Daqing Ge

Integrating medium and high resolution PSInSAR data to monitor terrain motion along large scale manmade linear features- a case study in Shanghai

We present in this work the monitoring of terrain displacement along large scale manmade linear features in Shanghai city by integrating medium and high resolution PSInSAR data. Focused on the stability of linear features themselves and infrastructures over the path of linear features, land subsidence along Shanghai Magnetic Levitation (Maglev) and No. 10 subway tunnels have been investigated. In the first case we reported the impact of regional subsidence to Maglev line by analyzing PSInSAR measurements from ENVISAT ASAR data and Cosmo 3m resolution data. Subsidence velocity map derived through Cosmo data indicates that the Maglev line has slightly displacement although regional subsidence rate reaches 2-3 cm per year described by ENVISAT data. The second case dedicated on the assessment of subway tunnels to buildings over the path of No. 10 subway. By time series analysis of the Cosmo SAR data acquired during Nov 2008 to June 2010, terrain subsidence in the construction period and operational period of No. 10 line has been studied. The PSInSAR data demonstrated that subsidence caused by subway tunnels reaches l-2cm and it is accelerated after the running of subways since the dynamic loading effect of vehicles.

Mapping urban subsidence with TerraSAR-X data by PSI analysis

With a spatial resolution of up to 1 m, the German radar satellite TerraSAR-X has significantly improved the applicability of spaceborne SAR interferometry (InSAR) technique for fast ground motion monitoring due to its high spatial resolution and short time interval. In this work we present the first Permanent Scatterer Interferometry analysis with TerraSAR-X data for urban subsidence mapping in Tianjin city in China. Totally 17 scenes strip mode SAR images have been collected from Feb to Oct 2009 to perform the PSI analysis. The resulted average subsidence velocity demonstrates the ability of high resolution data for detailed monitoring of urban subsidence. Comparison between PSI result of TerraSAR-X and ENVISAT show the potential of TerraSAR-X data for urban motion as well as large scale manmade linear infrastructure monitoring.

Large scale land subsidence monitoring with a reduced set of SAR images

In this work we presented the first experimental results of land subsidence mapping for large areas by using Coherent Point Target SAR interferometry with a reduced set of images in the North China Plain (NCP). Since the limitations of the classical Permanent Scatterer InSAR (PSI) for short temporal span surface deformation monitoring due to the dependency on large volumes data availability, we combine the classical PS InSAR and Small Baseline Subset (SBAS) technique in the data processing chain for large coverage InSAR data processing with a reduced set images. The starting point of our study is the generation of small baseline interferograms of the continuous frames in the same track. Following that, each stack of interferograms are processed with CPT InSAR so as to minimize the effect of phase ramp caused by inaccuracy baseline estimation. For large scale land subsidence mapping, all the mean velocity map are merged into a long strip and the subsidence rate of each coherent point are retrieved. The algorithm are tested with 15 ENVISAT ASAR images collected during the period from Jun, 2007 to Nov, 2008 with an extent of 100 × 400km2 in the NCP for land subsidence mapping. The presented results indicates the large scale land subsidence in central NCP and demonstrates the effectiveness the approach.

Land Subsidence Investigation Along Railway Using Permanent Scatterers SAR Interferometry

Land subsidence is a common geohazards in many countries of the world, which cause damages for many urban areas and civil infrastructure. The development of spaceborne SAR interferometry provides an efficient tool for large spatial scale surface deformation monitoring with a high accuracy and precision. This paper presents a case study of land subsidence investigation along railway by using Permanent Scatterers SAR interferometry (PSI). Based upon the conventional InSAR techniques, PS-InSAR overcomes atmospheric delay anomalies and temporal and geometric decorrelation by exploiting the temporal and spatial characteristics of radar interferometric signatures collected from point-wise targets that preserve phase coherent over time. In this work, a linear model is adopted to retrieval land subsidence rate by using the differential phase series of the permanent scatterers. For the subsidence rate derivation along the railway, a buffer with a width of 10 km is set up and those PS within the buffer is interpolated to generate the subsidence map. The results archived using ENVISAT ASAR images acquired from 2003 to 2004 are validated with the precise leveling data and used to investigate the Jing-Jin railway in north china.

