The role of radar detection alarm system in prison security

    Requirements Analysis of Prison Perimeter Anti-escape System

    There is no perfect, one-step perimeter alarm technology in the world. Various perimeter alarm technologies have their own application environments and system defects. Only by having a detailed understanding of application requirements and targeted design can we design a perimeter alarm system with the lowest false alarm rate and the highest recognition rate.

    The prison industry has its own special environment and application characteristics. To sum up, we can summarize it into the following points:

    The purpose of prison is to prevent prisoners from escaping, and the purpose of detection is to "get close to the wall"; the purpose of prison is to ensure the lowest possible false alarm rate while maintaining the highest possible recognition rate, which has different priorities and focuses compared to ordinary perimeters; prisons mainly solve false alarms from cats (on the ground) and birds (in the air), and the frequency of false alarm sources is different from that of ordinary perimeters; there is often no strict boundary division inside ordinary perimeters, and the boundary isolation zone between the prison wall and the steel mesh wall is prohibited for anyone to enter, while the patrol area is outside the steel mesh wall, where police officers patrol in electric patrol cars, and there are often roads outside the prison wall with social vehicles passing by. The former can define the defense zone width by the detection range of the equipment, and the latter defines the detection range of the equipment by the physical area; prison detection equipment needs to consider the interference of the working conditions of the high-voltage power grid (electromagnetic pulses caused by high-voltage discharge), and the steel mesh wall on the prison wall is a good lightning conductor. Prisons are often located in the suburbs, and separate lightning protection needs to be considered.

    The above restrictions mean that we cannot rely on one perimeter technology to be at ease. We must choose two or more technologies and organically integrate the data of these technologies to design an effective prison perimeter anti-escape system. Specifically, we need to consider the following four aspects.

    Behavior of entering the 5-meter warning tape:

    Hidden dangers: Traditional perimeter alarm technology generally uses cross-fire or leakage field technology, which either has too high false alarm rate or is easily deceived or stepped over by suspects, and has no target positioning capability at all, and can only output dry node signals. In order to save costs, many XX prison users often configure a defense zone every 100 meters, which makes a single defense zone too long. Once an alarm is triggered, the camera basically cannot see the situation of the 100-meter defense zone clearly, which is easy to cause misjudgment.

    Design requirements: 640x960 time period around the clock (police officers can re-customize time periods). When a suspect enters the 5-meter warning area of ​​the wall: automatically detect any intrusion; automatically locate the intruder's intrusion position (accuracy 50 cm); automatically display the intruder's position on the electronic map; automatically pop up the camera screen linked to the radar; automatically record police information; automatically link to the on-site alarm; automatically control the high-speed ball to point to the intruder, and automatically zoom in and out to track the intruder; real-time video recording and video retrieval and playback.

    Prison wall climbing behavior

    Hidden dangers: Traditional perimeter alarms generally detect climbing over a wall from outside to inside, so climbing over the wall is the first checkpoint. The action of climbing over the wall generally only lasts 1-5 seconds. Once a climbing action is detected, while the on-duty personnel have time to review the image, the security guards can manually and effectively identify the intrusion location and where the target may be hidden.

    However, the requirements for prison perimeter security are exactly the opposite. Climbing over the wall is the last move of the prisoner. Once the prisoner climbs over the wall and enters the social area within a few seconds, the armed police will not have time to arrest him, thus missing the opportunity. Therefore, the final detection point is actually the wall. Once someone is found trying to climb up, their behavior can be quickly detected and the target's movement can be continuously tracked, thus buying precious time for the armed police on duty.

    Design requirements: 640x960 time period around the clock (police officers can re-customize time periods). When the suspect approaches the wall and climbs up the wall, the rest of the design requirements are the same as above.

    High rope escape

    Hidden danger: According to the requirements of the Ministry of Justice, most prisons have added a steel mesh wall to the existing prison wall, but this brings a new hidden danger: when suspects set up high-altitude ropes or bamboo poles from nearby buildings or high points, they can avoid the high-voltage power grid and slide directly to the top of the heightened steel mesh wall, making it easier to escape. Design requirements are the same as above.

