The sheer proliferation of CCTV systems over the last decade or so has been little short of phenomenal. However, despite the myriad technical improvements in cameras, splitters and VCRs, the final image quality as recorded on tape is often unusable for identification or recognition by police investigators.
Therein lies the main reason behind the latest Metropolitan Police campaign, which comes in the wake of the BBC TV Centre car bombing in central London. Aimed at end users, the police are stressing the use of good quality tapes (changed on a daily basis), regular checks to ensure that times and dates are correct and that all tapes are kept for a minimum of 31 days after use. As the police rightly state, your CCTV system might not have been operating to the best of its ability…but the terrorist most certainly is.
From police experience, about 70% of tapes are completely unusable for identification purposes, while 20% are only of limited use. A mere 10% provide high quality, useful and useable images.
Such figures must be taken in context. For example, an incident might occur on the street outside a building that has CCTV coverage, but only where the cameras are positioned to identify people walking in and out of the building – not along the pavement. The images might well be unusable for evidential purposes, but not necessarily through failings in the CCTV system itself.
What is important for any CCTV installation is that it operates within its own design specifications. Those specifications are not cast in stone – over the years, a building or an environment can change in its pattern of use and by way of new building works, such that the CCTV specification will need constant review to take account of any such changes.
When called in by CCTV end users to carry out image quality audits, Dectel’s technicians regularly come across faults such as cameras pointing in the wrong direction, dirty camera housings and lenses, poorly-maintained VCRs and the use of inferior quality tapes.
Managing your CCTV system
There are two main factors that contribute to poor quality recordings: worn tapes and worn out recording heads. A procedure that ensures tapes are of suitable quality and are regularly renewed should be part of the normal management of a CCTV system. Similarly, VCRs should be maintained in accordance with the manufacturer’s recommendations – the recording head in the VCR rotates at high speed as it comes into contact with the magnetic tape, and constant use will gradually wear away both the tape and the tape head.
In terms of standard analogue video, degradation of the recorded image is almost imperceptible at first and, since it’s a gradual process, there’s no precise cut-off point between ‘acceptable image’ and ‘no image’.
Defining the audit trail
To ensure that CCTV systems are indeed operating to specification, regular image quality audits should be carried out (eg on a twice-yearly basis), preferably by an independent company that’s neither responsible for the system maintenance nor supplying the hardware.
A key question is to determine the main purpose of the CCTV system, which could vary from acting purely as a deterrent through to the identification of unknown individuals.
Equipment details are also important, such that the type of multiplexers, VCRs, cameras and tapes, etc used in the system can be taken into account when decisions are made.
Dectel’s quality audit covers critical issues relating to the camera, the VCR, the tape and the overall system environment. Results of the analysis can then be compared to the system’s stated requirements. The subsequent report should provide detailed recommendations so that the end user can take steps to rectify any failings that have been identified.
Above all, there must be a clear and authenticated audit trail to demonstrate to the judiciary that the videotape images in question are indeed what they purport to be. This latter requirement involves a complex but well-understood and accepted set of procedures designed to enable the prosecution to refute any objections from the defence about the validity of any video evidence.
Just like the BBC Television Centre bombers, criminals do not give advance notice of their crimes, so it stands to reason that any CCTV systems must operate – and rigidly adhere – to their specifications 24 hours a day, 365 days each year. Regular quality audits are the key.
John Ellis is joint managing director of Dectel Security
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