Merging multi-track PSI result for land subsidence mapping over very extended area

The Permanent Scatterer Interferometry (PSI) technique is usually applied for surface deformation mapping at local area from 1 up to a maximum of 100 km2. Although the ability to provide deformation map of regional area exceeding 10,000 km2, the processed area of interest is mostly limited to SAR acquisitions in a single satellite track and frame. In this work we present the study of merging multi-track PSI results for land subsidence monitoring over very extended area. Apart from the description of the PSI method used for long strip SAR data processing, datum connection of multiple adjacent tracks, including conversion of a common coordinate system and the connection of the PSI derived velocity maps are demonstrated. The application of the proposed method to monitor large coverage land subsidence in the central North China Plain (NCP) is described. The presented results obtained by merging 3 adjacent tracks of ENVISAT ASAR data acquired between Jan, 2007 and Dec, 2009, with a coverage of 200×260km2 are very significant and indicate the effectiveness and potential of this technique for land subsidence mapping over very extended area.

PSI analyses of land subsidence due to economic development near the city of Hangzhou, China

In this work we mapped the spatial and temporal patterns of the land subsidence near the city of Hangzhou, China by PSI analysis with 49 scenes of ERS-1/2 SAR images acquired from 1992 to 2006 to detect and retrieve the subsidence due to economic development. The main reason of land subsidence in Hangzhou is groundwater exploitation, which is necessary for the rapid economic development, especially in China. Xiaoshan Economic and Technological Development Zone was approved as a state-level development zone by the State Council in May, 1993. Since then the zone has been suffering land subsidence. There have been more than 300 overseas-funded enterprises with investors from 26 countries and regions by the year 2006. The development of this area can be divided into three periods according to its pace: construction period (1993-1996), stable increase period (1996-2001) and high-speed period (2001-2006).

Monitoring Urban Subsidence in the City of Tianjin (China) by Differential SAR Interferometry

Using ASAR images covering the period from April 2003 to August 2004, we show that ENVISAT SAR Interferometry can provide us valuable information to map the subsidence phenomena of Tianjin area. The approach of interferogram stacking has been used in order to reduce the influence of the atmospheric fluctuations on the deformation estimation. In the process of removing topographic component from the inerferometric images, SRTM DEM are used. The geoid height in the area has been compensated. In the stage of unwrapping, the coherence values of pixels in the interferograms are taken into consideration and the method based on the minimum cost flow algorithm and the triangulation of sparse points are used. KeywordsDInSAR; subsidence; urban area

Seasonal subsidence retrieval with Coherent Point Target SAR Interferometry: A case study in Dezhou city

Spaceborne Radar Interferometry (InSAR) is well known as an accurate, time saving and low cost technique for monitoring of surface deformation phenomena ranging from land subsidence, volcano displacement, tectonic motion and even slow landslides. The Coherent Point Target SAR Interferometry (CPT-InSAR) overcomes atmospheric delay anomalies and the temporal and geometric decorrelation by the interferometric calculating of point-wise targets which maintain high coherent. The linear and no-linear subsidence can be retrieved by CPT-InSAR, which can be done well even with less than 20 SAR images by integrating the SBAS (Small Baseline Subset) and PSI (Permanent Scatterers InSAR) techniques. The application of the proposed method to monitor seasonal land subsidence in the Dezhou city, a medium city in Shandong province in North China Plain (NCP), is described. The presented results, obtained by processing of ENVISAT ASAR data acquired between Mar, 2004 and Dec, 2008, are highly agreed with the deep groundwater level, including the spatial position and variation tendency.

Monitoring urban subsidence with coherent point target SAR interferometry

Spaceborne SAR interferometry (InSAR) is a well known microwave remote sensing technique which has been applied for topography mapping and ground motion monitoring by exploiting phase difference from SAR data acquisition with relevant large spatial scale and high precision. The developed Permanent Scatterers Interferometry (PSI) is a further step of InSAR technique which offers a convenient processing framework that enables the use of all data acquisitions. It aims to bypass the problem of geometric and temporal decorrelation by considering long term coherent point. Furthermore, by using a large number of data, atmospheric signal is estimated and compensated for. We present in this work the development of an improved PSI, called Coherent Point Target InSAR, for land subsidence velocity field estimation in urban area as well as rural area in China. A series of case studies demonstrate the ability of CPT InSAR for monitoring ground subsidence felid with relevant large spatial extent as well as small area.

Surface Subsidence Monitoring with Coherent Point Target SAR Ineterferometry

In this paper, an improved approach for surface subsidence monitoring with SAR interferometry by using coherent point target is presented. A joint criterion of amplitude dispersion index and high spectral correlation criterion are proposed for coherent point target identification, which enable a flexible target selection in case of small or large volume of SAR data. Further more, in order to avid the decorelation caused by long temporal or spatial baseline, interferogram stack are generated from the combination of those images with a small baseline. For subsidence rate calculation, a spatial and temporal regression is exploited to unwrap the differential phase of each coherent point target and a linear model is adopted for the estimation of deformation parameters. Case studies in two different test sites demonstrate the advantage and limitations of the algorithm.