Page 8 - Security Today, March 2022

Reducing Nuisance Alarms Even a low rate of alarm can lead to complacency
By Tom Hofer
Critical infrastructure sites need reliable, cost-effective physical security solutions. For these solutions to be a success they must reliably detect and deter would-be intruders, en- hance intrusion assessment and response capabilities, secure remote and unmanned sites, and, finally, address one of the most prevalent issues with physical security, re- duce nuisance alarms.
NUISANCE ALARMS LEAD TO COMPLACENCY
Nuisance alarms are alarms that are generated when the site’s security system is functioning correctly but is being triggered by non-threat stimuli, which may include wind or other severe weather, nearby hu- man or animal activity, or wind-induced vegetation movement.
For operators, even a relatively low nuisance alarm rate (NAR) can lead to problems such as complacency–ignoring real alarms because it is assumed they are false–and increased costs for ongoing re- pair and maintenance.
SECURITY STARTS AT THE PERIMETER: FENCE SENSORS AND VIDEO ANALYTICS
Adding a perimeter intrusion detection system (PIDS), such as a fence-mounted sensor, augments the effectiveness of an existing fence by providing valuable ca- pabilities to detect and locate attempts to cut, climb or lift the fence.
Connected to the site’s alarm systems, PIDS can notify off-site security personnel of the intrusion and engage automated de- terrent mechanisms such as the strobing of lights at the fence line, increased illumina- tion of the overall site or using public ad- dress systems to provide audible warnings.
VIDEO ANALYTIC SOLUTIONS
Intrusion attempts can also be detected via video analytics by using either virtual tripwires defined along the fence or area masks. Entry-level analytics use simple mo- tion detection while more advanced analyt-
ics use sophisticated algorithms that detect and classify the presence of people, ve- hicles, and objects while rejecting environ- mental changes, including wind-induced movement, shadows and small animals.
Video analytics offer an exciting new set of capabilities that greatly enhance pe- rimeter security at relatively low cost:
• Supplement fence sensors by providing
additional detection capabilities (espe- cially important for low fences, orna- mental fences, and walls).
• Determine the direction of intrusions (ingress or egress).
• Provide covert detection (no visible equipment on fence).
• Detect and track people near both sides of the perimeter fences to provide early warning of potential security events be- fore they can occur. This early warning can be used to direct PTZ cameras, so that high-resolution video can be captured of the intruder at the time the alarm (from the fence sensor) is generated.
• Use anti-loitering analytics to detect per- sons “camped out” near the perimeter.
• Auto-track intruders with a PTZ camera af-
ter an alarm is generated (assists in assess- ment, response, and evidence collection).
A NEW APPROACH TO SENSOR FUSION: THE BEST OF BOTH WORLDS
Both fence-mounted sensors and video analytics are highly developed and mature technologies, but solutions that can fur- ther enhance public safety (and offer the potential to reduce operating and mainte- nance costs) warrant attention.
The concept of sensor fusion technol- ogy is not new. The basic premise of com- bining multiple sensors together to benefit from their strengths while eliminating their weaknesses has been discussed for many years. Historically, this meant a Boolean logic integration between two systems (typically a fence sensor and people track- ing video analytics, or a fence sensor and buried sensor installed in parallel).
This approach certainly can work to reduce nuisance alarms caused by well-
defined, predicted events.
A better approach is to introduce intel-
ligence into the sensor fusion system by synthesizing low-level data from the sepa- rate systems to generate actionable infor- mation. More than a simple Boolean logic integration, true sensor fusion analyzes real-time data alongside historical, loca- tional, environmental, and classification data before generating an alarm.
When signal response data is synthe- sized between sensors from fence video analytic systems, nuisance alarms generat- ed by wind or debris as well as non-threat human activity are virtually eliminated while maintaining the system’s high prob- ability of detection.
True sensor fusion has the following benefits:
• A lowest possible nuisance alarm rate leads to greater system confidence and better response times.
• Improved probability of detection (Pd), as the individual sensors can use higher sensitivity settings and announce distur- bance events faster.
• Simplified integration, as the alarm out- put arrives from a single source (sensor fusion engine).
While advances in perimeter intrusion detection and video analytic technologies will continue to offer exciting new capa- bilities, nuisance alarms will unfortunately remain an issue. Sensor fusion offers the means to defeat nuisance alarms while main- taining the highest probability of detection.
To take advantage of sensor fusion, electrical providers will need to work with security vendors that have the in-house ca- pability to intelligently synthesis low-level multi-sensor data in order to generate ac- tionable results. The resulting increase in system confidence enables security operators to focus on what’s impor-
tant, namely a quick and efficient response to real security threats.
Tom Hofer is the product manager at Senstar Corporation.
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MARCH 2022 | SECURITY TODAY
PERIMETER SECURITY