GNGTS 2015 - Atti del 34° Convegno Nazionale

GNGTS 2015 S essione 1.2 97 reliable estimation of: average velocity, amplitude and periods of seasonal signals and noise the time series of the three position components are analysed with the same procedure as described in Cenni et al. (2012, 2013). This procedure is subdivided into the following five steps: 1 data cleaning: time series have been preliminarily analyzed in order to detect and remove outliers. We have considered as outlier the data with value or associated uncertainties greater than 3 times the weighted root mean square (wrms) of the series. The outlier epochs have been identified separately in each coordinate direction and then applied to all three components; 2 preliminary estimation: the time pattern of the daily position component y 1k ( t ) ( k 1, 2, 3, for the north, east and vertical component) has been modelled by the following relation: (1) Fig. 1 – Locations of the permanent GPS stations used in this work. The colour of the circles indicate the observation time span of each single site considered, following the chromatic scale on the right. The inset shows the 13 IGS stations we have used to align the network here analyzed to the ITRF2008 reference frame (Altamimi et al., 2012) and the common stations used in the distributed procedure.