Advanced Intrusion and Perimeter Detection

It is well known that most perimeter fences can be climbed, cut, torn down, or tunnelled under, regardless of their size and structure (steel, mesh, concrete, etc.). And unless you immediately know when someone has breached that perimeter, the fence is hardly more than a decoration.

read more

What is a Perimeter Protection System?

As the name suggests, a Perimeter Protection System (PPS) is a system consisting of sensors that detect an intruder whenever a fence or wall is climbed, cut, or broken and instantly notify the security guards that should take action in response. So a PPS refers to three main components: the Perimeter Fence, the Perimeter Intrusion Detection System (PIDS), and the Response Mechanism (security guards and procedures).

Focusing only on technology (PIDS), as a cost-saving alternative to good-quality fences, or having to employ security staff will always lead to an inappropriate PPS, regardless of which particular detection technology is installed.

Any proper design of a Perimeter Protection System should provide 5 basic functions ( 5D’s):

Deter (a mix of fences, lighting, visible sensors, and security TV cameras) – The objective is to deter the criminal from even attempting a breach of the system;

Detect (various sensors and technologies – mixed thermal and visible cameras are very effective as an accurate detection tool, and also provide situational awareness where intrusion was detected) – to monitor large areas of space and accurately and early detect, unauthorized intrusion, to get a fast and efficient response.

Deny (fences and gates, access control, checkpoints, etc) – The objective is to keep unauthorized persons out while allowing authorized persons to enter.

Delay (fences, locked gates, and other physical barriers) – The objective is to slow down an active intrusion enough to force the intruder to give up or allow the security team to respond;

Defend (the response mechanism- security guards or police) – is typically a security personnel response that attempts to apprehend the intruder. The response often includes the involvement of law enforcement.

How do the Perimeter Intrusion Detection Systems (PIDS) work?

PIDSs are based on the core principle of establishing a steady background state and continuously monitoring to detect any change above or below a predetermined threshold that indicates that an intrusion event has occurred. Any Perimeter Intrusion Detection System has basically  three important performance parameters to be considered:

The probability of detection (POD); The POD is determined by the sensitivity and design of the detection sensor, the environment, and also the quality of the actual installation itself. The experience, knowledge, and skills of the intruder also play a role.

The nuisance alarm rate (NAR); Nuisance alarms are intrusion alarms generated on the field sensor by non-intrusion events. The NAR is generally determined by environmental conditions such as wind, rain, vegetation, traffic, etc. but also by system sensitivity.

The vulnerability to defeat – typical measures used to defeat or bypass detection by the sensor;

An ideal perimeter intrusion detection system (PIDS) would simultaneously exhibit a 100 percent POD, a zero NAR, and be undefeatable, but typically there is a trade-off between the POD and the NAR – if you make the system more sensitive (a higher POD) then you will also see an increase in nuisance alarms.

Available technologies for PIDS

When evaluating any of the available PIDS technologies, we recommend paying attention to the following:

  1. maximum detection capability;
  2. ability to quickly and accurately pinpoint the location of intrusion;
  3. minimal nuisance alarms;
  4. system durability/reliability;
  5. minimal maintenance;
  6. ease of use and learning;
  7. ability to work with other existing and often complementary technologies.

Here are some of the technologies used in PIDS, available today on the market. We will get into details only for the most commonly used on the commercial market.

Table with technologies available today for commercial use

  • Fiber Optic (below a short description)
  • Vibration (below a short description)
  • Taut wire;
  • Strain Sensitive or Microphonic Cables (below a short description)
  • Electrostatic-field or Capacitive
  • Fiber Optics
  • Leaky Coax
  • Pressure Tubes
  • Geophones
  • Infrared (below a short description)
  • Microwave (below a short description)
  • Laser
  • Ground Based Radar
  • Visible Light and IR Video Analytics systems
  • Thermo-vision Analytics systems (below a short description)

Detailed description of technologies

Most PIDS are barrier-mounted, attached to a fence or wall, while some are ground-based or below-ground and do not require a physical barrier. What works best depends on your location and specific needs.


Fiber Optic Cable

Used on a fence, fiber optic cable is a precise perimeter intrusion detection system that uses light traveling down a glass fiber for transmission and detection. When someone attempts to climb the fence, the fiber optic cable vibrates, and the properties of the light traveling down it change. If this change in the light exceeds a predetermined threshold, then an alarm is flagged. Typically, the cable provides long-range coverage—up to 100 km per processing unit.

There are two main types of fiber optic intrusion detection systems: the traditional hardware-zoned systems and the newer, more sensitive interferometric systems that can also provide the actual location of an intrusion.

