1、 Industry development

With the rapid development of China’s economy, air transport industry has also been rapid development. There were 121 civil airports in China in 2000 and 180 by the end of 2011. It is estimated that the number of transport airports in China will reach 230 by 2015. With the rapid development of air transport industry, the airport safety management has put forward higher requirements.

Due to its large area, complex personnel composition and scattered monitoring targets, the airport perimeter area has always been a major difficulty in the field of airport security. Domestic Baiyun Airport in Guangzhou, Changshui airport in Kunming and Bao’an airport in Shenzhen have tried different ways in the field of airport perimeter security.

The perimeter of Guangzhou Baiyun Airport airfield is 30.5km long, which is composed of steel fence and four aircraft taxiing bridges crossing the highway. The main body of the perimeter intrusion detection and alarm system is vibration cable intelligent detection technology, supplemented by microwave opposite detection technology of the position of the taxiing bridge. The perimeter of Shenzhen Bao’an airport is about 14.5km long in total and 4.2km long in total. The main body of the intrusion detection and alarm system of the permanent perimeter adopts the vibration cable intelligent detection technology, while the temporary perimeter adopts the vibration cable detection technology. Based on the private network of terminal security system, Yunnan Kunming airport has gradually built up a mode that takes terminal security system as the trunk, perimeter flight area alarm system as the branch, and gradually expands to access the security subsystem of single functional building outside the terminal.

It can be seen from this that due to the large area around the airport, the surrounding situation is more complex, and the invasion threats are diverse. No matter how powerful a single system is, it will always be limited because of its professionalism. Through the organic integration of multiple functional subsystems, the overall effectiveness of the system will be enhanced by geometric progression on the basis of the original single isolated system. It uses multi-level and multi technology to detect the possible invasion threat, so as to strive for the deployment time of defense forces for the airport as much as possible and provide real-time dynamic information for its actions.

2、 Application scenarios

2.1 threats

Through communication and discussion with a domestic airport, after mastering the intrusion events of the airport in recent years, we summarize and judge the probability of possible perimeter intrusion and the severity of possible consequences, and deduce the corresponding risk level from the formula “probability of occurrence x severity of possible consequences = risk level”:

Design of airport perimeter intrusion alarm system based on Radar Technology

Table 1: intrusion threat analysis table

Note: 1. The consequences from 1 to 5 are almost no impact, little impact, average impact, great impact and catastrophic impact; 2. The probability of occurrence from 1 to 5 is almost impossible, very unlikely, possible, very likely and frequent.

2.2 solution proposal

Through our assessment of the risk level of perimeter intrusion described in Table 1, we found that the four behaviors “terrorist attack”, “airside (runway) unauthorized vehicle entry”, “intrusion attempt against perimeter (early behavior)” and “track tracking for intruder field” are high risk levels, It may have a great impact on the safety and operation of the airport, so the security solutions of the airport perimeter also need to be studied based on these events.

Through the analysis of these behaviors, we find several common points

1. The behavior happens suddenly. Air side intruders, no matter what kind of harmful behavior they want to do, because of the subjective threat of their intention, their behavior is premeditated. Once implemented, the process will not last long, which brings great challenges to security.

2. Diverse roles. The subject of intrusion is uncertain. It is possible that the subject of intrusion is human, vehicle or even UAV. It is difficult to predict the point of intrusion, so it is difficult to find a way to detect.

3. The track should not be tracked. According to the current security technology, it is basically based on single point monitoring or linear monitoring. Once the intruder leaves the defense area and enters into a wider air side area, the area can not be fortified by the existing technology, then the security personnel may lose the target.

Moreover, if the existing security technology is adopted, there are also some problems as follows:

1. At present, the perimeter security system mainly uses the camera as the means of video review, which is bound to bring a lot of trenching and buried pipe wiring (open line is not allowed in the airport aerial survey area), so it is difficult to put the project into practice when the airport requires no suspension of flights;

2. If we only rely on linear alarm system (such as vibration optical fiber technology or vibration sensor technology), according to the actual use of domestic airports, there will be a lot of false alarms, which greatly reduces the efficiency of the technical defense system;

3. At present, the security technology is greatly affected by the weather. If affected by strong wind or heavy rainfall, the false alarm rate of vibration detection technology will rise, and if it is fog or night environment, all conventional video technology will be greatly affected.

