Study On Reduction To The Pole Methods In Low Latitude Area Of Large Region

Magnetizing pole is a basic work of magnetic anomaly processing and interpretation,which is to convert oblique magnetization anomalies into vertical magnetization anomalies,so that the processing and interpretation of magnetic anomalies are relatively simple.In the middle and high latitudes,the normalization method can obtain relatively ideal polarization results.However,in the low latitudes,because the polarization factor is an amplification function,the normalization method will produce a large error,especially when the magnetic inclination tends to zero,the polarization results are completely banded.At the same time,in a small range of magnetic survey data,the central magnetic dip Angle of the study area is often selected for pole transformation.However,for large area magnetic anomaly processing,the single geomagnetic dip Angle will produce non-negligible errors,which will be more serious in low latitudes.Therefore,in order to improve the resolution of magnetic survey and the accuracy of interpretation,this paper studies the polarity method of variable magnetic dip in large area and low latitude area.The main study contents and achievements of this paper are as follows:(1)In consideration of the actual situation,in-depth study of different latitudes,using a single dip Angle and variable dip Angle forward magnetic anomaly error size,analysis of the low latitude region,especially near the equator to consider the necessity of variable dip Angle;(2)In the frequency domain low latitudes regionalization is stability,on the basis of studied by a factor of several low latitudes principle-a method to suppress factor method,hyperbolic cosine method and improved pseudo Angle method,design and low latitudes,model experiment result extremely comparing various methods of analysis of their advantages and disadvantages;(3)The dipole equivalent source variable dip method is studied in depth,the algorithm principle of solving linear equations is compared and analyzed in detail,and the theoretical model is used for verification.The problem of equivalent source placement is studied,and the influence of equivalent source depth setting on magnetic anomaly fitting and polarization precision is deeply analyzed,and the reasonable depth setting range is given.For magnetic data of undulating observation surface,the equivalent source model and observation points are arranged as changes with topography,and the vertical magnetization anomalies under undulating topography are obtained by inversion.(4)To study the big point variable angle in a region is extremely method,and combined with frequency domain methods for preparation very low latitudes,validated model applied to low latitudes change Angle,considering the actual situation,analyzed the point by point change Angle change equivalent source method and Angle is changed very method in different latitude localization error,this paper demonstrates that the proposed equivalent source variable Angle extremely the superiority of the method.Finally,the equivalent source variable dip polarizing method is applied to the measured data in the Indian Ocean,and the high precision polarizing results are obtained.