The use of ground-based GNSS data for climate research is an emerging field. The reprocessing activity under EUREF has been a huge effort, generating homogeneous tropospheric products to be used as a data set for monitoring trends in atmospheric water vapour. EPN-Repro2 data have been evaluated against RS and ERA-Interim data as well as in terms of ZTD trends. The obtained results show that they can be used for ZTD trend detection over Europe in areas where other data are not available.

In this paper two official processing strategies of GPS observations were analysed. The main purpose was to assess differences in long-term (linear trends) and short-term (oscillations) changes between these two sets of data. Investigation was based on 18-year and 16-year time series and showed that, despite the general consistency, for selected stations a change of processing strategy may have caused significant differences (compared to the uncertainties) in estimated linear trend values.