Land subsidence in Jakarta in Three Dimensions (2014-2025) using InSAR-GNSS Datum Connection and the Strapdown Decomposition

Alexandru Mihai Lapadat, Heri Andreas, Wietske S Brouwer, Simon van Diepen, Dhota Pradipta, Ramon Hanssen 

Several coastal megacities face compounding hazards from rising sea levels and land subsidence. Jakarta, one of the fastest-sinking megacities, already experiences recurrent flooding amplified by rapid land subsidence. However, Jakarta's three-dimensional (3D) ground-surface motion has remained poorly resolved due to sparse ground-based geodetic observations and the line-of-sight (LoS) limitation of conventional InSAR observations. Assessing and mitigating this hazard requires reliable estimates of three-dimensional ground motion over wide spatial and temporal scales in a well-defined geodetic reference frame and datum. Here we combine spaceborne InSAR and GNSS measurements to align multi-track InSAR LoS datasets between 2014 and 2025 to a common datum for unbiased three-dimensional velocity decomposition, and connect the resulting velocity field to the SPFF using GNSS. This yields a spatially extensive 3D characterization of Jakarta’s ground-surface motion on a 450 × 450 m grid in a globally consistent reference frame. Our results show that Jakarta’s land motion is dominated by several distinct subsidence bowls, with subsidence and directional horizontal rates of up to −7.9 cm/yr and 1.7 cm/yr, respectively, superimposed on slow regional subsidence of −0.9 cm/yr across the metropolitan area. The resulting 3D velocity field, including its variance–covariance information, is publicly available as a reference dataset for ground-deformation studies in Jakarta. Given that only one continuous GNSS station provides sufficient temporal overlap with the InSAR observations for the datum connection, we recommend installing dedicated geodetic ground-based infrastructure to ensure robust and sustainable monitoring in the future.