Wide-area coastal deformation extraction using multi-path/frame InSAR: A case study of the Bohai Rim

Coastal areas worldwide experience serious ground subsidence and rising sea levels, leading to frequent flooding and continued elevation loss. Reliable estimation of coastal subsidence is critical for effective risk assessment and management. Interferometric Synthetic Aperture Radar (InSAR) enables millimeter-scale deformation monitoring, but generating seamless wide-area results remains challenging due to limited swath width and inconsistencies between adjacent frames. This study proposes an adaptive gridded adjustment model for merging multi-path/frame InSAR results into a wide-area high-precision deformation map. We employ a quadtree-based adaptive grid with dynamically optimized sizes determined by the deformation gradient. The gridded corrections are combined with GNSS-constrained global corrections to eliminate inter-frame biases. Applied to the coastal area of the Bohai Rim, this method reduces the Sentinel-1 discrepancies by 38 %, and outperforms the fixed-grid method in achieving an optimal balance between precision and efficiency. This method is useful for wide-area high-precision deformation monitoring to support risk assessments of relative sea level rise in the context of global climate change.