Antenna environment effects on linear combination phase residuals: Pattern types and a novel metric

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.