Perfect pixel count
Moving into IP
Selecting the appropriate surveillance camera to fulfill operational requirements has always been a challenge.
With the introduction of IP cameras, and especially the development of megapixel and HDTV cameras, the need has emerged for a new way of determining how to meet operational requirements. These six steps describe the Axis model for relating operational requirements to modern video and IP cameras.
When surveillance was all analog, selecting a camera to match an operational requirement was mostly about selecting the appropriate lens, as there weren’t many resolutions to choose from. To monitor people’s behavior, various requirements were established based on the height of a person in the scene. Whilst not an official standard, this nonetheless became quite a common way of setting the requirements for detection, recognition, and identification.
|Category||Operational requirement||Body height as percentage of image (4 CIF)|
|Identification||Sufficient detail to enable the identification of an individual beyond reasonable doubt.||100% from the UK source quoted – 150% also commonly used|
|Recognition||A high degree of certainty as to whether or not an individual has been seen previously.||50%|
|Detection||Determine with a high degree of certainty whether or not persons are present in the scene.||10%|
Even if the figures in Table 1 are good for standard analog resolutions, they pose challenges for the resolutions of IP cameras. Although it is possible to translate TV lines to pixels, (as in table 2), this is far too complex for real-life situations. Surely there must be a better way?