Thresholding method is a general tool for classification of a population. This method is one of the picture binarization techniques. Various thresholding methods have been proposed by many researchers. Some methods proposed by Dr. Otsu and Dr. Kittler et al or Dr. Kurita have a very simple algorithm and are very easy for data handling, and these techniques have been applied for a lot of classification analysis. These are effective methods for increasing the overall accuracy of analysis. however, there are some cases in which these methods are not appropriate for a population analysis. For example, this is a case of which objective of analysis is to select a threshold to estimate the total number of data (pixels) of each classified population. In particular, If there is significant difference between the total numbers or/and variances of two populations, error possibilities in classification differ excessively from each other. Consequently, estimated total number of each classified population could be very different from the actual one. In this report, authors propose a new method which could be applied to select a threshold to estimate the total number of data more precisely in the above mentioned case. And authors verify the applicability of the new method by comparing results which are obtained with existing method and the new method. Both simulated sample data and actual satellite's data are utilized in the analysis.
InSAR image is well-known as detecting crustal movement in wide area when hazardous events like earthquakes and volcanic activities occur. In addition to grasping such wide movement, small and regional movements like landslide can be also detected from InSAR image. On the basis of the previous study on Noto Hanto Earthquake in 2007, the authors delved into possibility of the detection and monitoring at Higashi-Naruse village in Akita prefecture using ALOS/PALSAR data in this study. Also, landslide delimitation was done by making out micro-topography map created by air-borne laser data. There are many famous landslides in this area, e.g. Yachi Landslide. Among those landslides, Ohkamizawa Landslide on the right bank of Naruse river is an active one at rates of more than 10cm/year, and this landslide movement could be observed at InSAR image. This study showed that InSAR image is very useful for detecting not only just existence of landslide movements but also time variation of extent, magnitude, uniformity of movements, and also reconfirmed the usefulness of air-borne laser data in classifying landform in micro scale.
In this letter, we propose a extraction method of high density DEM (Digital Elevation Model) in inundation area. The proposed method is performed by using iris filter. Through the experiments using 5.0m mesh DEM, we prove the effectiveness of the proposed method. Finally, we comment on the respects in which the proposed method is improved and on future prospects.
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