Surveillance Monitoring Station Best PracticesBy John Honovich, Published Feb 03, 2011, 07:00pm EST
We examine key considerations in the design and use of video surveillance monitoring stations. All too often, the tendency is to hang multiple large monitors (42” or larger) on the wall, see how impressive it looks and be happy. Not only is that often not the best solution, it regularly wastes money and decreases the efficiency of surveillance monitoring.
Monitor Selection and Location
To avoid common mistakes, we recommend following 4 key principles in selecting and positioning monitors for watching video.
- Purchase surveillance-rated displays: End users are often tempted to purchase COTS displays, or in some cases, TV’s, instead of paying more for surveillance displays. What is typically lost when this happens are reliability and picture quality. Consumer displays are not designed to be turned on 24/7/365. As a result, their failure rate increases dramatically, sometimes lasting under a year. Consumer LCD’s also are prone to image retention or “sticking”, which is a phenomenon similar to burn-in of CRT’s, in which a faint outline of a previous image remains on the screen when the image changes. Menus and other GUI elements commonly stick. Surveillance displays are designed to run 24/7 without failure or image retention. We have seen too many end users purchase displays for their surveillance system at the local electronic store for $600, only to be dissatisfied in a matter of months. Expect to pay $1,500-3,000 for a professional-grade surveillance display.
- Ensure the right size images on the display: We recommend .5 to .75 inches tall for each foot of distance between the operator and the display. For example, an operator located 12’ away from a display should be viewing camera frames approximately 6” tall. On a 42” monitor, this equates to a 3x3 tile layout of nine cameras at that distance. Width will vary, given the different aspect ratios of SD and HD cameras. This also assumes full frame, and does not allow for image cropping or special views such as Axis’ corridor format. This ratio typically provides adequate detail to an operator so they may enlarge a camera view or send it to a spot monitor for further inspection.
- Avoid mounting these large displays too high. Many think the best monitor placement is up and out of the way, as monitors are very large and protrude from walls several inches. However, height increases the distance from the operator’s eye to the display, reducing the monitor’s usefulness, and forcing an operator to look above horizontal for extended periods of time results in discomfort, which reduces effectiveness. Monitors should ideally not be mounted above 15 degrees above level, based on the operator’s eye.
- Avoid too many displays: Following the guidelines for sizing images, if you end up with a video wall that causes any given operator to physically turn their head more than a few degrees from center to view them, the display is too large. Steps should be taken to create camera sequences to reduce the size of the required display, or reduce the number of cameras a single operator must watch and bring that display closer to them.
Determining Monitoring Approach
The more cameras you have, the less possible it becomes to monitor them all - even if that is all a person does. If you have more than 8 or 16 cameras, the probability of you missing significant events by simply looking at the screen is almost guaranteed.
Below we examine two main monitoring approaches: (1) proactive and (2) reactive. Almost all surveillance operations use a combination of the two depending on the role/significance of the camera. Best practice is to create “job descriptions” for each camera, as well as the system as a whole. These requirements should be reviewed with each operator, so they can understand the purpose of the system as a whole. These requirements can then be used to determine how you will monitor each camera - proactively or reactively.
Cameras Used Proactively
This category includes systems where an operator is actively watching video for any incidents as they happen. Many times this means active control of PTZ cameras. Proactive systems can often become burdensome to monitor due to limitations in how much video a human can actively view. Industry lore varies in respect to this topic, but common numbers cite between 12-24 cameras being monitored for somewhere between 15 minutes and two hours as being the human limit. We would tend to believe the lower side of both of these figures.
In systems such as these, most often the only option is to view the cameras on a large display or displays. If there are numerous cameras, responsibility for viewing is often divided amongst multiple operators, so Operator #1 watches only cameras from this area on monitor #1, and Operator #2 watches a different area on monitor #2. If there is not enough screen real estate available to view all cameras at once, camera sequences may be created. These sequences display one or more cameras in order, switching after a period of time. Most systems today allow for multiple-view sequences, so different four-by-four camera views may be shown in sequence instead of single cameras. Anecdotal evidence suggests that showing operators a random sequence of cameras improves monitoring performance, by removing some of the routine from the task.
Cameras Used Reactively
This category includes systems in which video is only monitored upon occurence of an event, either electronically or humanly generated. For instance, a door being forced open, or an analytic event, could trigger alerts on one or more cameras in the vicinity, attracting an operator’s attention. A dispatcher manning cameras only when a 911 call comes in is an example of a human-driven event.
Typically speaking, these systems may be monitored with much less screen space than proactive systems, as video does not need to be watched at all times. Two small monitors on the operator’s desk is a common setup for this monitoring style; one monitor used for multi-camera views, and another used to view the highest-priority or last-in event in full screen. This understandably decreases hardware and installation cost, since smaller monitors are less expensive, and multi-output video cards are not required.
Events used to drive video should be carefully selected, and reevaluated regularly. Used in conjunction with an access control system, for example, the surveillance system may pop up cameras upon a forced door alarm or an attempted use of a stolen credential. “Blue light” emergency phones, common on college campuses and in parking facilities, may trigger PTZ cameras to spin to preset positions up activation. Some schools are now issuing staff wireless panic buttons, which trigger recording and other events on the security system. And last but not least, however definitely most hotly debated, analytics may be used to call operator attention to specific events on specific cameras.
All of these are fine examples of ways to reduce the amount of video an operator must watch, but without maintenance and periodic evaluation, nuisance alarms may increase and monitoring staff will begin to ignore alarms, resulting in reduced system effectiveness. If an access controlled door’s request-to-exit PIR is malfunctioning, for example, forced door alarms may become routine, prompting the operator to ignore all alarms of that type. Analytics, if not properly evaluated and deployed, may produce repeated false positives, causing an operator to ignore the camera. It is therefore imperative that these integrations be maintained, as ignoring video increases risk and decreases ROI.
Most monitoring centers only have a single operator watching cameras. In this common case, the single best action to improve monitoring ease and performance, is connecting video to events whenever possible. No longer is the operator forced to stare at hours upon hours of video. Under normal operations, the guard could manually or automatically view sequences of cameras (aka video guard tour), with events drawing his or her attention from his routine. In single operator setups, avoid the multiple large display pitfall, as no single operator will ever be able to monitor that much video at once.
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