Based on the above two types of problems, the technologies needed for airport perimeter security should have the following characteristics:

Automatic detection and tracking of targets: the perimeter system of the airport needs a wide area monitoring system suitable for the perimeter of the airport. If the intruder intrudes into the protection area, the perimeter system will generate alarm information. The system should track the intruder target and use appropriate video monitoring equipment to transmit it to the superior manager through the network, The historical image records can be used for future analysis and evidence collection.

Real time scene awareness and threat perception: the perimeter system needs to be equipped with a geographic information system (GIS) driver engine with comprehensive geomorphic features, which can display the bird’s-eye view of the protection area, display the whole scene of the whole site on a single operation interface, and display the distribution of all sensors and target positioning. The operation interface can be set in the central control room, or set on any computer in the network for management and operation. In order to judge the suspicious scene in the future, the system allows users to click any point on the map, automatically find the latest camera location, and display the real-time video of the area.

Multiple sensor combination and response modes: in order to detect the intrusion targets and potential threats in different types of complex environment of the airport, the perimeter alarm system should combine the advantages of various technologies to detect different forms of open area and complex area, and adopt appropriate technical means to filter out friendly vehicles and personnel, so as to reduce the false alarm rate. The perimeter alarm system can also be easily integrated with other third-party systems.

Low cost construction and operation: the composite perimeter defense system is used to achieve a wide range of perimeter defense and provide 360 ° Compared with other single technology perimeter protection technology, the installation of field front-end detection equipment should be greatly reduced, so as to reduce the amount of system operation and maintenance, and then reduce the maintenance cost of the whole life cycle of the system.

Therefore, an integrated perimeter intrusion alarm system based on radar technology is adopted. As a new perimeter technology, radar perimeter technology completely breaks through the traditional thinking mode of perimeter. Airport perimeter “point line area” management truly realizes 24-hour all-weather airport perimeter prevention, and its core essence is to extend the “transient” management of intrusion behavior to “continuous” management, and realize the management of intrusion events before, during and after. It also includes all-weather safety management, whether in bad wind or fog environment, or dark environment at night, the security system should closely monitor the security situation of the controlled area. Continuous deployment also means complete static deployment, that is to say, the selected detection device will not be distracted by the occurrence of an event, and the device still has complete monitoring capability for the area. In order to cooperate with the use of radar technology, it also uses a set of advanced security information integrated alarm platform as the support, integrates a variety of technologies in a unified information interaction framework, and ensures the security of the airport perimeter to the greatest extent through multi-level detection and review.

3、 Technical characteristics of radar

3.1 basic characteristics

3.1.1 basic principle of detection

Frequency modulated continuous wave (FMCW) radar detection technology can detect the target by measuring the intensity difference of the reflected signal between the target and the background environment (the difference of the radar reflected signal between the interested target and the surrounding environment or static target). In order to reliably detect the personnel standing 1.8m high and minimize the false alarm rate, it is recommended that the signal strength difference be 19dB.

Figure: radar transmitting and receiving electromagnetic beam at set azimuth

As shown in the figure, the target object on the electromagnetic beam transmission path will reflect the electromagnetic energy back to the radar, indicating that there is “something” in this direction. Unless the target object is very large, some electromagnetic waves will bypass the target object and continue to measure the target object further away. Then, our hardware will sample the reflected energy, and calculate the reflected energy every 30cm2 in each azimuth, so as to obtain the ultra-high resolution digital image of the surrounding environment.

3.1.2 detection range

Different types of radar can be selected in different geographical environment, and the radar can also be divided into ground perimeter warning radar, low altitude warning radar and sea warning radar.

The following table only lists the detection range of common radars:

Table 2: detection range of various target radars

3.1.3 tracking

The software can display the position of the “tracking object” (the interested detection target object). Tracking is created by comparing the continuous reflected signal strength of the surrounding environment with that of a moving or stationary person / vehicle. Tracking refers to the continuous detection of the target whose moving mode conforms to the preset predictability.

Taking a radar system as an example, its basic tracking performance is as follows:

Table 3: object tracking performance of radar system

3.2 system advantages

The radar system has the following advantages.

3.2.1 large area multi-target detection capability

If a large range of radar sensors are used, the pre invasion warning and post invasion continuous tracking can be realized in the radar coverage area. The technology should be able to capture moving objects, including acoustic photoelectric warning, video review / tracking, and detect multiple targets at the same time.

