The structure of a cloud is three-dimensional (3-D). Nevertheless, cloud research is predominantly developed in one-dimensional (1-D) hypothesis from passive optical satellite measurements. Cloud retrieval algorithms typically do not consider the parallax displacement of clouds in multi-view images. Inversion of cloud properties based on two-dimensional (2-D) coordinates cannot solve multi-view radiation changes which are caused by macro-structure of a cloud in 3-D space. In this study, we included the 3-D structure of clouds by repositioning cloud pixels within a 3-D coordinate system utilizing the directional polarization camera (DPC) data before conducting cloud property retrieval. It is followed by identification of location of cloud in each observational view’s image plane. Observational paths of clouds are rebuilt at each observational view. Furthermore, computer graphics methods are employed to establish spatial relationship among different cloud observational paths. The radiational and geometrical information are relocated in unified 3-D sub-pixel space. Finally, 3-D cloud radiation information could be applied to retrieve cloud properties. The case results demonstrate that our method can effectively reduce mixed pixels of clouds and clear sky by 5.79% while decrease indistinguishable pixels in cloud phase classification by 2.11%. It leads to an enhancement in the classification accuracy of water clouds and ice clouds by 3.30% and 4.03%, respectively. Therefore, it is concluded that considering the impact of cloud structure before retrieval would significantly improve accuracy.

中文翻译：

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针对定向偏振相机收集的 3D 结构进行多视图云检索


云的结构是三维（3-D）的。然而，云研究主要是根据无源光学卫星测量的一维 (1-D) 假设进行的。云检索算法通常不考虑多视图图像中云的视差位移。基于二维（2-D）坐标的云属性反演无法解决云在3-D空间中的宏观结构引起的多视角辐射变化。在本研究中，我们在进行云属性检索之前，利用定向偏振相机 (DPC) 数据在 3D 坐标系内重新定位云像素，从而包含云的 3D 结构。接下来是识别每个观测视图图像平面中云的位置。在每个观测视图中重建云的观测路径。此外，采用计算机图形学方法建立不同云观测路径之间的空间关系。辐射和几何信息被重新定位在统一的 3D 子像素空间中。最后，3D 云辐射信息可用于检索云属性。实例结果表明，该方法可以有效减少云与晴空的混合像素5.79%，同时将云相分类中的不可区分像素减少2.11%。水云和冰云的分类精度分别提高了 3.30% 和 4.03%。因此，得出的结论是，在检索之前考虑云结构的影响将显着提高准确性。