Comparison between the research result of mathematical morphology method applied to satellite SAR data and the other reported results for the detection of the 2011 off the Pacific coast of Tohoku Japan Earthquake and Tsunami affected farmlands

摘要

A great earthquake and following great tsunami occurred on 11th March 2011 over the wide areas of the north-east of Japan. The agricultural fields along the coast were submerged under the seawater caused by the Tsunami tidal wave for some periods. The soil in such farmland suffered from salt of sea water. As soil salinity is hindrance to the crop growth, the detection of Tsunami flooded farmland is important for agriculture. ALOS satellite data were obtained from March 13th including both optical sensor data and SAR data. And aerial photograph for photogrammetry was taken from the next day of the earthquake by Geospatial Information Authority of Japan. Many research institutes and universities performed ground survey and made Tsunami flooded extent maps in that region. But as for cloud and large areas, SAR data has advantage. Therefore the author tried detecting the Tsunami flooded extents from ALOS/PALSAR HH data. The outline procedure of the analysis is threshold method for extracting the low backscattering areas as a black and white color image, opening operation of mathematical morphology using a 3 by 3 filter size for clearing small islands, dilation operation of mathematical morphology using a 3 by 3 filter size to establish united areas in the scene. The obtained images are compared to aerial photograph and ground survey maps.