| Popis: |
The basic concept of establishing linear velocity field with fixed period term in CORS stations height time series is described, and the problem of deviation between given period and actual period is pointed out. Therefore, this paper proposes a nonlinear velocity field modeling method for CORS stations height time series. This method takes the linear least squares solution as the initial value of iteration, and uses the gauss-newtoni-teration algorithm to solve the unknown parameters of the nonlinear velocity field model, realizing the nonlinear fitting of height time series data of CORS stations. The test method for the heteroscedasticity of the residual square sequence of the fitting model is given, and the basic criteria for the establishment of GARCH (p, q) model to reflect the fluctuations of non-stationary sequence are expounded. The six CORS stations at home and abroad more than 20 years as the research object, the height of time series nonlinear velocity motion model is set up, the results show that the CORS stations height movement does not exist strict year or half year cycle, the approximate periodic motion is most obvious, the approximate period of two years than the minimum, cycle in deviation of 12%, half year cycle is 18%, two year period is 6%, nonlinear modeling accuracy and effect is better than the linear model as a whole. The ARCH test method is used to obtain the heteroscedasticity of the residual square sequence of the nonlinear model of CORS stations height, that is, the residual square sequence has non-stationary characteristics. GARCH (p, q) model is introduced to model the non-stationary residual square sequence of the height component of CORS stations, which reflects the non-stationary fluctuation of the residual square sequence. The feasibility of GARCH (p, q) model in modeling non-stationary residual square series of CORS stations height is verified, which provides an idea for future modeling of non-stationary noise series of CORS stations height and reconstruction of nonlinear velocity field with GARCH (p, q) model. |
