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DORI and digital cameras
With the whole multitude of CCTV cameras available today, BS EN 62676-4:2015 defines a means of understanding what clarity of image will be achieved by a particular camera with a particular lens. This quality can only be displayed if the display equipment meets or exceeds the quality of the camera/recording equipment.
When Blakeglow Systems are asked to provide CCTV images for specific needs we will detail on drawings what coverage we expect the camera we are quoting to provide. We use the DORI system to convey this information to our clients. Blakeglow Systems will always supply view line drawings for projects we win. Care should be taken when utilising video analytics as this can degrade the final image quality.
DORI– Detect Observe Recognise Inspect is defined in BS EN 62676-4:2015 as follows(PPM-Pixels Per Metre). Two further categories are defined by the standard – Monitor and Inspect – but they are not used here.
Detect – At this quality an operator will be able to determine a human or vehicle is there, or not (25 PPM).
Observe – At this quality characteristics of the viewed subject, such as clothing, car colour can be determined (63 PPM).
Recognise – At this quality it can be determined with a high degree of certainty if an individual is the same as someone they have seen before(125 PPM).
Identification – At this quality identification of an individual is beyond reasonable doubt(250 PPM).
In the below image we see the four DORI qualities mapped out for a CCTV camera monitoring a park. The requirement was for the observe category to be achieved throughout and the drawing showed the need for, in this case, another camera. The mapping gives an indication of how objects in the scene will affect the viewable area with the trees having a fairly significant affect.
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