Development of an Interferometric Mass Processing Chain for Multitemporal Ground Deformation Measurements

The main goal of the RESIST project is to understand the mechanisms driving volcanic eruptions and landslides in the Kivu region, on the East African Rift. In order to model both volcanic and landslide processes, it is necessary to measure ground deformations in the region accurately. For this purpose, both ground-based instruments (e.g. GPS network) and spaceborne data (e.g. optical and SAR images) are used.
One aspect of the project focuses on Differential SAR Interferometry (DInSAR), which is a technique used to map ground deformations occurring between two SAR images acquired at different times. It is today a well-mastered technique that offers large spatial coverage with a typical temporal sampling of one to several days, depending on the chosen sensor. In the last years, multitemporal approaches based on DInSAR have been developed, like the Small BAseline Subset (SBAS) [1] and Multidimensional Small BAseline Subset (MSBAS) [2] techniques, or the Persistent Scatterers Interferometry (PSI) [3]. In the framework of RESIST, we use MSBAS to perform ground deformations monitoring along time.
The Multidimensional Small BAseline Subset (MSBAS) technique produces 2-D time series of ground deformations by integrating data sets of SAR images acquired by different sensors, with different spatial and temporal sampling, resolutions, incidence angles, wavelengths, pass directions and other varying parameters. By combining at least two data sets with overlapping spatial and temporal coverage and an extended range of look angles, the evolution of deformations in the vertical and west-east directions can be computed by the MSBAS approach [2].
The MSBAS software feeds on a large amount of deformation maps, which are produce by DInSAR. Such an amount of data cannot be produced by hand and that is the reason why we developed an automatic interferometric processing chain meant to produce large amounts of products adequate for multitemporal methods like MSBAS.
The interferometric processing is supported by the CSL InSAR Suite (CIS) software developed at Centre Spatial de Liège, which presents the advantages to be fully adaptable to the needs of the MSBAS technique and the thematic specificities. Indeed, numerous options (e.g. adaptive filtering, wide swath interferometry) have been added to the CIS software in the framework of the RESIST project.
In a first time, we will briefly present the MSBAS approach and its advantages regarding the ground deformation measurements. In the second part of the presentation, we will introduce the mass processing chain step by step and its functionalities. Critical steps of the chain, like the chosen strategy for the interferometric pairs selection, the integration of Sentinel-1 data or the image interpolation approach, will be presented in more details. Finally, preliminary results of an MSBAS processing over the Bukavu area will be presented.

REFERENCES:

[1] Berardino, P., Fornaro, G., Lanari, R., and Sansosti, E. (2002). A new algorithm for surface deformation monitoring based on small baseline differential SAR interferograms, IEEE Trans. Geosci. Remote Sens., 40, 11, pp. 2375-2383. doi: 10.1109/TGRS.2002.803792.
[2] Samsonov, S., and d’Oreye, N. (2012). Multidimensional time series analysis of ground deformation from multiple InSAR data sets applied to Virunga Volcanic Province, Geophysical Journal International, 191, 3, pp. 1095-1108. doi: 10.1111/j.1365-246X.2012.05669.x
[3] Ferretti, A., Prati, C., and Rocca, F. (2001). Permanent scatterers in SAR interferometry, IEEE Trans. Geosci. Remote Sens., 39, 1, pp. 8-20. doi: 10.1109/36.898661.