Abnormal STEC Detection And The Computerized Ionospheric Tomography

The Computerized Ionospheric Tomography(CIT)based on The Global Navigation Satellite System(GNSS)is the major means of getting the three-dimensional space structure of the ionosphere.Since CIT is a process of correcting the initial electron density in the inversion region according to the difference between the observed value of the STEC obtained from the ground station-satellite signal rays and the value of the algorithm model,the error of STEC observations will directly affect the accuracy of CIT.Therefore,in this paper,a method for detecting abnormal ray STEC observations is proposed and correlated the CIT experiments are carried out.The innovative points in this essay are as follows:(1)A method of detect STEC of abnormal rays which based on MART is proposed.In the calculation process of MART algorithm,the STEC data of each ray is calculated to judge the correction situation generated by the grid through which it passes.According to the frequency of abnormal correction produced by the STEC data,it is determined whether it is abnormal STEC,so as to achieve the purpose of detecting abnormal STEC data.The simulative experimental results show that this method can detect abnormal rays more accurately and effectively.When the correction threshold is 3 and the rejection threshold is 0.3,the accuracy rate can reach98%,the precision rate can reach 80%,the false alarm rate is only about 1.7%,and the missing alarm rate is only about 5%.The actual experimental results show that the detection results of this method can effectively find the abnormal rays in STEC observation data and the ground observation stations that produce more abnormal rays.(2)The CIT Experiment Based on RACR were carried out.Before the start of tomographic inversion,abnormal rays in the inversion area are detected and rejected by anomaly detection method,and only normal rays are retained to participate in the tomographic process.Experimental results of measured data show that,compared with MART algorithm,RACR has certain optimization according to the four methods of RMSE accuracy assessment,respectively 1)fo F2,2)hm F2,3)independent station STEC verification,and 4)ionosphere top electron density It can more accurately reconstruct the three-dimensional structure of the ionospheric electron density.