SDGSAT-1卫星微光影像的夜间渔船识别

现代渔民常利用鱼类的趋光特性来捕鱼,在夜晚出海时在船身安装集鱼灯,使用强烈的灯光照明来吸引鱼群,从而可以捕获大量的鱼类。开启集鱼灯的渔船在夜间微光影像上具有明显的灯光辐射特征和几何特征。可持续发展科学卫星1号(The Sustainable Development Science Satellite 1,SDGSAT-1)的微光成像仪具有10 m的空间分辨率,可以轻易地探测到夜间开启集鱼灯的渔船。使用传统的形态学方法可以检测到夜间渔船的灯光。使用SDGSAT-1卫星的微光遥感影像数据,进行夜间渔船的动态监测。分析了渔船夜间灯光在影像上的辐射特征和几何特征,构建不同渔船大小和船只种类的船只识别模型。结合自动识别系统(Automatic Identification System,AIS)数据对识别的船只目标进行匹配验证,实现了影像灯光与船只的匹配。对中国南部的某渔场开展研究。实验使用了2022年3—9月的34景微光影像及对应AIS数据,研究区域的影像覆盖率达到100%。基于船只识别技术,对不同灯组数量的渔船、货船等船只实现了检测与匹配。在禁渔期的影像中检测到疑似存在非法捕鱼的渔船灯光,为微光遥感影像服务渔业检测,以及打击禁渔期非法捕捞行为提供了有效的技术手段。

Image Distortion of Optical Coherence Tomography

A kind of image distortion in Optical Coherence Tomography (OCT) resulted from average refractive index changes between structures of bio tissue is discussed for the first time.Analysis is given on following situations:1) Exact refraction index changes between microstructures;2)The gradient of average refractive index change between different tissue layers is parallel to the probe beam;3) The gradient of average refractive index change is vertical to the probe beam.The results show that the image distortion of situation 1) is usually negligible;in situation 2) there is a spread or shrink effect without relative location error; however,in situation 3) there is a significant image error inducing relative location displacement between different structures.Preliminary design to eliminate the distortion is presented,the method of which mainly based on the image classification and pixel array re arrangement.