Radar perimeter adopts wide area coverage detection, and its coverage is not only the perimeter, but also the continuous area inside and outside the perimeter. Therefore, the radar coverage should be able to detect multiple intrusion targets at the same time.

3.2.2 regional continuous tracking capability

In addition to the basic review, the cameras within the radar coverage can also continuously track the intruder’s trajectory, or switch tracking between multiple targets (limited by the number of cameras). Users can choose the main target to track, but when the camera tracks the main target, other targets will not be lost on the map due to the number of cameras.

3.2.3 multi terrain adaptability

There is a large area of open area around the airport, which is suitable for radar layout. It can realize the detection of single radar with a maximum radius of 1km, and can form the tracking function after invasion that can not be completed by linear perimeter technology, and has strong anti natural interference ability. Radar technology can roughly cover most of the area in the perimeter.

3.2.4 high detection accuracy

Because radar technology does not rely on video images, it will not be unable to detect because of bad weather conditions; It also does not use vibration sensing technology, so it will not be affected by strong winds, heavy rain and so on. Radar technology can obtain the shape characteristic values of human body and vehicle through sampling, so as to distinguish them from animals or other interfering objects near the perimeter, which greatly increases the accuracy of detection.

3.3 limitations

Radar system also has some limitations, some specific scenarios will affect its detection performance.

3.3.1 poor line of sight affects detection performance

In order to track the movement of people or vehicles, radar requires that the target object must be able to continuously reflect electromagnetic beam. In order to ensure stable performance, radar is required to be able to observe the whole body of a person or vehicle, so that it can receive the reflected signals from the upper and lower parts of the person or vehicle. If the upper or lower part of the target object is covered by long grass, uneven terrain, artificial horizontal surface (i.e. raised ground), guardrail and fence, the possibility of detecting the target object will be greatly reduced, and the maximum detection range will also be reduced.

3.3.2 ground background noise affects detection performance

The best condition of ground-based radar detection is on flat and clean ground. Low noise refers to the electromagnetic wave continuously reflected by vegetation to radar. These low-energy reflected electromagnetic waves increase the background noise of radar detection, thus reducing the signal strength difference between personnel / vehicle and the surrounding environment.

4、 Review and use of other technologies

It is precisely because the radar monitoring system will also have certain limitations, so it needs to be used with other technologies. The following two points need to be done in combination.

4.1 integrated platform

Advanced system integration technology should be adopted to base the perimeter alarm system of the airport on an open integration platform. The platform needs to adopt a unified data architecture, which can integrate many third-party technologies and converge to a unified interface, Give decision support to the security operators in the central control room to the maximum extent.

4.2 design based on defense area

Although there is a radar system for a large range of detection system, we still need to carefully design the perimeter according to the concept of traditional defense area. In a single defense area, from one intrusion point to multiple intrusion points, it should be able to cause alarm, and linkage camera for review. If multiple defense areas invade at the same time, the alarms between defense areas should not interfere with each other, that is, each defense area should form an alarm at the same time in case of invasion, and the cameras in each defense area should form a review action independently, so as to prevent the invasion of multi-point breakthrough. Perimeter intrusion alarm system in a single defense area is at least a review system composed of sensors and cameras, in which the vibration fiber needs to be distributed according to the defense area, and video review is also the basic requirement. 4.3 preliminary display of effect

Because the airport perimeter area is usually large and the environment is complex, it is difficult to express with simple text information, so it has great pressure on security personnel. Therefore, the electronic map of perimeter alarm plays a very important role in the work. The electronic map is the basic configuration of intrusion alarm system. Electronic map is a basic information that can be zoomed and panned to show the geographical environment of the airport. All intrusion alarm information will be displayed on it in the form of map points, and distinguished by eye-catching colors, so as to provide security management personnel with clear identification of alarms. Electronic map is also the basic interface of camera operation and control

1. The check image of the intruder should be displayed on the map automatically;

2. For the intruder tracked by radar, the camera should track the target automatically according to its moving position, and can clearly mark the field of view coverage area of the current camera’s shooting position on the map;

3. When the operator needs to use the camera to observe the image of a certain position, the operator does not need to pay attention to the installation position of a specific camera, but only needs to click the position to be observed on the map. The system can automatically select the most suitable camera through the automatic calculation function of the electronic map, and automatically aim at the target position to provide the operator with observation, At the same time, the view field angle of the current camera will be marked on the map.

Editor in charge: GT

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