Home News Thermal Imaging: The right temperature?

Thermal Imaging: The right temperature?

by Brian Sims

Hand-held thermal imagers can enhance the efficiency of manned guarding patrols on certain sites, and can also increase health and safety for those carrying out on-site checks. Many large campus-style applications or businesses with distributed sites make use of manned patrols, both during and outside of working hours. Patrols can be effective, both in terms of detecting and dealing with threats on the ground, as well as presenting a deterrent value. A manned presence can also deliver additional support services, such as assisting staff or visitors, and acting as a liaison between the business and the outside world. One area where the efficiency of manned patrols could be improved is with regard to their ability to assess all data should an incident occur, especially if environmental conditions are not favourable. Darkness, fog, rain and snow not only make it harder for manned patrols to assess what is occurring at any given time on a large site, but such conditions also present cover for criminals, whilst equally creating difficulties for legitimate on-site personnel or visitors. One common approach to enhance a manned patrol’s effectiveness and ability to gather and assess information is the use of video surveillance. With modern networked systems, video footage can be passed to a manned patrol via a mobile device, such as a PDA, a smartphone or a tablet. This adds benefits, but with one proviso: The viewed video must contain usable information. If there is insufficient light, or environmental conditions such as fog, rain or snow, then the video information might be of little use. This is more than simply an inconvenience. If, for example, an intruder is on site, individuals carrying out a manned patrol could be placing themselves in danger without any warning of what may be occurring. Also, gathered information would be limited to what could be seen and heard, which may not be very much at all. One alternative does exist, with regard to thermal imaging. Handheld devices are lightweight, easy to use, and deliver more than a simple indication that someone is there. They also ensure that site owners and managers can better meet their duty of care. Thermal signature The initial and most obvious use of a handheld thermal imager is to allow those on a manned patrol to see if anyone is on site. Although resolutions are low when considered against video footage, there will be enough information to identify any heat sources and to identify what they are, even over relatively long distances. Therefore, a member of a security or safety team can see if people are on site, how many of them there are, and can quickly identify if movement is being caused by something more innocuous, such as an animal. Even if people conceal themselves, thermography will identify them. To grasp the additional benefits of thermal imaging, it is important to stop thinking about visual information, and to start thinking about heat. For example, a vehicle that has recently been driven will generate more heat than one which has been parked for some period of time, thus allowing a guard to identify vehicles which have recently arrived, even if parked with a number of others. Events which have occurred previously can also leave a thermal imprint. For example, a heavy item being dragged creates friction, which in turn generates heat. Also, if a fire has started inside a structure, usually the first visual indication will be when the smoke or flames breach the building’s fabric. By such a point, a fire will have taken hold, and an early action is effectively ruled out. A thermal imager will allow more advanced notification of problems. The technology can be used to tackle situations that other solutions simply cannot address” concealed intruders, verification of alarm triggers during hours of darkness, target tracking, etc.. Whilst thermal imaging does not deliver sufficient detail to positively identify individuals, it does give some details that might not be expected. Many vehicles with sign-writing can be identified. This is because vinyl lettering has different thermal properties to those of the vehicle body. Many materials have differing levels of emissivity, and this difference can be seen in a thermal image. Indeed, the more you understand emissivity, the more you can appreciate the various applications for thermal imaging devices! Thermal technology delivers the ability to verify that an event has occurred (or is occurring), rather than identifying the culprit. However, care should be taken to consider operational ranges, which can be an issue given the way that thermal performance is quoted. Figures quoted for range might include claims for ‘detection’ and ‘identification’, and can cover hundreds of metres for handheld devices. It is very important to realise that these figures are based upon the Johnson Criteria, which was designed for military needs. Their definitions of detection and identification are very different to those of the security and safety markets! In a military action, it is vital to know if anyone is approaching. In the Johnson Criteria, the requirement for detection is just two pixels. All you need to know is that something, whatever it might be, is within a certain distance, so you can direct an ordnance strike. However, in a security or safety application, you don’t want to be generating an alarm event for a fox or rabbit! It is also worth remembering that thermal imagers cannot ‘see’ through glass. In summary Handheld thermal imagers deliver value-added benefits to manned patrols. The allow guards or safety personnel to quickly check for human activity, over long distances, in darkness, fog, rain, snow and even if a site is engulfed in smoke, making them very useful if an evacuation is taking place after a fire or other incident. They also ensure that those on patrol are aware of the presence of people in an area, and can act accordingly. This makes response to events simpler, whilst also enhancing the safety of the personnel involved. Economies of scale mean that handheld thermal devices are cost-effective, especially where the increase in personnel efficiency is achieved.

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