    Armed police post blind spot detection

    Hidden danger: The corner of the armed police post is a 90-degree arc, and it is difficult for ordinary perimeter alarm equipment to achieve seamless protection. It is difficult for the armed police on the post to observe the situation under their feet, and it is difficult for the armed police on the opposite side to see the situation at the corner of the other side 200 meters away. At night or in light fog, it is easy to become a loophole in the deployment. The design requirements are the same as above.

    Prison radar three-dimensional perimeter anti-escape design

    The three-dimensional perimeter anti-escape design of the prison, as the name suggests, is to build a three-dimensional defense system, combining points, lines, and surfaces. It can not only protect the ground area, but also the vertical area of ​​the wall, and can protect the escape from the air. What's more, it can weave a dragnet to prevent prisoners from escaping from the air or the underground caves, truly becoming the guardian of the prison officers.

    At the same time, this system is not affected by the external environment (wind, rain, thunder, lightning, fog, sandstorm) and electromagnetic interference. The system is both advanced and scientific, reliable and practical. It should be optimized and designed based on the principle of high quality, high technology, high standards and high cost performance, and under the premise of focusing on key areas, so that the whole system can play the greatest role.

    Front-end detector selection

    Perimeter alarm technology has been around for more than 40 years, and different alarm sensors have different detection characteristics. Generally speaking, they are mainly divided into perimeter sensors and space detection sensors.

    Generally speaking, any high-security project requires at least two or more sensors to realize sensor data and/or combination, so as to obtain high recognition rate and low false alarm rate. IoT anti-intrusion technology has made a qualitative leap in traditional perimeter alarm technology, realizing sensor alarm detection, target positioning, target tracking, multi-sensor data fusion and other technologies for the first time. For high-security projects such as prisons, it has made a great step towards the goal of zero false alarms and zero missed alarms.

    Based on the author's many years of anti-intrusion technology research and field testing experience, different projects have different levels of anti-intrusion detection requirements, but when selecting technology, we generally evaluate the following four main parameters to truly determine which product is most suitable for our project.

    Probability of Detection: Generally speaking, it is required to identify suspicious intrusion targets (people), staying in prohibited areas, breaking into prohibited areas, and climbing over prohibited areas.

    False Alarm Rate: For all sensor technologies, a high false alarm rate is the most unbearable, especially for weather such as sunshine, temperature changes, wind, rain, snow, dust, fog, and other daily interference that cannot be avoided. Other interference sources include electromagnetic waves, artificial light sources (car lights, street lights, city beautification lights), various shadows, etc.

    · False alarm rate/false alarm rate (NuisanceAlarmRate): In principle, alarms generated by organisms such as reptiles and birds need to be identified as much as possible.

    ·Target positioning accuracy: Since the intrusion target moves very fast, the target may move quickly to the obstruction within a few seconds, and the on-duty personnel cannot observe the target, which may be judged as a false alarm. Therefore, meter-level positioning accuracy is necessary in some environments. The following are the main technical features of the three common prison perimeter alarm technologies on the market:

    After the above comparison and selection, the author recommends using microwave radar and lidar as front-end detection equipment, which are also the most suitable basic modules for the "radar three-dimensional perimeter escape system" we want to build.

Microwave radar, as a large-area space detection and positioning technology, will be used in the 5-meter warning isolation zone to detect any intruding targets and locate their coordinates.

    As a large-area 2D plane detection and positioning technology, LiDAR will build a virtual laser wall 20 cm parallel to the wall. Any target trying to climb the wall will be detected by the LiDAR and the intrusion location will be prompted. The target coordinates output by the two radar technologies are transmitted to the PTZ camera, which can continuously track the intruder.

    5-meter warning belt: microwave radar

    As a military-grade product, the 24G microwave radar not only supports large-area surveillance with a target recognition rate of 100%, but can also locate the target with a positioning resolution of 25 cm. In this way, in conjunction with a PTZ camera, it can continuously track intruding targets.