A brief Anti Terrorism informative for organisations using
Closed Circuit Television, potentially for "Homeland Security"
In the wake of the appalling terrorist outrage suffered by London on 7th July 2005, Doktor Jon would like to offer the following general advice, for any business or organisation currently using CCTV / IP or Network Video in the protection of their staff and premises.
Privately operated CCTV schemes can provide vital video recorded evidence, to support investigations following a terrorist incident. Many CCTV operators do not consider it their responsibility to ensure that any images captured by their systems, are going to be of any practical use. And yet historically, Doktor Jon is aware of at least one documented situation where poor quality CCTV images failed to prevent, a preventable terrorist attack.
If you are operating CCTV, at the very least please take the time to consider the following points; someone's life may well depend on it.
To achieve the very best quality from a CCTV security system isn't rocket science, but there are a number of common mistakes made, which if correctly addressed can make all the difference:-
1) Consider what the system is for? - In order to make the best use of CCTV equipment, you must define exactly what it's intended to achieve (perhaps have a look at the CCTV System Design section for more guidance). The golden rule is to try and optimise each piece of equipment to a specific defined task; in practice, multi tasking a CCTV camera generally means it doesn't do anything properly, so if you need to identify an individual or vehicle registration plate, make sure the camera is set up just for that.
2) Location of CCTV cameras - The vast majority of surveillance cameras are unfortunately not positioned in the ideal location. Installers are sometimes mistakenly required to place the cameras as close to the target area as possible, which is often not 'the way to go'. Imagine the camera is looking at the target through a one metre long tube. The trick is to fix the camera in a position where the smallest diameter tube can be used (in other words, all persons will ideally be moving within a narrow zone, usually towards the camera) - a technique which Doktor Jon loosely refers to as the "Cone of Containment". It is absolutely imperative that any suspect captured on CCTV, can be properly identified on recordings.
Also, be sure that any cameras mounted on the outside of buildings, are actually installed "lawfully" - at present, perhaps tens of thousands of cameras here in the U.K. ... are not!
3) Choice of lens - After inappropriate camera locations, the most common single mistake made is to fit the wrong lens on the camera. Many installations use wide angle lenses, which cover larger areas but do not generally provide recognisable images of suspects (at distance), for long enough on screen; unless of course, they are fitted to very high resolution MegaPixel IP ideo cameras.
Narrower angle 'Standard' or 'Telephoto' lenses fitted to cameras further away from the target area, are generally a much prefered option (info on lens coverages) - (working example of the "Cone of Containment").
Try and interprete exactly what is on screen for each camera - if there are large 'dead' areas of ceiling, wall, sky etc. the camera may need repositioning, a change of lens, or possibly even both, with possibly even a complete relocation to a more appropriate position.
Always make sure there is nothing obvious obscuring part or all of the area you need to watch.
4) Camera mounting - why oh why do installers insist on mounting CCTV cameras up with the gods.
Unless the camera is particularly prone to attack, indoor mountings should ideally not exceed 2.75 metres (or 9 feet) from the ground, and external units 4.25 m. (14 ft). Generally the higher you go, the less efficiently the camera performs.
5) Recording the pictures - If you are using an analogue Time Lapse Video recorder always try and set the recording speed to the shortest practical setting (normally 24 Hour) and restrict the maximum number of cameras connected through a multiplexer; the more cameras, and the longer the record setting, the bigger the time gap between recorded images. You can check the gap between recorded images by looking at the seconds display when playing back a recording (on playback, press "freeze frame" and then advance one image at a time using "frame advance" - simply count the number of images before the second display changes by one second).
If there are less than 2 -3 images per second consider making improvements to the record system.
If you are using a Digital Video Recorder (DVR) or Network Video Recorder (NVR), try and program the unit to its maximum recording quality (so highest resolution, minimum compression settings), with an absolute minimum record speed of perhaps 4 images per second (per camera - 7.5 ips or more is preferable - 12 ips would be considered most useful if there is insufficient disc space to accommodate real time recording ).
Likewise with a networked IP system, it is vital that any 'latency' problems do not affect the desired rate of image transfer, below an acceptable minimum number of images per second
It is much more important to record fewer high resolution images, than far more low resolution pictures - clarity is everything! (particularly in terms of forensic surveillance).
More important advice for CCTV operators >>>
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