合成開口レーダによる海岸地形情報の抽出  [in Japanese] SHORELINE POSITIONS AND BOTTOM PROFILES RETRIEVED FROM SYNTHETIC APERTURE RADAR  [in Japanese]

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Abstract

合成開口レーダ(SAR)は全天候型のリモートセンシング手法で,海岸工学分野においてもその観測データの活用が進んでいる.SARはマイクロ波を地表に向けて射出し,その後方散乱を計測するレーダである.この際に様々な観測パラメータを設定できること,対象物の散乱特性が多様であること等により,SARで取得されるシーンは,直感的に理解が可能な可視光観測のシーンに比べ,判読,解析等が難しいと指摘されることが多い.本研究ではSARが取得したシーンを分析し,汀線位置の検出精度の検証,波浪の伝播に伴う波数と水深分布の推定,観測パラメータによるシーン取得状況の分析等を行い,SARによる海岸地形情報抽出の可能性について議論する.

 Synthetic Aperture Radar (SAR) is a powerful tool in retrieving shoreline positions and surface wave patterns in the nearshore, since it can gather scenes in any weather condition. The interpretation of scenes is sometimes not straightforward due to the various parameters set in the active observation of SAR. In this study, several scenes which captured Kashimanada Coast, Japan were analyzed to infer the usability of SAR data to extract shoreline positions and wave number variations in the nearshore, and also the influence of various parameters in the observation is discussed. Shoreline positions along the 15 km long sandy beach were digitized manually from the scene, and compared with aerial laser scanning survey data. The mean accuracy of shoreline position detection was in order of 10 m, which is equivalent to the resolution of SAR observation. Local accuracy decreased at regions where local foreshore slopes were mild, which was probably affected by the water content in the surface layer of sandy beach. Wave number variations from offshore to onshore were analyzed with two dimensional Fast Fourier Transform. Refraction of waves was confirmed: increase of wave number and deflection of wave angle. Off-nadir angle in SAR observation is an important parameter in coastal observation. If this angle is set to an optimized value for land observation, backscatter from water bodies is small. On the other hand, if this is angle is set smaller, backscatter from water bodies increases and wave pattern and shoreline position are captured more clearly.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 72(2), I_1735-I_1740, 2016

    Japan Society of Civil Engineers

Codes

  • NII Article ID (NAID)
    130005282350
  • Text Lang
    JPN
  • ISSN
    1884-2399
  • NDL Article ID
    027813969
  • NDL Call No.
    YH267-236
  • Data Source
    NDL  J-STAGE 
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