Application: The fiber optic cables are usually mounted directly to the fence fabric but could also be buried underground. When it is fence-mounted, a  good-quality and stable installation of the fence is necessary for reliable detection. For situational awareness, there is a need for an extra CCTV system.

Potential causes of nuisance alarms: Poor fence quality is the most common cause of nuisance alarms, along with improper installations.

Typical methods of defeat: Bridging or tunnelling will bypass the fence and, therefore, bypass the sensor.


Vibration (Rattler) Sensors

Fence vibration sensors are mounted directly on the fence fabric and will detect vibrations on the fence outside of an acceptable range, including those associated with cutting, climbing, or lifting of the fence. Vibration sensors can precisely locate an intruder. For situational awareness, there is also a need for an extra CCTV system.

Potential causes of nuisance alarms: As these sensors are installed on the fence, poor-quality fences with loose fabric will create too much background activity (flexing, sagging, swaying), initially generating nuisance alarms and eventually transmitting little reliable intrusion activity.

Typical methods of defeat: The most common defeat method is by carefully bridging (assisted climbing) the fence. An intruder with knowledge of the system may be able to climb the fence undetected. Although less common, tunneling or careful removal of fence fabric is always a possible defeat method.


Strain sensitive – Microphonic Cable

Strain-sensitive cables (also known as microphonic cables) consist of a sensing cable attached to the fence fabric, which is constantly monitored and will generate an alarm if an intruder attempts to bypass the sensor cable.

There are three main types of microphonic cables: coaxial, (uses a custom coaxial cable where the center conductor carries a permanent electrostatic charge); magnetic polymer or ceramic magnetic (uses two semicircular magnetic conductors separated by an air gap containing two uninsulated wires); and TDR ( uses a coaxial cable with two additional grooves containing sense wires).

Applications: Can be used on a range of fence types (up to 200 m/zone), but primarily galvanized chainlink and perimeter walls (to detect intruders breaking through the wall). Weldmesh, plastic-coated chainlink, palisade, and anti-climb fencing may give reduced sensitivity.

Weaknesses: Excessive heat, moisture, salt (marine environments), mishandling of cables in the field, and tight installation will dramatically reduce the sensitivity of the system. For situational awareness, there is also a need for an extra CCTV system.

Potential causes of nuisance alarms: Poor quality fence construction; tree branches; animals; adverse weather such as wind; rain and snow. In fact, anything that can cause the fence to vibrate or rattle can trigger the sensors; sensors running parallel to power cables or other sources of EMI, such as transformers, high-current switches, electric motors, or high-power cables, may cause interference and nuisance alarms.

Typical methods of defeat: As with most other fence-based sensors



Seismic Detectors

The system consists of multiple sensors buried underground and a processor that analyzes the acoustic signature of the event to identify an individual walking or a vehicle driving over the sensor. It has a high POD and low and few nuisance alarms if installed correctly.

Applications: Where covert detection is required and/or a fence would be unsuitable ( because no barrier is required and the system is underground (15-35 cm deep), it is virtually undetectable to the unsuspecting intruder). For situational awareness, there is also a need for an extra CCTV system.

Weaknesses: Sensitive to nearby pools of water, metal objects, electromagnetic interference, and passing traffic areas. A pretty expensive solution, as it requires extensive trenching and site preparation to ensure proper drainage. No deterrence.

Potential causes of nuisance alarms: Large animals, metal fences, signs, or other moving objects in the detection field; underground streams; flooding, nearby vehicles and pools of water. RFI and EMI emanate from sources such as electrical equipment, power generators, or electrical substations.

Typical methods of defeat: Deep tunneling, bridging, or, as the detection height is only about 1 meter, careful jumping. Can also be defeated by using wooden stilts.

Passive and Active infrared Sensors

Passive Infrared sensors (PIR) detect energy generated (infrared light coming from objects) within their field of view by external sources.  Any change in the „energy picture”  of PIR is interpreted as a movement by a person or animal and triggers an alarm.

Active Infrared Sensors  – require at least one transmitter and one receiver. The transmitter shoots out an invisible beam of infrared light aimed at the receiver. If nothing is in the way, the receiver “sees” the beam. However, if a person walks through or stands between them, they interrupt the beam and trigger an alarm.

Application:  Passive Infrared sensors are typically used to provide protection to specific outdoor areas, (typically 10-40m) in a multi-beam configuration.

Active infrared sensors are usually used in conjunction with a barrier fence that defines the perimeter to be covered. Active Sensor zone lengths can extend up to about 400 meters each but require a clear line of sight, clear of all obstacles that could block the IR signal. For situational awareness, there is also a need for an extra CCTV system.

