Debris-Flow Monitoring System with Acoustic Sensing and Digital Image Processing

本研究的目的是开发一种新的监测系统，以预防和减轻泥石流灾害。本文历时三年的研究成果如下：与其他地面振动传感器、地震仪、压电传感器或动圈传感器相比，将麦克风置于地下管道内的声学传感器具有较高的信噪比。一种改进的声学传感器将麦克风浸入油管内的油中，显示出两倍探测范围的可能性。基于泥石流视频图像的数字图像处理可以利用MPEG运动向量检测算法进行接近检测。另一种数字图像处理方法，如基于计算机的空间滤波测速法、时空导数空间法、互相关法等，可以估计泥石流的表面速度。一种声学传感器与图像处理方法相结合的系统可能具有良好的泥石流监测性能。在大雾或大雨等恶劣天气条件下，声传感器可以弥补图像处理的不足；另一方面，该图像处理方法可以清晰显示声传感器无法观测到的泥石流真实图像。不幸的是，这种组合系统的可行性试验尚未得到证实，因为在试验洪流中没有发生泥石流。2001年11月5日至6日在瑞士伊提根-伯尔尼的瑞士国家水文和地质调查局举行了一次关于泥石流监测的讲习班，部分支持了这一发现。本次研究成果在研讨会上进行了介绍，并对今后泥石流监测工作进行了很好的评价。

The purpose of this research is to develop a new monitoring system to prevent and to mitigate debris-flow hazards. The results of this research during three years are as follows:1. An acoustic sensor with a microphone inside a pipe set underground has a high signal-to-noise ratio compared with other ground vibration sensors, seismometer, piezoelectric sensor, or moving-coil sensor. An improved acoustic sensor having a microphone immersed in oil inside the pipe shows a possibility of twice detection range.2. A digital image processing based on video images of debris flow can make a proximity-detection by utilizing a detection algorithm of MPEG motion vectors. Another digital image processing methods such as computer-based spatial filtering velocimetry, spatio-temporal derivative space method, or cross-correlation method can estimate surface velocity of debris flow.3. A combination system of an acoustic sensor and an image-processing method may have a good performance of debris-flow monitoring. The acoustic sensor may compensate the image processing under a bad weather condition of deep fog or heavy rain : on the other hand, the image-processing method makes clear the real image of debris flow, which the acoustic sensor can't observe. Unfortunately, the feasibility test of this combination system has not been confirmed because debris flows have not occurred in a test torrent.4. A workshop on debris flow monitoring was held at the Swiss National Hydrological and Geological Survey in Ittigen-Bern, Switzerland, on 5-6 November 2001 by partial supporting of this found. The results of this research were presented in the workshop and took a good evaluation in viewing future monitoring of debris flow.