Advanced Synthetic Aperture Radar Interferometry Research Articles

Monitoring of recent ground surface subsidence in the Cangzhou region by the use of the InSAR time-series technique with multi-orbit Sentinel-1 TOPS imagery

ABSTRACTBy collecting 39 scenes of descending images and 26 scenes of ascending images of Sentinel-1 synthetic aperture radar (SAR), we monitored the ground subsidence situation of Cangzhou in China during the period from March 2015 to February 2017 with the advanced synthetic aperture radar interferometry (InSAR) time-series technique and obtained the time-series subsidence rates of Cangzhou. We then selected the two sets of results of the monitoring obtained during the same period (from July 2015 to December 2016) to verify the results’ accuracy, considering three overlapping areas (Xinhua District, Botou County, and Dongguang County). This analysis clearly indicated that both types of results have good consistency, and the maximum subsidence occurred in Dongguang County. By further study of the central area of Dongguang and the related urban development, we found that the subsidence reached about 80.0 mm over the study period and there was a close relationship between the subsidence trend and the main direction of the city development. Moreover, by combining the two sets of results, we confirmed that there has been subsidence of the high-speed railway line in the whole of the Cangzhou area, among which the most obvious subsidence has occurred in Dongguang and Qing Counties. Finally, it was proved that the Sentinel-1 data can be used to monitor ground surface subsidence, and the data are especially effective in identifying persistent scatterer points along a linear feature. Therefore, this article could provide reliable data to assist with important decisions about urban development projects in the Cangzhou area in the next few years.

Sentinel-1 InSAR data applied to surface deformation in Macaronesia (Canaries and Cape Verde)

The Macaronesia islands (Canary and Cape Verde archipelagos) have experienced intense seismic and volcanic activity that may in the near future put in risk people and goods. It is important to implement measurement strategies to monitor the seismic activity and the surface deformation. Synthetic Aperture Radar interferometry (SAR) has proven to be a useful technique to monitor the surface deformation in wide and remote areas, warning pre-eruption displacements and large-scale mass-wasting, so helping civil protection authorities. In this project, we investigate the applicability of SAR Interferometry (InSAR) for long time deformation monitoring in La Palma and Tenerife (Canary archipelago) and Fogo islands (Cape Verde archipelago). We have applied the advanced interferometric SAR processing based on Persistent Scatterers (PS). The small number of manmade structures on the volcanic areas reduces the density of Persistent Scatterers. Furthermore, the different ascending and descending acquisition geometries give different sets of PSs, with complementary spatial coverage and different line-of sight velocities. The strategy used to overcome the aforementioned problem is based on the combination of 3D GPS velocities with two sets of PS determined from ascending and descending passes. A data set of hundreds of SAR images acquired by Sentinel-1 were interferometrically processed and two sets of PSs, determined from ascending and descending passes, were computed for each island. The images were acquired between 2015 and 2018. In each island, the two PS datasets, were combined to derive the vertical deformation map and further be calibrated with GNSS velocities provided by EUREF continuous operating GNSS stations. The results are analysed and compared with previous results and studies of DInSAR techniques and GPS campaigns.

Monitoring and assessing reclamation settlement in coastal areas with advanced InSAR techniques: Macao city (China) case study

In the present study, we have investigated spatial-temporal behaviours of the land subsidence induced by reclamation activities in Macao Special Administrative Region, a coastal city of southern China. An advanced Synthetic Aperture Radar Interferometry (InSAR) technique, referred to as Interferometric Point Target Analysis (IPTA), was applied to retrieve the deformation rate and displacement time series during the period from July 2006 to March 2009. Validated by levelling survey measurements, the InSAR-derived results showed a fairly stable and homogeneous pattern within the land of Macao before 1912, which consists mainly of the three granitic islands of Macao Peninsula, Taipa Island and Coloane Island. In contrast, relatively large deformation rates (between − 15 and − 41 mm year − 1) and local spatial settlement variability were discovered within the latest reclamation areas. A quantitative comparison analysis of the relationship between the observed settlements and the evolution of land reclamation indicated a time-dependent settlement behaviour with respect to the age of the reclamation. Another key result was that differential settlements were detected over short distances in reclamation areas, particularly between the ground surfaces and the adjacent buildings, thus providing valuable information not only for early detection and remedial activities of potential settlement of such buildings but also for the design of future facilities adjacent to the buildings, particularly for that of large infrastructure developments.

Spatial and temporal deformation characteristics of marine alluvial deposits due to land reclamation: implications from InSAR observation and geotechnical estimate

AbstractGround deformation of reclaimed land is a key issue for reclamation design, construction and sustainable development in coastal areas as this consolidation process of the underlying compressible marine sediment sequences over very long‐time periods could lead to damage of both ground constructions and underground facilities. In this case study, we have investigated the spatial and temporal characteristics of residual reclamation settlement of Chek Lap Kok Airport, Hong Kong, one of the largest land reclamation projects worldwide. A total of 25 time series ENVISAT ASAR datasets, acquired between December 2003 and October 2008, were used to retrieve settlement rates and deformation history at high resolution and accuracy by means of advanced Synthetic Aperture Radar Interferometry (InSAR). The InSAR‐derived results show a fairly homogenous and stable pattern in the sectors of the airport site corresponding to the two original islands of Chek Lap Kok and Lam Chau. In contrast, a relatively high spatial settlement variability, ranging from moderate (3–7?mm/yr) to strong (>10?mm/yr) settlement rates, was discovered within the majority of the reclaimed portion of the airport. A joint analysis of InSAR observations and geological materials indicates that the variability of the recorded residual settlement was highly correlated with the variations of thickness and pre‐consolidation state of alluvial deposits below the reclamation. A quantitative comparison analysis also has been carried out between time series InSAR observations and theoretical estimates of residual settlement modelled by geotechnical investigations. The results imply that a primary consolidation process in alluvial deposits below the reclamation might be delayed with respect to the predicted results and may still have been occurring in most reclaimed areas during the investigation period (2003–2008); the time to complete it could stretch to decades depending on hydraulic conductivity and natural drainage conditions. Copyright © 2010 John Wiley & Sons, Ltd.