School Camera Coverage Critiqued
In this update, we examine a December 2011 article from Campus Safety Magazine [link no longer available], intended to provide guidance in camera placement to K-12 facilities. Aside from the article essentially being a lightweight fluff piece, written by a manufacturer, we fundamentally disagree with many of the tips given.
Parking Lot Coverage
The first recommendation the article makes is placement of cameras in parking lots. Left at that, this is not a bad recommendation, as numerous incidents occur in parking lots, whether fights, vandalism, collosions, or others. However, it then goes on to state that "From high up on the rooftop of a school building, they [administrators] can zoom in and get a clear image of a license plate way across the parking lot. Plus, they can cover an entire campus from fewer locations." We find this flawed for two reasons:
- First, placing cameras at roof level on most buildings is not recommended, unless the camera will only be used for object detection. High angles provide more of a top-down view of the scene, which may result in more footage of the tops of heads and vehicles and less of faces and license plates. Cameras are typically best located as low as possible while being outside the reach of vandalism, usually 12-15 feet above ground.
- Second, covering an entire campus from a few locations will do little aside from provide a false sense of coverage. Historically, this notion is one of the most dangerous in the surveillance industry. Driven by a trained operator, PTZ cameras can provide more detailed recordings of subjects and incidents. However, even under manual control, they are still not seeing the rest of the scene outside of the current frame, which can and will result in missed incidents.
Unfortunately, there is no perfect solution for parking lot surveillance in many cases. Oftentimes, they are simply too large of an area to be covered with any sort of pixel density. Multi-megapixel cameras, while still unable to cover the entire scene in detail, will likely provide a better record of incidents than PTZ cameras on tour. Users should pay attention to where the chokepoints of the lot is, and target these areas, along with providing an overview of the area. In this way, vehicles and subjects can be followed on the overview through the scene to the choke point, where better resolution or a smaller field of view may provide identifying details.
The second recommendation we disagree with is this: "Where 360 degrees of viewing are preferred, such as in the central junction of four corridors, the PTZ cameras are placed. Individual hallways use fixed position cameras, which cost less." Again, placing a PTZ at the intersection of hallways is likely to provide nothing more than video that's worthwhile 25% of the time or less. With a PTZ camera on tour, looking down four hallways, missing incidents is nearly guaranteed.
A higher number of fixed cameras is a better option, though it will indeed likely be slightly more expensive, when installation labor, licensing, and the cost of the cameras are taken into account. In some locations, a 360-degree multi-imager camera, such as Arecont or Avigilon's offerings may be useful, as long as lighting levels are even, which interior hallways often are.
Finally, the piece goes on to state the benefits of day/night cameras, as such: "By being able to produce clear images in low light conditions, school districts save the expense of installing additional lighting."
As we have seen in our low-light tests, clear nighttime video is hardly guaranteed. What's worse is that camera features such as automatic gain control and slow shutter likely will produce brighter video, providing users with a false sense of security. Yes, the image will be brighter, but subjects will appear blurred if the exposure is set too long, and the gain control introduces additional noise into the image, adding up to video that is often useless. Ultimately, there are no tricks or tweaks that can replace decent lighting in exterior areas.
Live Operators Cannot Be Assumed
Taking all of the above into account, the biggest mistake in this piece is the assumption that live operators will be on available to control multiple PTZ cameras. As we discovered in our Fall 2011 survey, users are eliminating operators, making it unlikely that many small-to-mid-sized school districts would have operators available at all times. For this reason, two trends have developed:
- Higher numbers of fixed cameras are being installed, in order to cover more area, and/or more angles, with no operator intervention required.
- Sales of panoramic and multi-imager cameras have increased, in order to attempt to cover more ground with a single camera, still generally priced below the cost of a PTZ. Unfortunately, though, our tests have shown that neither of these options is yet ideal.