The IGS contribution to ITRF2013

Eight IGS Analysis Centers (ACs) have completed, or are about to complete, a second reanalysis campaign (repro2) of the GNSS data collected by the IGS global tracking network back to 1994, using the latest available models and methodology. The AC repro2 contributions comprise in particular daily terrestrial frame solutions including station coordinates and Earth orientation parameters. Once all AC contributions are available, the AC daily terrestrial frame solutions will be combined by the IGS Reference Frame Working Group. The IGS daily combined solutions will form the IGS contribution to the next release of the International Terrestrial Reference Frame (ITRF2013).

The methodology used for the IGS repro2 terrestrial frame combinations will first be introduced. A particular focus will be on the detection and mitigation of the inter-AC station position biases, such as those evidenced in the combination residuals from the first IGS reprocessing campaign.

We will then discuss results from the repro2 combinations. The repro2 combination residuals will in particular constitute a valuable dataset for the characterization and understanding of the systematic errors affecting GNSS station position estimates. We will therefore examine the spatio-temporal evolution of the AC residuals, and in particular the distribution of spurious periodic signals at harmonics of the GPS draconitic year.

We will finally present the stacking of the IGS daily combined solutions into the long-term GNSS terrestrial frame that will enter the ITRF2013 computation. Our focus will be on the methodological advances made since the ITRF2008 computation (detection of jumps in station position time series; modelling of non-linear station motions).