000005869 001__ 5869
000005869 005__ 20221027164455.0
000005869 0247_ $$2DOI$$a10.1007/s00190-022-01634-9
000005869 037__ $$aSCART-2022-0102
000005869 100__ $$aGobron, K.
000005869 245__ $$aImpact of offsets on assessing the low-frequency stochastic properties of geodetic time series
000005869 260__ $$c2022
000005869 520__ $$aUnderstanding and modelling the properties of the stochastic variations in geodetic time series is crucial to obtain realistic uncertainties for deterministic parameters, e.g., long-term velocities, and helpful in characterizing non-modelled processes. With the increasing span of geodetic time series, it is expected that additional observations would help better understand the low-frequency properties of these stochastic variations. In the meantime, recent studies evidenced that the choice of the functional model for the time series biases the assessment of these low-frequency stochastic properties. In particular, frequent offsets in position time series can hinder the evaluation of the noise level at low frequencies and prevent the detection of possible random-walk-type variability. This study investigates the ability of the Maximum Likelihood Estimation (MLE) method to correctly retrieve low-frequency stochastic properties of geodetic time series in the presence of frequent offsets. We show that part of the influence of offsets reported by previous studies results from the MLE method estimation biases. These biases occur even when all offset epochs are correctly identified and accounted for in the trajectory model. They can cause a dramatic underestimation of deterministic parameter uncertainties. We show that one can avoid biases using the Restricted Maximum Likelihood Estimation (RMLE) method. Yet, even when using the RMLE method or equivalent, adding offsets to the trajectory model inevitably blurs the estimated low-frequency properties of geodetic time series by increasing low-frequency stochastic parameter uncertainties more than other stochastic parameters.
000005869 536__ $$a2BRAIN_LASUGEO/$$c2BRAIN_LASUGEO/$$f2BRAIN_LASUGEO
000005869 594__ $$aNO
000005869 6531_ $$aOffsets
000005869 6531_ $$aVariance component estimation
000005869 6531_ $$aMaximum likelihood estimation
000005869 6531_ $$aVelocity uncertainty
000005869 700__ $$aRebischung, P.
000005869 700__ $$ade Viron, O.
000005869 700__ $$aDemoulin, A.
000005869 700__ $$aVan Camp, M.
000005869 773__ $$n46$$pJournal of Geodesy$$v96$$y2022
000005869 8560_ $$fmichel.vancamp@observatoire.be
000005869 85642 $$ahttps://doi.org/10.1007/s00190-022-01634-9
000005869 905__ $$apublished in
000005869 980__ $$aREFERD