Perimeter protection has always been an essential element at high risk sites, or where large and open boundaries exist. This particular approach to security has always included a wide range of options, such as fence-mounting sensors, buried detection systems, active and passive external detection and physical measures. Recently the options have expanded, with thermal imaging and video analytics offering tools when security perimeters require protection.
Whilst video analytics and thermal imaging are often mentioned in the same breath, the two technologies take different approaches. However, for many, their purpose is the same: detection! Often, where additional or follow-up surveillance is required, traditional surveillance systems should be used to complement either cameras used for video analytics, or thermal imagers used for the detection of heat sources.
Adding intelligence
Video analytics, especially systems that are certificated in line with i-LIDS datasets, use traditional video to detect exceptions in a wide range of applications. One specific data set – sterile zones – is ideal for use with regard to perimeter intruder detection systems.
A sterile zone consists of some form of obvious demarcation between an area that people are permitted to be in, and an area which they clearly excluded from. The idea of a sterile zone is not to physically restrict access to an area – although some sterile zones do just that – but to ensure that anyone entering the zone has done so with intent rather than accidentally. Typical approaches include fencing or other barriers, signage or audio-visual devices.
By creating a sterile zone, this establishes that any activity in the area represents a violation, and this fact alone simplifies the creation of analytics rules, which in turn ensures that the performance of the analytics engine is optimised.
It is the simplicity of the sterile zone, the ease with which a rule can be created when any presence is an exception, which makes it so effective when compared to scenarios with a greater number of variables. If someone is in the sterile zone, it is an alarm condition. The analytics engine simply needs to identify when any person is present.
To ensure that control room operators do not miss suspicious events, the role of video analytics systems is being increasingly emphasised when protecting a perimeter. To ensure the development of effective video analytics systems, the CPNI (Centre for the Protection of National Infrastructure) has worked with the Home Office to create the image library for intelligent detection systems (i-LIDS) datasets. These allow manufacturers to self-test the performance of video analytic solutions.
Best practice dictates that where video analytics is used to protect a sterile zone perimeter application, different cameras should be used for detection and for general surveillance. The latter can then be used to follow up any detections without affecting the overall performance of the analytics element of the solution. Also, it might be the case that the best positioning for cameras monitoring a perimeter is not ideal for any additional surveillance. By trying to cover both requirements, some degree of compromise might be introduced, and in many applications that simply will not be acceptable!
The thermal issue
Thermal imaging has been promoted as a perimeter protection tool, and that – along with economies of scale driven by other sectors – has put the technology firmly on the agenda. It is true that devices do still carry a price premium, despite falling costs.
Thermal imagers can deliver long range detection, and operate in total darkness, fog, smoke, etc., as well as typical daylight situations. Thermal imaging is not reliant upon light, because its image is not an optical one. Instead, the imagers use thermography, detecting the emission of radiation from objects. All objects over absolute zero emit electromagnetic radiation at differing levels, dependent upon their temperature. This radiation is what forms the thermal image.
Thermal imaging offers a wide range of benefits, and is also cost-effective. It’s not a low cost technology, but if employed correctly, and if understood by the integrator and the end user, it can represent value for money.
To appreciate the benefits of thermal imaging, it is important to stop thinking about visual information, and to start thinking about heat. For example, a living being will typically generate more heat than an ambient location. A vehicle that has recently been driven will generate more heat than one which has been parked for some period of time. Even events which have occurred previously can leave a thermal imprint. For example, a heavy item being dragged creates friction, which in turn generates heat.
Thermal imagers aimed at the security market have less adjustability than higher spec units for other uses, and as they are uncooled they usually work best when there is a significant differential in temperatures. This makes them simple to deploy, but does rule out some of the more intelligent uses that other industries take advantage of.
However, when you start to consider large or open sites, protecting the perimeter with thermal imagers does make sense. If an intruder conceals themselves in bushes or undergrowth, traditional video surveillance cannot detect them. Also, if an external detection system generates an alarm, the system operator can be at a loss as to what has caused it. Even where video surveillance is linked to the detection device, environmental conditions might make it difficult to ascertain the cause.
Benchmark ran a series of assessments with thermal imagers. What was interesting was that when the technology was first discussed with integrators and end users, they were excited by it. Then, on viewing the test images, their enthusiasm waned. However, once the technology was used to identify concealed intruders, verify alarms during hours of darkness, target tracking, etc., their enthusiasm quickly returned.
The reality is that the outputted images from a thermal imager are not high quality, and cannot be used for identification. However, when the technology is applied in perimeter applications, the benefits are obvious.
In summary
Both video analytics and thermal imaging can add an additional layer of protection to any perimeter-specific application. When used in conjunction with more traditional perimeter solutions, the degree of protection that can be realised is significant!
