Synthetic Aperture Radar (SAR) polarimetric datasets are widely used in the detection and classification of urban areas. Most methods used today are based on the decomposition of fully polarimetric SAR data, which allows for the extraction of physical information about the nature of the medium and the application of proper classification methods. According to the theory, the main and predominant backscattering mechanism for buildings is double bounce. However, when analyzing urban environments, the observed predominant backscatter may differ from theory depending on many aspects. In this paper, we analyze fully polarimetric ALOS PALSAR data for various cities located on different continents, proving that the theory does not hold for most cases. There are many factors that have an impact on the detected backscatter mechanism, and the theoretical principle of predominant double bounce in urban areas can be met only under specific conditions. These factors are, among others, the orientation of the buildings, the dimensions of the streets, the type of construction (i.e., numerous planes on the roof), etc. This paper also mentions the canonical example of San Francisco, widely analyzed in the literature, as a case showing the impact of building deorientation on double bounce scattering. This area of interest is also discussed in terms of the impact of SAR data resolution on the detection of specific backscatter mechanisms. The findings of this work are very useful for increasing the awareness of the utilization of classification approaches where only pixels with double bounce backscatter mechanisms are classified as urban areas. Moreover, the article lists factors that should be taken into consideration when performing urban area detection based only on polarimetric data and standard algorithms, such as street and building orientation, building heights, and structures.

中文翻译：

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SAR极化特征对城市二次弹跳检测的影响。

合成孔径雷达（SAR）极化数据集被广泛用于城市区域的检测和分类。今天使用的大多数方法都是基于完全极化SAR数据的分解，这可以提取有关介质性质的物理信息，并应用适当的分类方法。根据该理论，建筑物的主要反向散射机制是双重反射。但是，在分析城市环境时，根据许多方面，观察到的主要反向散射可能与理论不同。在本文中，我们分析了位于不同大陆的不同城市的全极化ALOS PALSAR数据，证明了该理论在大多数情况下不成立。有许多因素会影响检测到的反向散射机制，只有在特定条件下才能满足城市中双弹跳为主的理论原理。这些因素包括建筑物的方向，街道的尺寸，建筑类型（即屋顶上的许多平面）等。本文还提到了旧金山的典型示例，该示例在旧金山进行了广泛分析。文献中，举例说明了建筑失取向对双反射散射的影响。还根据SAR数据分辨率对特定反向散射机制检测的影响来讨论此领域。这项工作的发现对于提高人们对利用分类方法的认识非常有用，在分类方法中，只有具有双反射反向散射机制的像素被归类为城市区域。此外，