抄録
Detection of leaks in a busy urban environment is an important problem. Walking surveys do not easily inspect street locations. Extractive and fixed path optical vehicle mounted system do not survey the entire street width. The Japan Gas Association in support of the Japan National R & D Project Against Pipeline Leaks undertook the development of a differential absorption LIDAR (DIAL) system for sensitive detection of methane in natural gas leaks. This paper presents the concept of this laser system, receiver, processing and display and its implementation. The compact laser system, electronics and all support hardware were mounted inside a Toyota RAV-4 vehicle and delivered to JGA in early 2004. The DIAL system was designed to image the street surface directly in front of the vehicle. A 4-m wide by 4-m deep footprint is imaged with 0.5 m by 0.5 m resolution starting approximately 2.5 meters in front of the RAV4. This DIAL system determines methane leak concentration by comparing the measured reflectance from two sets of laser pulses separated slightly in wavelength. The ratio of the absorbed to non-absorbed light determines the concentration. This system was designed to detect leaks 10 ppmV/m and greater. Our system was tested with various calibrated methane-filled pillows representing severaleak equivalences
