Reliable protection of unfenced objects by technical means: the impossible is possible!.
Rejecting progress is as absurd as rejecting the force of a fall. N. G. Chernyshevsky
The security systems market offers a wide range of perimeter security tools, but choosing the highest quality and most effective system that will meet specific requirements is not easy. When choosing a perimeter system, it is necessary to take into account many factors: terrain, presence and type of fencing, vegetation, distance to roads, power lines, etc.
Traditionally, perimeter security is provided by sensor systems, the operation of which is based on various physical principles. Usually, sensors are installed directly on the fence or in close proximity to it. When an intruder attempts to enter the facility, the sensor is triggered. However, how to protect a facility that does not have an engineering fence? The issue of protecting unfenced facilities using technical security equipment has remained virtually unsolved until recently.
To protect facilities that do not have a fence, it is necessary to create a so-called virtual perimeter — a ring in which security systems in real time will be able to detect and recognize intruders, moving the detection line hundreds of meters away from the protected facility. In this case, the security service will have a reserve of time to respond, receiving information about the appearance of intruders on the approaches to the facility.
Two-position radio beam sensors are widely used to protect unfenced perimeters. These systems consist of a microwave signal transmitter and receiver, which are placed at a distance of up to several hundred meters from each other. A sensitive zone with a cross-section of up to several meters is formed between the transmitter and receiver.
However, radio beam sensors are not always applicable. They can only be placed on flat perimeter sections where unevenness, grass height or snow cover do not exceed 30 cm. In addition, the relatively wide sensitivity zone does not allow the use of radio beam sensors on objects where people, vehicles, etc. may accidentally enter the detection zone. [1]
Sensor systems are intended to protect unfenced objects, but most experts argue that a fence is necessary in any case: «Securing unfenced areas is incorrect. In addition to a fence, regular lighting and a video camera are required for simplified monitoring and prompt response.» One false alarm per month is considered an excellent result of the operation of a security system for an unfenced object [2].
The problems of low reliability of alarms are solved in practice either by lowering the sensitivity threshold of the sensors or by installing several systems at the facility, the operating principle of which is based on different physical principles (for example, vibration-seismic systems together with infrared systems). In the first case, the sensors are triggered less often, but they can miss a real intruder when trying to enter the facility. In the second case, the probability of false alarms is reduced, but the lack of video information does not allow us to give a 100% guarantee. In addition, installing several security systems is not profitable from an economic point of view.
Perimeter security systems must meet general requirements:
the ability to detect an intruder on the approaches to the facility and when trying to enter the facility;
no «blind» zones;
24/7 operation in all weather conditions;
video information from the triggering point, which will allow the operator to make a decision in real time;
resistance to external factors (appearance of animals and birds, swaying trees, sources of electromagnetic radiation, lightning discharges, etc.).
Currently, the security systems market has radar systems (RLS) for perimeter and territory protection of civilian facilities that meet these requirements and improve the quality of security of unfenced facilities. Radar is a method of detecting and locating objects using radio waves. The waves are emitted by a radar station, reflected from the object and returned to the station, which analyzes them in order to accurately determine the location of the object. Radars of this class include one or more coherent long-range Doppler pulse radars of the Ku-band.
The coherent radar method is based on the selection and analysis of the phase difference between the transmitted and reflected signals, which occurs due to the Doppler effect when reflecting a signal from a moving object. The transmitting device can operate both continuously and in pulse mode. The main advantage of this method is that it monitors only moving objects, which eliminates interference from stationary objects located between the receiver and the target. Perimeter and territory protection radars are designed for round-the-clock, all-weather protection of objects by means of radar surveillance of the territory, detection of moving targets, measurement of their coordinates and speed, class recognition and automatic tracking of detected targets.
Security radars detect and recognize targets at distances of up to 1 km for a person and 1.5 km for a vehicle in a viewing sector of up to 360 degrees, determine their coordinates and speed of movement. Radars can operate autonomously, together with rotating video cameras and thermal imagers, and perform their functions together with security systems previously installed at the facility.
Some of the security radars available on the market can provide signals to the operator upon detection of a target within pre-set alarm zones. Such systems have the ability to link the graphic plan of the object to the radar map.
As part of a comprehensive security system for facilities, perimeter and territory protection radars can act as target designators for rotating video and thermal imaging cameras. Radars solve the problem of preliminary detection, speed and class assessment of a target at a range significantly exceeding the capabilities of video cameras. Based on the radar target designation, detailed video surveillance of the detected target is carried out using a rotating video camera or thermal imager.
The use of perimeter and territory protection radars is necessary in places where people are constantly present, so it is important that the level of electromagnetic radiation is extremely low. Some domestic developers offer perimeter protection radars, the radiation from which is no more than from a mobile phone.
The use of perimeter and territory protection radars is advantageous from an economic point of view: the Russian market offers systems that have a low specific cost of protecting a linear kilometer (square kilometer) of the perimeter (territory of the facility).
Perimeter security radars consist of an antenna, an external module, an adapter, a server, and an operator's automated workstation (AWS). A single computer can be used as a server and an AWS. Otherwise, the AWS is connected to the server via a local area network. Some security radars provide for the construction of a branched radar or complex review system consisting of an arbitrary number of radars, video cameras, and thermal imagers.
The client application installed on the operator's workstation receives information about the target environment in the form of a map of the viewing area with a coordinate grid and the location of detected targets, which are displayed as mnemonic symbols. The targets are accompanied by information blocks containing information about the coordinates, class and speed. The client application allows displaying video information from PTZ cameras and thermal imagers. Their operation can be carried out automatically based on target designation by the radar or by the operator's command. In the second case, the radar operator controls the video cameras (thermal imagers), indicating the location on the map from which video information must be received.
Perimeter and territory security radars are installed in areas with direct optical visibility. The elevation of the radar antenna above the surrounding area is usually from 1 to 30 m (placement on the roof of a building, mast, bracket, etc.). External equipment is installed taking into account the exclusion of mechanical obstacles during full rotation of the radar antenna.
The use of perimeter security radars will solve existing problems of protecting unfenced facilities and improve the quality of their security. Installation of a fence is not always possible and requires significant time and money. Security radars are installed in a short time, assembly does not require much labor, and the price of the devices is several times lower than the cost of constructing perimeter fences.
Perimeter and territory security radars will increase the level of security for facilities of various purposes.
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1. Catalogue «OPS. Security and fire alarm systems. Perimeter systems»-2005;
2. Magazine «Trade News/NT-Trade Equipment».