Takashi Shibayama

Polarimetric Scattering Properties of Landslides in Forested Areas and the Dependence on the Local Incidence Angle

This paper addresses the local incidence angle dependence of several polarimetric indices corresponding to landslides in forested areas. Landslide is deeply related to the loss of human lives and their property. Various kinds of remote sensing techniques, including aerial photography, high-resolution optical satellite imagery, LiDAR and SAR interferometry (InSAR), have been available for landslide investigations. SAR polarimetry is potentially an effective measure to investigate landslides because fully-polarimetric SAR (PolSAR) data contain more information compared to conventional single- or dual-polarization SAR data. However, research on landslide recognition utilizing polarimetric SAR (PolSAR) is quite limited. Polarimetric properties of landslides have not been examined quantitatively so far. Accordingly, we examined the polarimetric scattering properties of landslides by an assessment of how the decomposed scattering power components and the polarimetric correlation coefficient change with the local incidence angle. In the assessment, PolSAR data acquired from different directions with both spaceborne and airborne SARs were utilized. It was found that the surface scattering power and the polarimetric correlation coefficient of landslides significantly decrease with the local incidence angle, while these indices of surrounding forest do not. This fact leads to establishing a method of effective detection of landslide area by polarimetric information.

A comparison of the methods for the urban land cover change detection by high-resolution SAR data

The land cover change detection method using the standard deviation of the backscattering coefficient was suggested. Comparing with the previous method using spatial information such as correlation coefficients, it reduced the commission errors in the agricultural areas. It was found that the detection accuracy increased when the target area was large, but each changed target was difficult to detect for crowded and complex urban areas, even though high-spatial resolution airborne SAR data was used.

A landslide detection based on the change of scattering power components between multi-temporal polsar data

There is currently a great deal of interest in the use of radar polarimetry for disaster monitoring. In this context, this paper presents a result of numerical assessment of landslide detection methodology based upon the change of scattering power between multi-temporal fully polarimetric synthetic aperture radar (POLSAR) data. There are several types of natural disaster. Among them, we tried to detect sediment disaster including landslide, slope failure, debris flow, from POLSAR data. Sediment disasters are those that occur on mountain slopes. Mountain slopes in warm and humid regions such as Japan are usually covered by vegetation. Sediment disasters are triggered by heavy rainfall or an earthquake. Soil and vegetation flow down the slopes. Therefore the original slope changes to a slope with bare soil. The scattering process of the microwave comes to the surface scattering from the volume scattering. Therefore, we select a mountainous area stricken by a large earthquake. The four-component scattering model decomposition was applied to the POLSAR data over the area. The data acquisitions were conducted before and after the earthquake. Compared sediment disasters interpreted from aerial photographs with the scattering power decomposition images; it is revealed that the surface scattering increased after the event as compared to the volume scattering as expected.

Recent experiences utilizing TerraSAR-X for the monitoring of natural disasters in different parts of the world

PASCO in approximately 4 years, after the launch of TerraSAR-X (TSX), has successfully carried out a total 22 studies of disaster response for the worldwide and domestic cases. The outline and a part of the conducted cases are explained in detailed in this paper.

An application of polarimtric radar analysis on geophysical phenomena

It is known that all weather capability makes radar remote sensing the most suitable measure for natural disaster monitoring. Among them, fully polarimetric SAR (POLSAR) data with amplitude and phase information, i.e., the scattering matrix; is possible to retrieve the object information in more detail regardless of the weather. We applied polarimetric method to POLSAR data over actual disaster suffered area to show the efficiency of POLSAR data for disaster monitoring. A large scale landslide was clearly detected in a single decomposed image. Also, identifying landslides newly generated by an earthquake was possible to compare decomposed images of pre and post an earthquake. It is important that utilizing images observed in different direction (orbit) to reduce omission errors.

Validation of four-component decomposition with rotated coherency matrix of TerraSAR-X

TerraSAR-X is an operational and advanced SAR-satellite system for scientific and commercial applications that was launched on June 15th, 2007. DLR acquired the quadratic TerraSAR-X data in the Dual Receive Antenna Campaign in this year for scientific purpose. This study applies four-component decomposition with rotated coherency matrix which is a very efficient methodology for target detection and terrain classification.

An engineering research and development of compact and lightweight airborne SAR for extracting inundated area

Extant airborne SAR has a lot of advanced function such as full polarimetry, multi-bands, etc. However it possesses several problems and has not been becoming practical use commonly in Japan.

Monitoring and Validation of Inundation Areas Caused by The Great East Japan Earthquake and Tsunami 2011 With a High Resolution X-band SAR Satellite

1.はじめに 2011年3月11日14時46分,三陸沖を震源とするマグ ニチュード9.0の巨大地震が発生した。この地震による 大津波は,青森県から千葉県までの6県62市町村にお いて計561km,山手線内側の面積の約9倍の広大な範 囲を浸水させた(国土地理院,2011)。 宮城県の松島湾から福島県南相馬市の平野部では, 内陸側に最大で約6kmの範囲にまで津波が到達して おり,広範囲で湛水が継続する状況にあった(日経BP 社,2011)。 このような状況の中,被災地の復旧を迅速に進める ためには,効果的・効率的な排水対策を実施すること が急務の課題であった。 株式会社パスコでは,震災直後より昼夜問わず,雲 を透過して地表を定期的に観測することが可能な合成 開口レーダ(SAR:Synthetic Aperture Radar)衛星 「TerraSAR-X」による緊急観測及び継続観測を実施 してきた。 本稿では,様々な軌道・入射角・照射方向のSAR画 像の振幅情報・位相情報から,湛水域を抽出し,撮影 条件・解析手法による抽出精度の相違について結果を 報告する。さらに本検討により得られた新たな技術的 知見や得られた情報を有効活用するための運用上の課 題についても言及する。