The Development Of Receiving System And Data Preprocessing On The Grounded Electrical Source Airborne Transient Electromagnetic Method

As the growing requirement of the exploration of the environment,engineering and mineral resources in complex terrain areas in recent years,the traditional detection methods on the ground have the lower efficiency on acquisition and poor measurement accuracy influenced on the terrain,water,swap and other conditions.And it is difficult to explore on special areas.Airborne electromagnetic exploration technology can overcome the above difficulties,but is not suitable for small and medium-sized exploration missions due to the heavy load and high exploration costs.An electromagnetic exploration method is proposed using ground transmitting and the receiver suspended by an unmanned aerial vehicle on air.GREATEM(grounded electrical source airborne transient electromagnetic)emits the primary field from an electrical source or loop source on the ground.The receiving system is suspended on an unmanned aerial vehicle or airship to induce the secondary field signal on the air.By analyzing characteristics of the secondary field response signal and other parameters,geostatistionary inversion is carried out in order to detect the structure,physical properties and spatial distribution of underground geologic bodies.For the purpose of increasing the radiation range and detection depth,the electric dipoles wire is employed with high power.GREATEM gets the advantages of rapid,flexible,economical and efficient exploration in any application.There are more problems with GREATEM system,such as the lower sensitivity,the lower asynchronous precision of sampling,the superposition of desired signals and various noise with lower signal to noise ratio(SNR).In this paper,based on the study of the receiving system of GREATEM and preprocessing method,it is proposed that CEEMD-AF to suppress baseline drift and the deep learning networks LSTM-AE to improve SNR.By the development of the electromagnetic inductive sensors and the receivers instrument,the result indicates that the receiving system and preprocessing method improve the receiving performance and data quality on indoor standardized test,outdoor and landfill application.The research of paper is as following:(1)Based on the analysis of the electrical parameters of the electromagnetic inductive sensor,the lower noise and convenient electromagnetic inductive sensor is designed for GREATEM.It is shown that the theoretical derivation of the distributed capacitance,distributed inductance,bandwidth,matched resistance and resonant frequency in detail.And the coiling and test scheme of coil is presented.The fully differential preamplifier circuit is developed and tested with the features of lower noise,high linearity,lower distortion.(2)The portable receiver is developed with high precision,high sampling rate and multiple communication interfaces.The study of the key technologies is shown,such as crystal calibration,synchronous acquisition,instrument calibration,high speed data buffering and the conditioning circuit applied to various kinds of sensors.And the scheme of the receiver is presented.The receiver is developed with all kinds of sampling rates,lower noise,higher dynamic range,higher synchronous accuracy and instrument self-calibration.Lastly,it is shown that the developed receiver meets the detection requirements of GREATEM system parameters by the standardized test.(3)The paper proposes a denoised method called complementary ensemble empirical mode decomposition adaptive filtering(CEEMD-AF)based on CEEMD and iterative filtering to suppress noise caused by baseline drift.Through the processing of simulated data and field data,the results show that the CEEMD-AF method is better than the wavelet decomposition denoising method to suppress the false geological anomalies caused by baseline drift.(4)The paper proposes a denoised method called long short time memory auto-encoder deep learning network(LSTM-AE)based on LSTM and AE,and optimized the loss function of the model to improve SNR for the secondary field signal.Through the processing of simulated data and field data,the results show that the LSTM-AE method is better than the wavelet threshold denoising method.(5)It is demonstrated that the test and data processing method in detail on the standardized platform and field trial.The comparison and analysis of the receiving system with multi-channel receiver developed by Aerospace Information Research Institute,Chinese Academy of Sciences and V8 multifunction receiver developed by Phoenic Geophysics Limited Canada,it is consistent that the curves of the secondary field signal.Subsequently,the application of the receiving system on landfill is carried out.After processing the data of 1 line on the survey area,the resistivity profile image is shown.The comparison and analysis of the resistivity profile image on ground,it is effective that the validity of data collected by the developed receiving system.In a word,with the requirements of GREATEM detection,it is proposed that the development of electromagnetic inductive sensors,the development of the receiver instrument and the preprocessing method of the CEEMD-AF and LSTM-AE network.It is of great significance for application and popularization of GREATEM to develop the receiving system and improve preprocessing methods.It also provides an effective exploration method,technology and instruments for geological exploration in a special environment.