Quality assessment of the Topo-Iberia CGPS stations and data quality's effects on postfit ionosphere-free phase residuals

This paper analyzed GPS data from the Topo-Iberia network spanning almost 12 years (2008–2020). The data quality information for all 26 Topo-Iberia stations is provided for the first time, complementing the Spanish Geological Survey's storage work. Data analyses based on quality indicators obtained using TEQC have been carried out. The guidelines and data quality information from the IGS stations have been considered as the quality references, with the stations ALJI, EPCU, and TIOU standing out as the worst stations, while on the contrary, FUEN, PALM, PILA, and TRIA meet the quality requirements to become an IGS station. The relationship between the GPS data quality and their GAMIT- and GipsyX-derived postfit ionosphere-free phase residuals has also been investigated, and the results reveal an inversely proportional relationship. It has been found that the stations showing an increase in elevation of the horizon line, also show an increase in cycle slips and multipath, are among the poorest quality stations, and among those with the highest postfit RMS of phase residuals. Moreover, the evolution of the vegetation around the antenna should be considered as it could cause a progressive loss of quality, which is not complying with the IGS standards. The quality assessment shows that the Topo-Iberia stations are appropriate for geodetic purposes, but permanent monitoring would be necessary to avoid the least possible loss of data and quality. In addition, a method to characterize the GNSS data quality is proposed.