The Sinking Ho Chi Minh Megacity by Radar Interferometry

An advanced persistent scatterers and distributed scatterers (PSDS) SAR Interferometry algorithm has been implemented as an open-source TomoSAR package to analyze subsidence in Ho Chi Minh City, Vietnam’s largest city. This study presents the first examination of both the horizontal East–West and vertical components of subsidence in this region using multigeometry Sentinel-1 TomoSAR technology. The correlation between the reference leveling velocity and the estimated PSDS results is $R^{2} = 0.98$, with a root mean square error of 4.4 mm/year, indicating a strong agreement. Both C-band Sentinel-1 and X-band COSMO-SkyMed data reveal the same vertical subsidence pattern, aligning with previous work from L-band PALSAR. Key findings include improved vertical velocity estimations, with precision enhanced by up to 3 mm/year by incorporating horizontal motion, and significant horizontal velocities detected in the city’s western area. These results demonstrate the effectiveness of Sentinel-1 data for subsidence monitoring in Southeast Asian urban environments and highlight the importance of advanced processing techniques that include atmospheric and phase unwrapping corrections. The research provides valuable insights for urban planners and policymakers who are addressing subsidence risks in rapidly developing cities.