Mathematical morphology approach to detect farmland conditions from ALOS/PALSAR data after the 2011 off the pacific coast of Tohoku Japan earthquake and Tsunami

The north-eastern coast of main island of Japan, Tohoku region, was hit by the great earthquake and the big Tsunami on March 11^th, 2011. There are farm lands, mainly paddy fields, along the coast line in many places of Tohoku region. The Tsunami made those lands along the seashore a vacant lot. The grounds have been sinking in some areas after the earthquake. The ALOS/PALSAR was observed on March 13rd, March 17th of 2011 in this region. Those data are HH polarization, pixel spacing 6.25m. After the Tsunami tidal wave, the fields became flat because of soil sediment. The difference of back scattering DN value between the Tsunami inundated and not inundated areas is not big. So the boundary line is obscure by only amplitude information. The terrain feature recognition procedure of the SAR data should be improved. The improved procedure combined with adaptive threshold and morphological opening filtering shows fairly good result. This procedure required only a few minutes for each image by using an ordinary PC.