Strengths: Relatively Low cost; Easy to deploy and maintain.

Potential causes of nuisance alarms: Imprecise alignment of the transmitter to the receiver, overgrown vegetation, stray animals, fog, heavy rain, snow, sand storms, moving objects, animals, birds, debris, movement of mounting posts, and severe temperature changes.

Typical methods of defeat: The most common method of defeat is bridging over or tunneling under the detection beams. As infrared detectors are line-of-sight devices, preventing blind spots where intruders can pass undetected is a must.


Microwave Sensors

Microwave sensors are mainly volumetric motion detection devices that flood an area with a high-frequency field and use radiolocation, similar to the echolocation used by bats. Any movement within this area disturbs this field (a change in the received frequency, known as the Doppler effect) and sets off an alarm. They can detect not only movement but direction and speed as well.

Similar to Infrared Sensors, there are two basic types of microwave sensors: monostatic sensors, which have the transmitter and receiver encased within a single housing to protect a well-defined detection zone, and bistatic sensors, where the transmitter and receiver are housed in separate units.

Application: Microwave sensors can be used to monitor an open area (monostatic sensors) or along the inside of a perimeter fence line or a sterile zone between two fences ( bistatic sensors typically used where multiple sensors are deployed).

Compared to infrared sensors, they’re more expensive and more prone to false alarms. But they’re capable of covering a larger area and are not susceptible to weather conditions.

Weaknesses: Potential for blind spots and reflections of nearby objects; sensitive to both EMI and RFI; not suitable for uneven terrain; requires power and communications to each device. For situational awareness, there is also a need for an extra CCTV system.

Potential causes of nuisance alarms: External sources of radio frequency interference from radio transmitters; EMI (electromagnetic interference from large electric motors or generators and power plants); moving objects and debris in the detection field, especially if windy conditions exist; movement of mounting posts the sensors are attached to; reflections off nearby metal or solid objects; pools of standing water (bistatic sensors).

Typical methods of defeat: Slow rate of movement through the field; crawling close to the transmitter or receiver; blind spots caused by uneven terrain, hollows, or shielding; tunneling beneath the protected area or bridging above the field.

Thermal Security Cameras with GPS and Analytics

In short, this method is one of the most cost-effective, and most powerful protection solutions for outdoor security. Rolf Control Access highly recommends it. Call us for more details!  

Thermal cameras with GPS and Analytics (ThCGPSA) allow users to precisely detect people, objects, and incidents in complete darkness and difficult conditions such as smoke, haze, dust, heavy rain/snow, and fog, with a high probability of detection and low nuisance alarms.

Incorporating global positioning system (GPS) location information into video analytics perimeter cameras provides a three-dimensional capability to ascertain the size, direction, and velocity of a moving object and obtain high performance and accuracy in detection. Also, this information can be used for situational awareness to accurately direct the guard’s response where the event is unfolding, in real-time.

So, ThCGPSA enables security staff to use them simultaneously for detection, observing, and monitoring intruders once they are detected. There is no need for an extra CCTV system anymore, which lowers the cost to install and maintain.

Adding the fact that these cameras can also cover large areas–up to 600m with high POD – results in even less hardware to install ( fewer sensors/cameras, and infrastructure) which means even lower costs.

Application: Not to be confused with video motion detection (VMD) systems, Infrared TV cameras, or „simple” video-analytics (tripwire, loitering, etc) solutions that have been in the market for many years, Thermal Cameras with GPS, and Analytics are more complex and an excellent solution for covering medium, but especially large and/or difficult areas.

Considering the reasonable costs of the overall solution, these cameras are also suitable for organizations with medium perimeter security requirements and average budgets for security.

Strengths and weaknesses: Very high POD and low NAR; easy to deploy and maintain at lower costs; Can often be integrated into the most popular VMSs on the market; Can cover large and difficult areas; It helps security staff track intruders even in no-light conditions or severe weather conditions; if properly installed, it is not affected by wind, lightning, precipitation, temperature, moving clouds, shadows, or vibrations. High reliability, successfully withstanding harsh environments.

However, correct camera positioning, the poles they are mounted on, and obstructions in the field of view are all factors to be considered. For instance, vegetation in the field of view must be eliminated or reduced to a point where it does not affect the probability of detection or performance of the system.

Potential causes of nuisance alarms: Possible large animals;

Typical methods of defeat: Blind spots within or moving beyond the camera’s field of view, only if improperly installed; physical attack on; blinding of the camera, if improperly installed.