Interferometric Synthetic Aperture Radar (InSAR) uses the phase difference between satellite radar images to infer tiny ground deformations. Among the techniques, DInSAR, PS-InSAR, and SBAS-InSAR are three common and complementary methods: DInSAR suits large-area, event-driven rapid deformation assessment; PS-InSAR delivers point-wise, millimeter-level long-term time series over stable reflectors such as urban areas and structures; SBAS-InSAR uses multi-epoch small-baseline processing to reduce decorrelation, making it suitable for vegetated areas or terrain with strong surface change. The following explains the principles, differences, and how to choose among them.
Quick Comparison
| Item | DInSAR | PS-InSAR | SBAS-InSAR |
|---|---|---|---|
| Full name | Differential InSAR | Persistent Scatterer InSAR | Small Baseline Subset InSAR |
| Accuracy | Centimeter-level | Millimeter-level (point-wise time series) | Millimeter-level (areal time series) |
| Images required | Few (2 epochs suffice) | Many (tens or more) | Many (tens or more) |
| Suitable areas | Large bare-ground surfaces | Urban areas, bedrock, structures | Vegetation, farmland, deforming terrain |
| Deformation type | Event-driven, large magnitude | Long-term, slow, point-wise | Long-term, areal |
| Computation cost | Low | High | High |
| Typical use | Coseismic deformation, large landslides | Urban subsidence, buildings and bridges | Land subsidence, landslide-prone areas |
How Each Technique Works
DInSAR (Differential InSAR)
DInSAR interferes two (or a few) radar images and removes the topographic phase to obtain line-of-sight (LOS) deformation. Its advantage is that few images are needed and computation is fast, allowing rapid assessment of large-area deformation right after an event; its drawback is sensitivity to atmospheric delay and temporal/spatial decorrelation, making it hard to detect long-term, slow, millimeter-level deformation. It suits larger-magnitude events such as coseismic deformation, large-scale landslides, and volcanic activity.
PS-InSAR (Persistent Scatterer InSAR)
PS-InSAR searches a long time series of images for phase-stable “persistent scatterers” (building corners, bare rock, man-made structures) and builds a time series for each point, reaching millimeter-level accuracy. Its strength is in urban and structure-dense areas, but it fails in vegetated areas that lack stable reflectors. It suits long-term point-wise monitoring of urban subsidence, buildings and bridges, levees and infrastructure, with artificial corner reflectors (CR) added where needed.
SBAS-InSAR (Small Baseline Subset InSAR)
SBAS-InSAR selects image pairs with small temporal and spatial baselines to form subsets, reducing decorrelation, and reconstructs the deformation time series in an areal manner. Compared with PS-InSAR, it performs more reliably over vegetated areas, farmland, and strongly deforming terrain, yielding a more continuous deformation field. It suits large-area areal monitoring such as land subsidence, landslide-prone areas, and catchments.
How to Choose
Work through the following questions step by step:
- Is it event-driven, large-magnitude deformation requiring rapid assessment? → Yes, choose DInSAR.
- Are the targets stable reflectors such as urban areas, structures, or bedrock, needing point-wise long-term time series? → Yes, choose PS-InSAR.
- Is the area vegetated or strongly deforming, needing an areal long-term deformation field? → Yes, choose SBAS-InSAR.
- Need both wide-area coverage and focused accuracy? → Use InSAR for wide-area screening to identify hotspots, then GNSS for real-time monitoring of key locations.
In practice the three are often combined: first screen a large area with InSAR, then validate and track in real time with field monitoring.
Application in Taiwan
InSAR is already widely applied in Taiwan for wide-area monitoring of large-scale landslide-prone areas, land subsidence, and urban settlement. RST Ltd. provides complete InSAR satellite radar deformation analysis, and can integrate GNSS and field sensor data.
FAQ
Q: Does InSAR monitoring require installing equipment on site? No. DInSAR, PS-InSAR, and SBAS-InSAR are all remote monitoring techniques using satellite radar imagery; acquiring imagery of the target area is enough to perform the analysis.
Q: Can the three methods be used together? Yes, and they often are. First lock down the area with DInSAR / wide-area screening, then build long-term time series with PS / SBAS, adding GNSS field validation where needed.
Q: In which direction does InSAR measure deformation? InSAR measures deformation in the satellite line-of-sight (LOS) direction; combining ascending/descending orbit data or GNSS resolves the vertical and horizontal components.
Need help choosing the right InSAR method for your monitoring requirements? Feel free to contact RST Ltd..