| As a supplement to the traditional aeromagnetic survey,UAV aeromagnetic survey has been widely used in geological survey,resource exploration,underwater magnetic target detection and auxiliary navigation due to its advantages of small size,low cost,less human intervention,and no potential safety hazard.Multi rotor UAV aeromagnetic survey is an important part of the survey,which is suitable for large scale aeromagnetic detailed survey in small and medium areas,and can be used as an effective supplement to large-scale aeromagnetic survey and ground magnetic survey.The original magnetic field data of UAV aeromagnetic survey include geomagnetic field data,interference of UAV platform,interference of equipment and fluxgate sensor steering error interference.In the aeromagnetic anomaly map,the interference is mainly manifested as strip anomaly along the survey line direction,which seriously affects the accuracy of geological anomaly interpretation and needs to be compensated.In this paper,the aeromagnetic compensation research is carried out based on a set of aeromagnetic measurement system composed of an electric quadrotor UAV equipped with high-precision fluxgate magnetism,and the main research contents are as follows:According to the source,aeromagnetic interference can be divided into two categories:one is the noise generated by the work of mechanical and electrical equipment and the external environment.Compared with the geomagnetic signal,this part of the interference belongs to high-frequency noise,which can be preprocessed by designing a reasonable filter.The other is airborne platform interference and sensor error,which can be processed by modeling analysis,that is,compensation processing.Aiming at the noise interference problem of the multi rotor UAV aeromagnetic system,this paper carries out the static test experiments under different states of the system,aiming to get the main source,influence size and spectrum characteristics of the noise interference of the aeromagnetic system through the data spectrum analysis results,and design the corresponding low-pass filter according to the high-frequency characteristics of the noise interference for error processing.In this paper,based on the Tolles Lawson model,the compensation models of instrument steering error and flight platform maneuver error are established.According to the similar structure of the two models,the comprehensive compensation model is established,and the least square algorithm is used to obtain the comprehensive compensation parameters,and then the aeromagnetic data of the work area is compensated.Aiming at the particularity of attitude self-adjusting of multi rotor UAV aeromagnetic system,this paper studies the flight scheme of Leliak aeromagnetic tetragonal compensation test,carries out the comparative experiment of aeromagnetic tetragonal compensation test and ground tetragonal compensation test,and analyzes and evaluates the compensation effect of the two compensation test methods.Aiming at the problem that the assumption of constant geomagnetic field of Tolles-Lawson model affects the compensation accuracy,this paper studies the influence of geomagnetic field gradient on the compensation accuracy and the prediction of geomagnetic field by Kalman filter,aiming to improve the compensation model and improve the compensation accuracy by predicting geomagnetic field by Kalman filter.Aeromagnetic total field horizontal gradient data can better reflect the weak changes in the horizontal direction of the magnetic field,which has the advantages of not affected by daily variation,effectively suppressing the background field,highlighting the regional field and the boundary of geological anomaly body,and can effectively make up for the lack of total field data in geological interpretation.In this paper,based on the research results of multi-rotor UAV aeromagnetic total field comprehensive compensation,the research of aeromagnetic total field horizontal gradient compensation is carried out,aiming at constructing gradient compensation model for interference compensation processing.Aeromagnetic three component data can better indicate the geological body information,which is of great significance for aeromagnetic data polarity and remanence research.However,UAV aeromagnetic three component data contains carrier interference error and attitude error,which need to be compensated.In this paper,six kinds of mutual transformation matrix differences between geographical coordinate and carrier coordinate system are analyzed.It is determined that the error of attitude calculation in yaw-pitch-roll sequence is the smallest,and the attitude compensation in roll-pitch-yaw sequence is selected.In this paper,according to the high-frequency characteristics of carrier eddy current interference,a low-pass filter is set up for data preprocessing.Based on the carrier interference compensation model and attitude compensation,an aeromagnetic three component comprehensive compensation error objective function is constructed.An adaptive random step cuckoo search algorithm is innovatively introduced to seek the minimum value of the objective error function through Levy flight,and the three-component aeromagnetic compensation parameters can be obtained quickly and efficiently.In order to verify the compensation effect,the 1:20000 UAV aeromagnetic operation was carried out in a 22km~2 work area in Wuhu,Anhui Province.The field data acquisition work took 3 days to complete,reflecting the efficiency and practicability of the multi rotor UAV aeromagnetic system.After comprehensive compensation processing,correction and leveling processing,the total accuracy of aeromagnetic total field data meets the requirements of high-precision magnetic survey,and the compensation effect is verified.Finally,based on the Euler deconvolution method,the UAV aeromagnetic total field data are inversed,and the Euler inversion results and geological information are comprehensively used to effectively divide the abnormal zone and fault structure,delineate the magma distribution area,and provide reliable geophysical data for the later geological prospecting work in the work area. |
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