How to avoid false interpretations of Sentinel-1A TOPSAR interferometric data in landslide mapping? A case study: recent landslides in Transdanubia, Hungary

• Published in: Natural hazards (Dordrecht) 2019-03, Vol.96 (2), p.693-712
• Main Authors: Kovács, I. P., Bugya, T., Czigány, Sz, Defilippi, M., Lóczy, D., Riccardi, P., Ronczyk, L., Pasquali, P.
• Format: Article
• Language: English
• Subjects: Active control; Algorithms; Case studies; Civil Engineering; Coherent scattering; Data; Deformation; Detection; Earth; Earth and Environmental Science; Earth Sciences; Environmental Management; Geomorphology; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Hydrogeology; Image acquisition; Image detection; Imagery; Interferometry; Landslides; Line of sight; Mapping; Natural Hazards; Noise; Noise reduction; Original Paper; Photosystem I; Radar; Radar imaging; Remote sensing; SAR (radar); Satellites; Signal-to-noise ratio; Spaceborne remote sensing; Synthetic aperture radar
• ISSN: 0921-030X; 1573-0840
• DOI: 10.1007/s11069-018-3564-9

It is a crucial issue to better understand the usability of Sentinel-1 satellites in geomorphologic applications, since Sentinel-1 and the Copernicus Program are considered to be the workhorse of Earth observation by the European Space Agency during the next decades. Yet, a very limited experience is available on the applicability of Sentinel-1 images in the detection and identification of surface deformations and especially landslide mapping and monitoring in densely vegetated (low-coherence) areas. Few Synthetic Aperture Radar images (not more than 20) are sufficient for a successful run of interferometric stacking algorithms. This number is really low compared to the tremendous data flow of Sentinel-1 images that are available for interferometric analysis nowadays. Despite the availability of acquisitions, only a few papers exist on the accuracy of Sentinel-1 data, signal-to-noise ratio and the value of the acquired imagery for geomorphologic interpretation. Two test sites and a control site—affected by active surface deformations—have been investigated using 40 Sentinel-1A images and conventional persistent scatterers (PSI) method. PSI results have been combined with the geomorphologic information of the studied sites. We verified that the given number of Sentinel-1A acquisitions provide a unique base for surface deformation recognition and mapping in low-coherence areas. We found that scatterers were corrupted by a strong noise if their line of sight (LOS) velocity was below ± 6–7 mm/year all over the three test sites, although noise can easily be reduced. Noise reduction was achieved by a significant increase of the length of time series, i.e., time range between the first and last image to reduce the effect of atmospheric phase screen (APS).