THE PRINCIPLES OF PIDS
The first principle to “Demarcate” will clearly define the boundary of restricted areas. Visual demarcation will generally be the fence line itself; however, the fence needs to be identified with signage to make it quite clear that this is a secure perimeter and that breaching this fence line will incur a penalty. The penalty will be dependent on the nature of the activity or perceived intensions of the intruder.
Signage needs to be clear, concise and visible. Anybody approaching the perimeter, whether innocently or with an intension to breach it must be presented with a clear message that will define the purpose of the barrier and the severity of the consequences if they do breach it. Effective signage can also provide a level of deterrent that will discourage casual wandering into prohibited areas.
“Detection” is the process of identifying and notification of a valid intrusion event, or attempt. There are many technologies that can be deployed from vibration sensors to radar. A key point to remember when deploying any technology is the consideration of the local environment. Technology can be affected by terrain, weather conditions, wild life and vegetation, amongst many other factors.
Whenever possible it is better to “Deter” an intruder rather than detect the event. Signage and visual cues can be used to put off the less determined but the higher the motivation of the intruder the less likely they are to heed any warnings.
Security planting, such as thorny bushes can be used to deter people with a relatively low motivation to enter a particular area.
A highly motivated person will attempt to breach perimeter defenses whatever the risk. In this case “Delay” tactics need to be deployed to ensure that the perpetrator is caught and either detained or displaced. Delays can be caused by the physical strength of a barrier against intrusion or entanglement by something such as razor wire.
When designing a perimeter system of this magnitude it needs to be considered that there will be an element of nuisance alarms. These will be managed, to an extent, by the technology deployed. However, extreme weather conditions and animals will cause systems to trigger a “false” alarm condition. If the frequency of nuisance alarms gets above a certain point, operators become complacent and reset alarms without investigation. In order to maintain operator alertness it is essential to minimize events and provide a facility for them to be able to instantly verify or “Determine” the event as it happens.
One of the best forms of verification is visual by the operator. If the operator can see what has caused the event they are instantly armed with the best intelligence to react appropriately.
Visual verification of the event can be achieved using conventional CCTV, however it has its limitations. Darkness, fog and foliage can all limit the operational effectiveness of a CCTV system. Thermal imaging could be considered as a means to overcome these issues.
The final system is likely to be made up of a combination of techniques to protect the perimeter; using different delaying methods dependent on environment and sensitivity of the area. Nuisance alarms can be minimized by using dual detection methods so that if either detects an event it can alert the operator but not go in to full alarm until both detection systems register the same event.
Verification of an event can also be made semi or fully automatic by deploying specific software that analyses the content of a video signal to determine the nature of the intrusion before bringing it to the attention of an operator.