This study investigates the relationship between elevation angle-dependent mean (elmean) ionosphere-free phase residuals and the antenna environment in permanent GNSS stations, as well as the noise of their supporting monuments, including seasonal variations. Residuals and noise values were derived from GAMIT/GLOBK processing of continuous GPS data over a multi-year period. The pattern formed by the trace of the elmean residuals is influenced by characteristics of the antenna environment, enabling the identification of five distinct pattern types. A diagram of these pattern types is presented for the first time and may serve as a useful tool for selecting optimal GNSS antenna environments. Additionally, a novel metric is proposed: the difference index of the phase residual pattern (PRPDI), which effectively detects changes in the antenna environment and distinguishes stations with the best- and worst-quality data. The highest PRPDI values correspond to the lowest-quality stations and those exhibiting changes in the occlusion horizon. The smallest elmean residuals were found in environments with uneven terrain and vegetation cover, while the largest residuals were found in environments associated with monuments located on flat building roofs. Noise analysis indicates that stations with standard pillars on bedrock and shallow-drilled braced monuments exhibit lower noise levels than those with small pillars or building-mounted monuments, consistent with previous findings. Seasonal noise correlates with the antenna environment but shows no dependence on geographic location. These findings, based on data from the Topo-Iberia network, highlight the potential of the proposed methods and metrics to improve GNSS network performance.

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.