies become more behavioural-based, this adds a high degree of integration between the perimeter and other systems deployed on a site. For example, laser-based detectors can deliver positional information to a VMS via a dedicated plug-in, which can then allow PTZ cameras to automatically track suspects as they move around a site. The same system could be utilised as a traffic management tool, for example, during periods when the site is open for business.
Linking traditional detection devices and smart video systems is a simple task as many VMS options allow rules to be created that link a wide range of inputs. The same can be achieved using smart intruder detection systems using recipes or scenarios to link numerous events such as detection alerts, site status conditions and video inputs.
Thermal imagers are becoming more affordable and offer a credible option for perimeter security, especially when linked with analytics.
In summary
Traditional perimeter protection systems were divided into passive and active detection, fence-mounted and buried systems. Nowadays the list also includes laser-based detection, video analytics and thermal imaging.
Developments continue to offer systems that are affordable and reliable, and add smart technologies for enhanced value. Despite this, too many still view perimeter solutions as a specialist option.
