The brightness reversal of submarine sand waves in "HJ-1A/B" CCd sun glitter images
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摘要: 环境与灾害监测预报小卫星星座A、B星(HJ-1A和HJ-1B, 合称HJ-1A/B)的太阳耀光遥感影像上呈现的浅海沙波地形会经常出现纹理特征的反转现象, 影响沙波地形的观测与水深反演. 本文基于太阳耀光辐射几何模型对浅海沙波地形归一化太阳耀光辐射值的仿真表明, 耀光反转现象的发生与传感器视角密切相关. 利用HJ-1B卫星太阳耀光遥感影像的参数, 计算得到的耀光反转临界角位置, 与实际影像上的沙波地形耀光反转位置基本一致. 仿真结果和实际耀光影像都表明, 在耀光反转临界角位置附近会出现模糊区域, 沙波地形特征变得不连续, 进而影响沙波空间特征与沙波迁移的正确分析. 通过仿真与实际耀光影像中地形特征信号强度分析, 认为在反转位置与最强太阳耀光位置之间的区域是进行沙波地形反演的最佳区域. 耀光反转现象对海面现象的观测分析具有重要影响, 应在利用HJ-1A/B卫星太阳耀光遥感影像进行内波、油膜、涡流和船舶尾迹等海洋现场观察时给予足够重视.
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关键词:
- HJ-1A/B卫星CCd影像 /
- 浅海沙波地形 /
- 太阳耀光反转现象 /
- 台湾浅滩
Abstract: The brightness reversal of submarine sand waves appearing in the small satellite constellation for environment and disaster monitoring and forecasting ("HJ-1A/B") CCd sun glitter images can affect the observation and depth inversion of sand wave topography. The simulations of the normalized sun glitter radiance on the submarine sand waves confirm that the reversal would happen at a specific sensor viewing angle, defined as the critical angle. The difference between the calculated critical angle position and the reversal position in the image is about 1', which is excellent in agreement. Both the simulation and actual image show that sand wave crests would be indistinct at the reversal position, which may cause problems when using these sun glitter images to analyze spatial characteristics and migration of sand waves. When using the sun glitter image to obtain the depth inversion, one should take the advantage of image properties of sand waves and choose the location in between the reversal position and the brightest position. It is also necessary to pay attention to the brightness reversal when using "HJ-1A/B" CCd images to analyze other oceanic features, such as internal waves, oil slicks, eddies, and ship wakes. -
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