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 CCTV Operational Requirements Manual 2009 recommendations

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 CCTV Operational Requirements Manual 2009 recommendations

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 CCTV Operational Requirements Manual 2009 recommendations

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CCTV Operational Requirements Manual 2009 developed by Home Office Scientific Development Branch establishes as a criterion a part of frame height occupied by a person of average height (1,64m - 1,76m or 5’4” -5’8”):

 

Monitor and Control - 5%;

A figure occupies at least 5% of the screen height and the scene portrayed is not unduly cluttered. From this level of detail an observer should be able to monitor the number, direction and speed of movement of people across a wide area, providing their presence is known to him; i.e. they do not have to be searched for.

 

Detect - 10%;

The figure now occupies at least 10% of the available screen height. After an alert an observer would be able to search the display screens and ascertain with a high degree of certainty whether or not a person is present.

 

Observe - 25%;

A figure should occupy between 25% and 30% of the screen height. At this scale, some characteristic details of the individual, such as distinctive clothing, can be seen, whilst the view remains sufficiently wide to allow some activity surrounding an incident to be monitored.

 

Recognize - 50%;

When the figure occupies at least 50% of screen height viewers can say with a high degree of certainty whether or not an individual shown is the same as someone they have seen before.

 

Identify - 100%

With the figure now occupying at least 100% of the screen height, picture quality and detail should be sufficient to enable the identity of an individual to be established beyond reasonable doubt.

 

This criterion is directly applicable only to analog video, therefore the document establishes rules how to use this criterion for digital images with progressive scan.

Vertical number of pixels of analog image with interlace scan is assumed equal to 400 pixels. Then the criterion is transformed to other resolutions by the relation of the number of vertical pixels to 400.

 

 

Let's transform this criterion to pixel/meter and pixel/foot for digital images, assuming that the person's height =1,64m (5'4"):

 

Monitor and Control - 5%*400/1.64=12 pixel/meter (4 pixel/foot);

 

Detect - 10%*400/1.64=24 pixel/meter (7 pixel/foot);

 

Observe - 25%*400/1.64=61 pixel/meter (19 pixel/foot);

 

Recognise - 50%*400/1.64=122 pixel/meter (37 pixel/foot);

 

Identify - 100%*400/1.64=244 pixel/meter (74 pixel/foot).