By Craig Donald.
Imaging technologies are increasingly part of the frontline for security, policing, warfare, and even areas such as fire management, border control, and building management.
These technologies include the traditional areas of CCTV and x-ray screening; however the use of electromagnetic spectrums is opening up new ways of looking at the world around us. This includes measures of infrared, thermal, millimetre wave and terahertz technologies portraying scenes in a very different form from what we see with the naked eye.
Even in areas such as CCTV, filtering techniques and computer representations are making the traditional viewing of these kinds of images more abstract. Further, we are increasingly likely to see the integrated use of these technologies in a specific location, or alternatively see them spread over a number of control points to evaluate risks in different ways.
The electronic imaging of people, goods, materials, areas, and even processes and movement is a fast developing aspect of how we monitor against a wide range of risks.
Imaging technologies can now create visual images on monitors or screens that are representations or abstract conceptualisations. For instance, the use of an electromagnetic wavelength is not measuring visible light, but rather differences in the emissions of particles. Similar issues with filters have been observed for low dosage full body scanners.
Moving to the further abstraction of a terahertz based system provides a general body shape reflecting blobs of various wavelengths of electromagnetic radiation while millimetre wave images also require a high degree of abstraction.
With this type of technology, the images being viewed are abstract, and the way in which they are displayed and the colours used are a representation rather than actual colour. In some cases, images are entirely synthetic – real items are being displayed in a representative form which may depart radically from the actual outline, shape, texture, surface composition, and form of the actual object.
This means that operators or people responsible for viewing image material are having to think of threat characteristics in conceptual rather terms. They are using abstract representations of a threat or risk for detection purposes rather than the normal manner in which humans see the world.
In terms of CCTV, we find for instance that using thermal cameras will allow the camera to view a scene or situation shrouded in darkness or mist, providing a very different image to the real life picture produce by a standard CCTV camera. Recognising body language takes on a new perspective under such conditions.
In military applications, the use of thermal imaging night vision goggles adds issues of depth perception as users learn how heat may impact within a three dimensional setting and what happens when you put your foot down in a particular hue of green or grey. These visual demands create a whole different set of recognition criteria and visual analysis techniques for effective monitoring performance.
Similarly, we have found with x-rays that aviation x-ray providers have reduced the possible number of filters available for x-ray screeners because of the increased choice results in prolonged viewing, which often leads to more confusion rather than improving decision resolution.
Technology developers need to give particular attention to the nature of the display and how to make it meaningful to operators. Not to do so would cripple the technology before it even starts. However, this is not always to say that the image representations are the best suited for people or even particular detection tasks or situations.
In addition, computer based visual analytic techniques are often added to the technology to assist in the detection task. This doesn’t always work to the specified level, and in some cases has been shown to detract from detection with more complex images.
