CCTV (Closed Circuit Television)
Camera Surveillance
As the very presence of a CCTV camera is known to make people feel safer and act as a deterrent to would-be vandals and criminals, it is not surprising that the use of CCTV is becoming ever more widespread.
In the United Kingdom alone, there are approximately 2.5 million CCTV installations watching everything - cash machines, public transport, town centres, retailers, schools and the workplace to name but few and not to mention private installations to protect an individual’s property and possessions. CCTV footage can also act as evidence in the event of an incident and help convict troublemakers and thieves.
But in at least 75% of all cases where Police use CCTV as evidence in court, it is found to be inadmissible as the images recorded are of such a poor quality or the target person is far too small to be recognised. There are a few rules of thumb that are used to judge how good a recording would be:
To detect a person, the image of an average person should be approximately 10% of the screen height.
To recognise a known person, the image of an average person should be approximately 50% of the screen height.
To identify an unknown person, the image of an average person should be approximately 120% of the screen height (approximately from the knees to the top of the head)
These guidelines are issued by the PSDB (Police Scientific Development Branch).
Consideration should be given to the impact that the Data Protection Act 1998 has on the use of CCTV and to ensure that, where necessary, the requirements of the Act are met. There are eight principles that apply to the use of CCTV. These include signage, which should clearly state who is responsible for the system and how to contact them. Systems must be accurate and properly maintained to ensure that the data is accurate, not excessive or kept for longer than is required. Recordings must not made available to people who have no right to it. The only people who should see the CCTV images are those who are needed to fulfil the purpose of the CCTV system.
As with most things, CCTV can be as simple or as complex as the occasion demands. Many factors have to be taken into account when producing a technical specification – among them, the aspirations for the system and the physical constraints of the site, as well as the use of the right equipment,
There is an ever-increasing wealth of equipment available - cameras for night vision and low light, vandal resistant and bullet resistant cameras, cameras for covert and overt operation, among others. Light levels, different types of light, direction of light, resolution and pixels, auto exposure control and sensor size are also part of the camera equation.
The camera lens function and mounting must be specified with care to ensure that it is appropriate for the application and will provide the required image. The lens and mounting must also take account of the type of light used for the system (infra-red sensitive, for example).
If you do not choose the correct combination of all these items, the results produced will never be as good as they should be.
Monitors, like cameras, can be monochrome or colour. However, size does matter; if a multiple camera display is required, a screen of not less than 17” is needed to display up to 16 pictures.
There is hot debate over the choice of recording equipment – analogue versus digital – but the key to successful video recording is a combination of the right conditions, the correct equipment and proper maintenance of the system.
If using a Video Cassette Recorder (VCR) for example, the correct tapes must be used, (not the cheep type available in the market). The VCR should also be serviced every year, although it is worth mentioning that it is generally more cost effective to replace the VCR than to have it serviced. The throw- away society is definitely here!
The traditional time lapse VCR has now largely been superseded by the digital Hard Disk Recorder (HDR). The HDR stores the images on to a hard disk drive. It does not wear out; the quality of the image is superior and searching for an incident is easily achieved by time and date. The size of the hard disk must be big enough to retain the images for as long as they are required in line with the aspirations for the system.
Careful consideration should be given to specific decisions relating to recording. These include the number of frames per second required per camera (some cameras may have different requirements for this than others); the image quality required to record per camera, and whether any alarm triggers are needed to identify movement in the view of some or all cameras and, if triggered, whether the frame rate should change.
Finally, consideration must be given to the housing for the equipment. Not only should it be suitable for the environment, but also for ease of installation and future maintenance.
To be confident that the equipment can be maintained by the company who carried out the installation, or by a different company appointed to carry out maintenance, proprietary equipment should be avoided where possible.
It is now possible to monitor CCTV systems remotely by plugging cameras directly into a digital video transmission unit installed in a remote site. The transmission unit compresses and transmits video signals through regular telephone lines, ISDN/ADSL, and viewing software installed on a PC provides system control allowing the user to monitor incoming videos from a remote site. This service can also be provided by a monitoring centre, ensuring that activity on a site is responded to appropriately.
Reactive CCTV monitoring involves alarm detection on site which initiates a picture transmission to the monitoring centre. Depending on the requirements and the situation, the alarm is acted upon by the monitoring centre.
Proactive monitoring (such as monitoring city centres or high street locations) is in real time. An operator constantly reviews the location and informs security or the emergency services of dangerous situations.
Both types of monitoring provide recorded evidence of what was seen which can be used to assist the Police in their enquiries. Historical evidence can also be used to supplement non-related incidents, enabling Police to build a case.
With so much to be taken into consideration, it is usually no longer adequate to install a DIY CCTV system particularly as some of these DIY CCTV systems can be illegal if they are incorrectly installed.
The “least cost” option will probably result in a specification of equipment that delivers very different images to those that expected and needed.
A designer and installer who has achieved NSI NACOSS Gold for CCTV offers a quality assured service by professionals who are fully conversant with the requirements of the Data Protection Act and knowledgeable about developments in technology.
Their experience with lens optics and camera technology will guarantee a satisfactory system and will often provide “added value” benefits by building a unique relationship with their client to provide an ongoing managed solution of their CCTV needs.
The Code of Practice is available for you to view at www.dataprotection.gov.uk