Home' RTCA Documents for Review : DO-230H FRAC Contents 155
©2017 RTCA, Inc.
Any ungrounded metal object in the vicinity of an electric field sensor that can change potential
can cause a nuisance alarm.
Weather-related sources of nuisance alarms include rain, as well as wet or melting snow.
Small animals that touch the wires and larger animals that approach the wires may cause alarms.
Wet plants or wet weeds that touch the wires can also cause alarms.
Because this sensor is a volumetric sensor, large moving metal objects near the sensor can cause
The performance test must confirm that penetrations or attempted penetrations of the wire array
that forms the electric field sensor system are detected at the required level.
To ensure the overall effectiveness of an electric field system, performance testing should
incorporate the use of a combination of common defeat methodologies (crawling, walking,
jumping, climbing, and bridging) applicable to an electric field system within each detection zone.
Each sector should be tested 30 times at points along the length of the electric field detection zone.
Video Motion Detection
General Characteristics – VMD systems analyze video received from cameras to detect changes in a scene
over time. Video (Image) Motion Detection (VMD) sensors use Closed Circuit Television (CCTV) systems
(Visual, Low Level Light, and Infrared) to provide both an intrusion detection capability, and a means for
security personnel to immediately and safely assess alarms. CCTV systems provide the added benefit of
documenting the events of an intrusion and the characteristics of the intruder.
Video Motion Detection sensors detect changes in the monitored area by comparing the “current”
scene with a pre-recorded “stable” scene of the area. Video Motion Detectors monitor the video
signal being transmitted from the camera. When a change in the signal is received, indicating a
change in the image composition caused by some sort of movement in the field of surveillance, an
alarm signal is generated, and the intrusion scene is displayed at the monitoring station.
Video motion detection (VMD) can be added to either analog or digital camera systems.
VMD requires the addition of hardware modules and/or alarm processing hardware and software.
VMD software can be downloaded into specifically configured digital cameras with embedded
digital signal processor (DSP) chips and memory so that the detection function occurs at the
Higher performing equipment employs sophisticated algorithms to detect and categorize a moving
target. VMD analysis algorithms are generally activated when movement occurs in the camera’s
field of view.
Users can calibrate the camera’s field of view with respect to object size for purposes of
classification, object type determination (human, vehicle), speed, size, direction, and location.
Range – Detection ranges are determined by camera type, chip size, lens focal length, pole height, look
down angle, object size and weather conditions. It is recommended to have at least 20 pixels on target for
accurate detection. Longer range coverage (3-400 meters) will likely require a camera field of view of 9
degrees or less in order to achieve sufficient pixels on target. When the camera is mounted on a 15ft pole,
this creates a donut hole blind spot around the pole of over 100 ft. radius requiring a second camera to cover
the blind spot.
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