Abstract: In response to the issues of traditional urban ground subsidence monitoring often relying on a single monitoring method such as InSAR/GNSS,the use of post-processing strategies for GNSS results,and the high costs of imported GNSS receivers,this paper utilizes synergistic monitoring with InSAR and universal GNSS,proposing a high-precision near-real-time calculation model based on universal GNSS.By processing Sentinel-1A data from June 2015 to June 2024 using time-series InSAR technology and universal GNSS data from June 2023 to September 2024 with near-real-time calculation technology,the study obtained average deformation results over nearly a decade for Xi'an,deformation along the subway line within a 1 km buffer zone,and a high-precision three-dimensional near-real-time deformation sequence.The three-dimensional GNSS deformation was projected to the line of sight (LOS) for comparison with InSAR results.The results show that:①The overall ground deformation in Xi'an has gradually stabilized from subsidence,mainly influenced by groundwater as revealed by wavelet analysis; ②The deformation at points along the subway line is highly consistent with the period of subway construction,suggesting that underground engineering may be an important factor affecting ground subsidence in Xi'an;③The near-real-time LOS results from four GNSS stations exhibit a maximum deviation of within 1.2 cm compared to InSAR,with average deviations of 3.1,3.61,6.62,and 3.59 mm respectively,demonstrating that near-real-time calculation with universal GNSS can meet the vast majority of conventional deformation monitoring needs.

Key words: urban ground subsidence, time-series InSAR, universal GNSS near real-time solution, deformation along the subway line