Precision Analysis of Terrestrial Reference Frame Parameters Based on EOP A-Priori Constraint Model

Earth Orientation Parameters (EOPs) are quantitative parameters that reflect the Earth spatial motion and its rates along the rotation axes. Precession and nutation parameters can be precisely described by the theoretical model, while the complex variation of the pole motion and LOD (length of day) is difficult to be modelled and hard to be predicted with high precision. With the development of Global Navigation Satellite System (GNSS), the spatial and temporal resolution of EOP products have been greatly improved. In GNSS data analysis, a-priori EOPs are normally used as the prediction from the IERS, and the constraint applied on a-priori EOP parameters has much impact on the estimates of GNSS solutions. This paper studies this impacts and develops an a-priori EOP constraint model. GPS data of 142 evenly distributed IGS stations from the beginning of 2010 to the end of 2015 are used for data analysis. Firstly, the precision of the pole motion, LOD and station coordinates under two mostly-used constraint conditions are compared and analyzed, which proves the impact of a-priori EOP constraint on GNSS solutions. Secondly, an a-priori EOP constraint model (pole motion composed of four periodical terms, while LOD composed of two periodical terms) is then developed, where the periodical terms are determined using the Least Square Spectrum Analysis (LSSA) approach. Lastly, the new model is used as the constraint conditions in GNSS solutions. Compared with above two mostly-used constraints, the pole motion and LOD parameters under the new constraint model is closer to the IGS products with largest improvement of 75%, which demonstrates that the new EOP a-prior constraint model can effectively improves the precision of GNSS parameters.