Analysis Method Of GNSS Datum Station Elevation Time Series Based On Entropy Theory

The coordinate time series of accumulated observation of satellite navigation and positioning reference station is the basis of Geodesy and geodynamics,and plays an important role in the establishment of global velocity field model and the analysis of plate motion law.The vertical coordinate sequence not only contains a lot of noise,but also has obvious periodic changes.It has a certain scientific and practical value to extract the effective information from the elevation sequence.In this paper,the height time series data of 12 stations in the world in recent 20 years are taken as the research object,and the entropy theory mathematical method and adaptive method are used to analyze the characteristics of the height time series of stations.1)An improved noise adaptive ensemble empirical mode decomposition method is proposed based on distance evaluation function and entropy clustering algorithm.The problem that the traditional ensemble empirical mode decomposition method can not completely eliminate the influence of random noise,which reduces the signal-to-noise ratio of decomposition and affects the effect of signal reconstruction is improved.The experimental results show that the proposed method improves the SNR by more than 3.2%,improves the decomposition accuracy by more than 2.3%,reduces the root mean square error of reconstructed signal by more than 9.4%,and reduces the influence of adding random noise on time series decomposition and signal reconstruction.2)A quantitative identification method of nonlinear trend term based on permutation entropy is proposed.Three models are used for quantitative analysis of nonlinear trend term,and four power spectrum analysis methods are selected for periodic test of time series.The results show that the method avoids the human error and effectively identifies the nonlinear trend term of the sequence.Among the three models,the Fourier model has the best fitting effect.The maximum entropy spectrum analysis method can accurately identify the main period of the sequence,and the curve is smoother,less side lobe and smaller main lobe width.3)Based on the results of linear least squares,the nonlinear model of periodic term is established,and the noise in the station is analyzed by using the improved maximum likelihood estimation method.The experimental results show that the nonlinear motion model is closer to the actual motion law of the station in the elevation direction than the linear motion model,and each station shows different periods and motion forms;the optimal noise model of the time series of the elevation coordinates of the satellite navigation and positioning reference station is white noise + flicker noise,and the amplitude of flicker noise is greater than that of white noise.This paper includes 23 figures,15 tables and 70 references.