Estimation of the Data Precision Using Variance Component Estimation, with Application to Polar Motion Time Series

The precision assessment of Earth rotation fluctuations is of fundamental importance for internal geophysics: for example length-of-day (LOD) studies allow to better understand the long-term core dynamics, nutation allows to determine fundamental properties of the core and inner core , and polar motion studies contribute to a better knowledge of the mantle visco-elastic response . To obtain the full benefit from each data set, it is necessary to assess its precision before interpreting it geophysically. Most of the time, precision assessment of geodesy data is achieved by comparing independent observations of the same quantity, as done for example with the three-cornered hat (TCH) method. We propose to addapt the Variance Component Estimation (VCE) method to assess the data precision, and we show that it outperforms the TCH in the same configuration. We also show how VCE can be used to estimate a confidence interval for the precision assessment. This method is then applied to Polar Motion data.