Having represented the CCTV industry for 20 years, it still astounds me why installers of video surveillance still do not understand the requirements to make a CCTV image useful. The above image is a good image but it does not meet the requirement.

Industry standards do exist but outside of government are seldom followed. They categorise CCTV into 4 main applications
1 – Observe - Generally observe/monitor behaviour within a broad area
2 – Detect - Verify an incident after an alarm or report
3 – Recognise - Monitor/track an individual person, object or vehicle
4 – Identify - Capture enough detail to identify a person, object or vehicle

For most installations, people are installing cameras that meet either 1 or 2 above, when they actually wanted 3 or 4.

In the image above, it would be classed as a type 3 - Recognise, which means if you know the person you could recognise them but if they are unknown you could not use it as strong evidence in locating the person.
The image should be a type 4 - Identify, in which case the scene should be much tighter. We call this quality 1-ICU (often remembered as 'I see you') The height of the image should be that of an average person and this will result in their face occupying 15% of the scene, which will give 88 pixels across on a 4CIF image.
Many other factors also need to be considered in this calculation but assuming everything was recorded at 4CIF this is the basics

In the above image, the face only occupies 6% of the scene. Less than half what is recommended for ID quality, which I am sure the ATM owners were believing they had.

The solution?
In most systems we design at IndigoVision, before we even look at the camera positions we ask "what is the purpose of this camera?" In most cases it it to identify but the client also wants an overview of the surrounding area. This is actually 2 purposes. A type 4 and a type 1or 2.
The reality is 1 camera, 1 application. So in many situations, we need 2 or more cameras. 1 watching a specific point or a door way where the person must pass and a second for the overview. This obviously has a cost associated and is sometimes perceived as a salesman trying to make more money but when it comes down to it, if you can not identify and convict due a to poorly designed CCTV system, why have one at all.

Tim Norton

05 Feb 2010 01:40PM nortont