Study On Influencing Factors Of GNSS Coordinate Time Series Noise Model Establishment

Existing research shows that GNSS coordinate time series show significant nonlinear changes,these nonlinear changes mainly reflect that the stations are subjected to geophysical effects such as non-tidal ocean load,hydrological load,atmospheric load and so on.Studying on the noise model of GNSS coordinate time series especially the influence of non-linear motion on the noise model can obtain accurate and reliable GNSS reference station velocity,and it provide basic data for research and application such as plate motion,updating and maintenance of the earth reference frame and monitoring geotectonic deformation process which is of great significance.In this paper,the data of 239 GNSS reference stations around the world from 2006 to 2013 are taken as the research object to study the influence of nonlinear changes on noise model estimation with GNSS coordinate time series.The main contents of this paper are as follows:Study the influence of environmental loading on noise model establishment.A wider range of noise models,e.g.White Noise plus Random Walk Noise(WN+RW),White Noise plus Flicker Noise(WN+FN),White Noise plus Flicker Noise plus Random Walk Noise(WN+FN+RW),White Noise plus Power Rate Noise(WN+PL))are used to analyze the optimal noise model of GNSS coordinate time series before and after environmental loading correction.The results show that more than 99% of the optimal noise models of GNSS reference stations have changed,Besides,after the loading correction,the estimated GNSS station velocity uncertainty and annual amplitude values increase.Study the influence of common mode error on noise model estimation for the residual sequence of coordinates after loading correction.The principal component analysis method is adopted to spatially filter on the GNSS coordinate time series,to separate the common mode error,then the noise analysis is carried out on the residual GNSS coordinate time series.The results show that the common mode error will cause biased estimation to the noise model,and the influence is greater in the horizontal direction than in the vertical direction.If the common mode error is not removed from the coordinate time series,the velocity value of GNSS reference station will be overestimated.An ETS corrected GNSS coordinate time series model based on exponential logarithmic modeling.Studies on the effects of ETS(Episodic Tremor and Slip)on the construction of optimal noise model and station velocity.Firstly,Exponential and logarithmic algorithm are used to model the process of Episodic Tremor & Slip.Then the ETS-corrected GNSS coordinate residual time series is obtained with the model.Finally,we make performance analysis on the GNSS time series before and after ETS correction.The results show that ETS will cause the change of GNSS coordinate time series noise model(a biased estimate of the noise model).Secondly,the effects of different intermittent ETS parameters on noise model establishment and velocity estimation are discussed.The results show that different ETS parameters have little effect on the noise model and station velocity estimation.