A New Imaging Method Of Ground Penetrating Radar

Ground Penetrating Radar(GPR)is a shallow geophysical exploration technology to investigate underground anomalies according to the differences in dielectric properties and electrical conductivity of different underground media in the target area.Because of its nondestructive,high resolution,convenient and other advantages,it is widely used in geological exploration,civil engineering inspection and lunar exploration and other fields.The measured radar profile acquired in the field shows a distorted and distorted image,which is not consistent with the real underground structure.The migration technique is to move each inconsistent reflection point in the GPR record to its real location,thus obtaining the true image of the subsurface anomaly.However,several commonly used migration algorithms,such as diffraction superposition method and Kirchhoff migration method,have problems such as the inclination limit of data processing and the accuracy of migration equation,which lead to poor migration effect and low computational efficiency.Based on the above reasons,this paper explores a new method: Reverse time migration imaging method based on ray theory.In this paper,the Italian ris-k2 GPR instrument is used to collect field data,and then its data decoding analysis and reverse time migration algorithm are studied.First of all,in the early data acquisition process of GPR,the parameter selection of RIS-K2 GPR has a great influence on the detection results.For example,the size of the antenna frequency,which affects the depth and resolution of detection;The size of the window is determined by the depth of the target body and the dielectric constant of the target region.Secondly,data acquisition using the RIS-K2 GPR in the field is only a part of the preliminary work of the study.Through the research on the RIS-K2 GPR,it is found that the GPR equipment produced by the company encrypt the collected data.Therefore,the measured data must be decoded and analyzed before the GPR data interpretation and processing to determine the format and meaning of the measured data file used by RIS-K2 GPR.The file is composed of three parts: file header,track header and data body.This paper uses C# language to write data decoding and reading programs to decode and analyze relevant data files.Finally,according to the idea of reverse time migration imaging in seismic exploration,the propagation velocity of electromagnetic wave in conductive medium is analyzed,a new algorithm of reverse time migration imaging is designed,and the program code is written,and the algorithm is verified with the measured data.The preliminary test results show that the algorithm has some effect,but it is not obvious and needs further study.The main research contents of this paper include the following parts:(1)Data decoding of RIS-K2 GPR: by referring to literature and previous analysis of recorded data files,the format of original recorded data files of RIS-K2 GPR is mastered.A program is written in Microsoft Visual Studio using C# language to decode the RIS-K2 GPR data and obtain the original recorded data.(2)Research on reverse-time migration imaging algorithm: Based on the principle of seismic reverse-time migration imaging,a new reverse-time migration algorithm was designed based on the characteristic that electromagnetic wave propagates at a speed lower than the speed of light in underground strata,and a program was written to realize it.(3)Analysis of GPR reverse time migration imaging effect:Found by comparison and ground penetrating radar(GPR)reverse-time migration imaging algorithm,compared with other migration methods,writing of GPR reverse-time migration imaging applications using ray theory of superposition of wave field imaging method,avoiding the approximation of wave equation,and this method is not restricted by Angle,has the good imaging effect,the imaging of high precision,fast calculation efficiency,convenient operation,and many other advantages.