Measuring vertical ground displacement from São Paulo Line 2 subway perforation with PSInSAR and ICEYE data

Urban tunneling projects pose significant geotechnical challenges, especially in densely populated regions where heterogeneous subsurface conditions increase the risk of ground displacements. Monitoring these displacements is therefore essential to ensure infrastructure safety and minimize potential impacts on surrounding communities. Traditional geotechnical monitoring methods, such as ground-based sensors, achieve sub-millimeter precision with high temporal resolution but are limited in spatial coverage and incur high operational costs. In addition, they may interrupt construction activities and disturb neighborhoods, restricting their deployment to areas directly above critical infrastructure. This limitation often results in incomplete datasets and contributes to legal disputes over alleged tunneling-induced damage. This work investigates the application of Persistent Scatterer Interferometry (PSI) as a complementary technique for settlement monitoring in the expansion of São Paulo Metro Line 2. This large-scale project is expected to benefit approximately 1.2 million people, with a public investment of R$ 13.4 billion. The construction, which began in 2021, is being excavated in Paleogene sediments of the São Paulo and Resende formations of the São Paulo Basin, as well as Quaternary alluvial deposits. Owing to the rift-related tectonic heritage that originated this basin, the local geology is highly heterogeneous, which may result in differential settlement and further reinforces the need for comprehensive monitoring strategies.

Using high-resolution X-band images (1m resolution) from the ICEYE microsatellite constellation, this study employs SARPROZ to evaluate the dataset's coherence and baseline characteristics and assesses the potential of PSI for wide-area monitoring in a dense urban environment. The preliminary results demonstrated the significant challenges inherent in processing high-resolution X-band data from emerging constellations. Specifically, the large perpendicular baselines present in the dataset increased the sensitivity to topographic phase errors and geometric decorrelation, which, combined with strong atmospheric phase screen (APS) effects, hindered the isolation of the deformation signal through conventional linear phase modeling. These findings highlight the critical role of baseline optimization and advanced APS mitigation strategies when applying PSI to microsatellite constellations in tropical urban settings. Despite these constraints, this study provides valuable insights into the feasibility of integrating satellite-based SAR data with in situ monitoring for tunneling projects, offering a pathway toward more comprehensive, reliable, and cost-effective settlement monitoring frameworks to support informed decision-making in large-scale infrastructure development.