Research On Real-Time Imaging Method Of Ultra-low Altitude Airborne Transient Electromagnetic

Airborne Transient Electromagnetic(ATEM)has made considerable development since it was around in 1950 s.Nowadays ATEM is widely used in mineral exploration,groundwater exploration,geological disaster investigation and so on.As an important transient electromagnetic method,and it has got more and more geophysicists' attention because of its high efficiency?width of detection of area?low exploration cost and ability to cope with complex exploration environments.However,there are still many problems need to be solved and improved for ATEM in shallow underground work,which is the foothold of the study in ultra-low-altitude transient electromagnetic method in this paper.On the one hand,previous ATEM lost the detection accuracy while having the advantages of large range of detection,exploration depth and high work efficiency,and so was the resolution of the shallow underground anomalous geological body.On the other hand,conventional surficial transient electromagnetic method also has decent resolution for superficial anomalies.However,it has a low work efficiency and high exploration cost in the way of manual work,and there are some detection area which is in complex geological environment and can't be entered for it,which makes the work not be accomplished.Aiming at the two points above,the study of the transient electromagnetic method of ultra-low altitude air makes a great significance in expanding the Application field of transient electromagnetic method and solving practical production tasks.Based on previous studies,this paper proposes a method for the full field apparent resistivity definition,which is suitable for airborne transient electromagnetic,and solves the problems of the traditional definition method of apparent resistivity.Aiming at the superiority of ultra-low-altitude transient electromagnetic method in detecting shallow underground work,three-dimensional FDTD forward modeling is carried out for the underground small overlapped anomaly bodies,mines and underground unexploded bombs in this paper.I have studied the theoretical feasibility of the transient electromagnetic method of ultra-low altitude air by comparing the distribution characteristics of electromagnetic field,attenuation curve and apparent resistivity of abnormal body.At the same time based on the forward data,I programed the software interface of the ultra-low-altitude transient electromagnetic real-time imaging on GUIDE tool in MATLAB programming language.The real-time imaging of forward data can be used as a basis for on-site field data acquisition in ultra-low-altitude transient electromagnetic field in future production practice.In this paper,based on the one-dimensional forward modeling,through the research on the device?detection principle and definition of apparent resistivity of ultra-low-altitude transient electromagnetic method,I carried out three-dimensional FDTD forward modeling on several typical shallow abnormal body models and analyzed the forward modeling results,which theoretically proved the feasibility and reliability of ultra-low-altitude transient electromagnetic.The software interface based on forward modeling data was programmed by using GUIDE tool of MATLAB language to realize the real-time imaging of ultra-low airborne transient electromagnetic detection.