Such objectives might be: prevention of theft, trespass, criminal damage, anti-social behaviour or many other crime-related activities. Maybe solutions are needed to help with the management of staff, the public, vehicles, licensing compliance, financial and public transactions, and alarm verification, to list just a few. Health and safety may be vital, including crowd management, life preservation (e.g. in swimming pools), lone worker protection, staff/public interfaces, or access control to secure areas.
Video surveillance resources
If CCTV is clearly the superior solution to achieve the objectives then the next stage is to decide what the system must do in order to satisfactorily meet those objectives. In CCTV jargon the must do factors are in the ‘Operational Requirement’ document. Put simply, this answers all key aspects of: why, where, what, when, how and who. More formally, this thinking process is detailed in the CCTV Operational Requirements Manual 2009, publication no. 28/09, by the Home Office Scientific Development Branch (since renamed CAST) which is recommended as a freely available 55-page downloadable PDF.
Let’s summarise some vital knowledge from it.
The ‘Level 1 Operational Requirement’ reflects the ‘why’ as clearly considered objectives, as outlined above, including: a statement of the problem; list of stakeholders; risk assessment; criteria for success; and the most effective solution decided upon.
The ‘Level 2 Operational Requirement’ requires drilling down into much greater detail, as follows:
The Rotakin’ CCTV test target in action
Since 1994 when the ground-breaking ‘Rotakin’ man-sized CCTV test target was introduced by the UK Home Office, the level of detail required in a CCTV image to meet its objectives has been well defined. Updated in 2009, these criteria are illustrated here using the 1.7 metre high target. Note that these figures are for PAL video from standard definition (SD) cameras which are still very widely used in 2012.
For Identification: the figure occupying 100% of screen height should be sufficient to enable identification of the individual beyond reasonable doubt.
For Recognition: the figure occupying 50% of screen height allows viewers to say with a high degree of certainty if the individual is someone they have seen before.
For Observation: the figure occupying 25% – 30% of screen height shows characteristic details such as clothing while also viewing surrounding activity.
For Detection: the figure occupying 10% of screen height enables a viewer responding to an alert to see with a high degree of certainty whether a person is present.
For Monitoring & Control: the figure occupying 5% of screen height enables a viewer to monitor the number, direction and speed of people across a wide area provided their presence is known.
It is important to note that the proliferation of High Definition (HD) cameras and multi-megapixel cameras does not change the thinking underlying these practical measures of image detail. For instance, identification using SD video needs the 1.7m figure at 100% (described above), but if using full-HD video with many more pixels from top to bottom the figure need only fill 38% of screen height to provide same level of detail, using straightforward pixels vs height calculations.
Returning to our opening statement, if you want your CCTV system to meet your objectives and provide a proper return on your investment, you need to start with an Operational Requirement, It is not rocket science and the benefits are enormous.
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