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Unblinking Eyes

Fixed wireless surveillance cameras can lower crime rates and make the people you serve safer...for a price.

December 29, 2009  |  by Tim Dees - Also by this author

Resolution and Bandwidth

The technology of the cameras themselves has been driven largely by the demand in the consumer market for higher resolutions and more light sensitivity for still and video cameras. Public safety reaps the benefit without a large investment in research and development because virtually every feature available on a surveillance camera can be had on consumer products available at Best Buy.

Standard closed-circuit television (CCTV) cameras don't produce video that is anything to get excited about. A color CCTV camera typically maxes out at 560 lines of resolution, or a little better than standard broadcast video (480 lines). Internet protocol (IP) based video cameras produce up to five megapixels of resolution, more information than you can see on an HD television display. But the high-resolution IP cameras are very expensive, and their output takes up a lot of bandwidth. For this reason, most surveillance cameras are CCTV.

In the movies, the good guy can tell a technician to "zoom and enhance" an area on a fuzzy surveillance video, and he'll get a clear shot of a license plate, the label of a package lying on the front seat of a car, or a portrait of the killer reflected in the chrome of a hubcap mounted on a car moving in the opposite direction at 60 mph. In reality, there are several limiting factors affecting the kind of images you can expect.

High-resolution images are available (if you can afford the hardware), but there's still the problem of bandwidth. Unless you just happen to have access to a fiber-optic network on the utility pole where your camera resides, you're probably going to have to rely on wireless data.

The most common wireless networks are variations of the Wi-Fi technology available on every laptop computer and at most coffee shops these days. How much data can be pumped through that connection is a function of the bandwidth of the hardwired node you're connecting to, how many other users are sharing that connection, and what they're sending or receiving. It's not much different than sharing water from a single pipeline. You're never going to get more than the capacity of that pipeline and most of the time you'll get a lot less.

Earlier this year, the FCC allocated the 4.9GHz frequency band exclusively for public safety use. This means that first-responder agencies do not have to share wireless data bandwidth with consumers and private sector users, providing they have the proper equipment and a license. The 4.9GHz frequency band can support, in theory, 54Mbps (a typical cable internet connection is around 5Mbps), so there's more capacity for the agencies that can buy the equipment and not saturate the band.

Depth of Field

Other factors that affect the images include focus and depth of field. When there's lots of light, cameras use small apertures (measured in f-stops like f5.6) and the zone where everything is in focus is larger. This in-focus zone is called the depth of field.

As light decreases, the camera has to open the aperture wider, and the depth of field decreases. Photo manipulation can resolve many problems with an image, but bad focus is very hard to correct. Any agency that is going to depend on a lot of video-based evidence to solve cases is well-advised to obtain a forensic video setup and train some officers in its use. A typical forensic video "lab" (consisting mostly of a powerful desktop computer and appropriate software) costs around $30,000, but can work miracles in the hands of a skilled technician.

Surveillance cameras can act as force multipliers, but the effectiveness of the cameras can also be multiplied by piggybacking them with audio surveillance systems that triangulate and pinpoint the location of gunshots in real time, and automated license plate recognition (ALPR) systems that passively record the license plates of every vehicle that passes within their view.

Citizen Concerns

For every citizen who praises and welcomes public safety surveillance systems, there seems to be at least one more who condemns the technology as an invasion of privacy.

George Orwell's novel "1984" predicted a totalitarian society where every public venue and virtually every room in private residences was dominated by a "telescreen" that constantly broadcast propaganda extolling "Big Brother" and vilifying whatever nation was opposing him.

The telescreen had a feature not found in real-world TVs-while you watched it, it watched you. Any behavior that appeared suspicious or subversive invited a rebuke from the person on the display or a visit from the universally feared Thought Police.

So long as police cameras aren't peering into windows or other areas where there is a reasonable expectation of privacy, organizations like the American Civil Liberties Union and the Electronic Privacy Information Center don't have a valid cause of action to prohibit them.

Still, Chicago and other cities have proposed laws requiring certain crime-prone businesses to install security cameras. Will these cameras eventually feed into public safety monitoring centers, and could someone raise a valid privacy concern because of it?

It's too soon to tell. Surveillance technologies are changing the street crime world, and maybe the legal world, too.

Tim Dees is a retired police officer and the former editor of two major law enforcement Websites. He can be reached at [email protected].


Cobham Ltd.

Comdesco Group


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