Automatic Identification Of Underground Pipeline Based On Ground Penetrating Radar

Underground pipelines in cities are complex and diverse,and bear important missions such as energy and information transmission.If information on the location and depth of underground pipelines cannot be grasped,it will have a great impact on urban life and construction.The detection of pipelines and the establishment of an underground pipeline information system are very important.For the early buried underground pipelines,most of them lacked information,and the existing pipeline data also had the problem of imperfect and inaccurate information.In thi s case,high-efficiency and high-resolution detection technologies were needed to detect the underground pipelines.Ground Penetrating Radar(GPR)is a real-time,high-efficiency and non-destructive detection technology.It has the advantages of fast detection speed,high resolution,simple operation,and wide detection range.Therefore,it is the preferred method for urban underground pipeline detection.After studying a large amount of data,this article has started to develop a high-speed information acquisition board that can be used in the time-domain ground penetrating radar system.The acquisition board uses FPGA as the main control chip,and uses a digital frequency synthesizer to generate the antenna trigger signal,through analog-to-digital conversion.The device collects and finally completes the acquisition,storage,and processing of radar echo signals.The acquisition board communicates with the upper computer through the Ethernet port,achieving high-speed transmission of information.The information acquisition board adopts the equivalent sampling technology when collecting the radar echo signals,and achieves the process of sampling ultra-wideband pulse signals with a lower sampling rate.In this paper,after the development of the acquisition board,the automatic identification technology of underground pipelines is studied.First,the characteristics of underground pipeline echo signals are analyzed,and the hyperbolic characteristics of pipeline echo signals are quantitatively analyzed.Then,the collected echo images are preprocessed and edge-extracted.Pre-processing includes removing the direct wave in the echo signal and suppressing the random noise.After researching,using the mean method to remove the direct wave,using the wavelet transform threshold method to remove random noise can achieve good results.For the edge extraction of echo image,the Canny operator in the micro-molecule operator is used.In the case of no noise,the extraction of the edge of the target echo is very satisfactory.In the noisy case,the edges extracted by the Canny operator are garbled and discontinuous.In the paper,the image expansion is used to process the extracted edges,and good results have also been achieved.Finally,the geometric relationship between the point on the edge of the extracted hyperbola and the position of the pipe vertex and the diameter of the pipe is analyzed.Three points on the edge of the hyperbola are selected and the position and radius of the circular pipe is determined by the method of “three points determine cicle”,achieved the purpose of automatic identification of the pipeline in this paper.