Continuous Observation of Natural-Disaster-Affected Areas Using Ground-Based SAR Interferometry

Ground-based synthetic aperture radar (GB-SAR) is an effective technique for monitoring over a widespread area. Save for the fact that it is installed on the ground, the GB-SAR operates in the same way as air- and satellite-borne microwave SAR remote sensing systems. By repeated acquisition of data and application of the repeat-pass interferometry principle, this technique can detect very small changes over a scene with a typically high temporal resolution of only a few minutes. In the system used in this study, interferometer error is less than 10% and the temporal resolution is approximately five minutes. Some applications require extensive monitoring capability; for instance, in this study, the GB-SAR technique was used to monitor a post-landslide surface in order to assess slope stability and to ensure the safety of the area. Whereas no major events were observed, the technique proved capable of detecting even small changes caused by snowfalls. The technique was also used to monitor the displacement of the ground surface in a tsunami-affected area in which the stability of the ground had come into question. The results of this assessment indicated that the distribution of displacement tended to be larger in waterfront areas and seemed to correlate to tidal effects. Although both of these measurement campaigns represent preliminary research, the advantages of the GB-SAR technique have been well illustrated. In this paper, the results of these measurements are provided, and the capability and potential of the technique are discussed.