Analysis on the Representation of Polar Motion in GNSS Applications

In modern technology, the daily polar motion parameters are estimated with the orbit parameters in the precise orbit determination process. So, the precision of polar motion parameters affects that of orbit parameters as well as the reference frame. During current estimations, both the x-pole and y-pole are represented by a linear model. However, controversial of using the offset and rate model or the piecewise linear model remains unsolved. In this article, the behavior of polar motion is studied and simulated, then estimated using both models mention above. The attempt of implementing the least square cubic spline (LSCS) model is realized, and the comparison of these models are conducted. Consequently, the LSCS model revealed a significant improvement in the sense of residuals with the simulated polar motion data with less parameters per estimation period compared to the traditional offset and rate model. Furthermore, hypothesis testing show that higher order parameters are significant. It is then worth studying how much will the LSCS model affect orbit parameters.