Brief Analysis on Application of Radar and Video Linkage System

    In the wide-area video surveillance fields such as forest fire prevention, border defense, coastal defense, ports, and oil fields, the application of long-distance and ultra-long-distance video surveillance products is becoming more and more extensive. They not only integrate visible light and thermal imaging observation cameras, but also have fog-penetrating functions. They can also detect targets with the help of auxiliary light sources or thermal imaging at night. The image information has both spatial and temporal resolution capabilities; it contains both information about the detected object and information about the spatial environment of the scene; it contains both static and dynamic information about the observed target.

    The system is relatively intuitive and helpful for judgment, but some problems were also found in the actual use process, such as: affected by optical visibility, the observation range is limited in bad weather; it is unable to detect the accurate position, geographic information, speed and other information of moving targets. Taking ordinary civilian fishing boat radar as an example, it can identify more than 500 targets within 6 nautical miles around, calibrate the target's location information (latitude and longitude), navigation information (course speed), radar information (echo area) and other data. Compared with the optical detection method, radar can search over a large range, is not affected by optical visibility, and obtains high accuracy of moving target information, but the target information obtained is relatively abstract. If these two systems can be integrated, it will be helpful to the development of wide-area video surveillance. This article will focus on the application of radar positioning video linkage system.

    1. System Introduction

    The video linkage system based on radar positioning uses computer system software to link the target space/geographic location data obtained by the radar with the rotation angle and lens focal length of the long-distance photoelectric turntable/wide-area monitoring camera to achieve real-time review of the scene image of the space and geographical location. The system consists of positioning radar, long-distance photoelectric turntable/wide-area monitoring camera, server, system software installed on the server, transmission system, etc.

    The radar adopts mature products and has an SDK package for secondary development. The secondary development and integration of software can realize the video linkage monitoring of radar detection targets. Compared with the conventional long-distance monitoring system, the radar and video linkage system has the following advantages: first, the target detection speed is fast; second, multiple targets can be detected at the same time; third, it is less affected by meteorological conditions and has high detection accuracy; fourth, the system is fully digitalized, networked, intelligent, and highly informationized.

    The main functions of the system are: detecting and monitoring targets (people, vehicles, ships) within a range of 20 km; continuous detection day and night; tracking the movement of designated targets; and marking targets on the map.

    2. System Principle

    Based on the existing mature long-distance video surveillance and radar target automatic tracking technologies, the system realizes the digitization, intelligence and networking of radar far-side detection and optical equipment through automatic synchronization of video surveillance system and radar target information, injecting new blood into the application field of wide-area video surveillance.

    The system consists of front-end detection equipment, signal acquisition and processing system, network transmission and analysis control system, etc. It is a multifunctional information comprehensive system with radar video information and video image linkage recognition, moving target tracking and monitoring, coordinate azimuth map positioning, network transmission, information fusion, active early warning and other functions. It solves the problems of slow video search speed, poor accuracy, and cumbersome manual control, improves the use efficiency of long-distance video surveillance systems, improves the speed and accuracy of target search and tracking, reduces the workload of on-duty personnel, and improves the use value of the system.

    The operating principle of this system is that the radar can search and obtain information on surrounding targets within the detection area, and the radar information processing system processes the time series radar images, and automatically identifies, tracks and calculates motion parameters of target echoes in the images; limited by the radar's working system and working principle, the data update speed is greater than 2.4s, and the azimuth data accuracy is lower than the distance data accuracy. The azimuth accuracy of general civilian radars is within 1 degree, and the distance data accuracy is within 1% of the range.

    First, the system uses the open SDK package of the radar product to extract digitized map data, target information and other key data, and sends it to the terminal control server through the network. The server completes the calibration of the virtual scene pixel coordinates and the real coordinates of the software map (the scene installed at the general monitoring point is relatively fixed, and the GIS map of the detection area can also be directly imported).

    Secondly, the target image is collected and encoded and transmitted through the front-end video detection and acquisition equipment that integrates high-definition cameras, ultra-long-distance electric zoom fog-penetrating lenses, and high-precision heavy-duty wind-resistant photoelectric turntables. The target that has just entered the detection range is identified through the image analysis algorithm of the back-end software platform, and the type of target is given: people, cars, and ships, so that the virtual icon corresponding to the target type is marked on the software map. At this time, the virtual icon displayed in the software map can show the real geographical information location. For targets indoors in the detection area, as long as they are covered by the video surveillance system, they can also be marked on the software map through video analysis.

    Third, for the tracking target locked by the radar, the system automatically inputs the position coordinates of the corresponding target into the long-distance optoelectronic turntable, and the coordinates directly correspond to the preset points of the long-distance optoelectronic turntable. The target's motion tracking adopts the video analysis method, and the platform software drives the long-distance optoelectronic turntable to continuously track and shoot, and displays the target's motion trajectory on the software map. At the same time, the real-time image of the moving target will also be displayed accordingly in the software interface.

    Since the long-distance optoelectronic turntable used by the system integrates thermal imaging and auxiliary light sources, the corresponding target images can be acquired even at night.

    3. Brief Analysis of System Application Technology

    The system combines the detection advantages of radar with the characteristics of video images, and brings a new video surveillance experience through software processing. Several key application technologies are listed below.

    1. Target Detection

    The purpose of target detection is to identify the type of target in the defense area, so as to adopt different defense measures. The targets detected by radar are not intuitive, so video analysis is used to segment the moving targets in the video scene, and then the targets are distinguished after being compared with the target model, so that they can be displayed on the map more intuitively.

    2. Target Tracking

    The purpose of target detection is to record and track the movement trajectory of the monitored target, review the target type, continuously monitor the target and identify the details. Since the video may involve multiple moving targets, the video analysis algorithm has high requirements and requires continuous and uninterrupted tracking of the target locked by the radar.

    3. Hardware Technology

    Video images are heavily dependent on optical conditions. According to the meteorological and geographical conditions of the defense area, the corresponding equipment should be matched according to local conditions. Since the system uses high-definition cameras, the process requirements of telephoto lenses are relatively high. Secondly, in the long-distance monitoring process of up to 10km, the stability and accuracy of the PTZ operation are very high. The 0.5° accuracy in the industry standard corresponds to a distance deviation of nearly 88 meters, so the process requirements for hardware are relatively high; the equipment used is used in areas such as the seaside and mountains, low pressure, high altitude, high heat and humidity, saline-alkali corrosion and other environments, requiring the hardware to have good environmental adaptability.

    IV. Conclusion

    China has a long coastline and border, numerous ports, and many mountains and hills. Most of the systems currently built have not yet been integrated. As society and the country pay more attention to public safety, the radar and video linkage system has good market application demand and prospects. At the same time, the system is also an important tool to improve the value of wide-area video surveillance systems, the work efficiency of on-duty personnel, and the level of risk prevention. The use of this system can also fully achieve the purpose of prevention to ensure safety.