Department of Geodesy and Geoinformation, TU Wien, 1040 Vienna, Austria.
Earth Observation Data Centre for Water Resources Monitoring (EODC), 1030 Vienna, Austria.
Sensors (Basel). 2023 Jul 1;23(13):6072. doi: 10.3390/s23136072.
Radiometric Terrain Corrected (RTC) gamma nought backscatter, which was introduced around a decade ago, has evolved into the standard for analysis-ready Synthetic Aperture Radar (SAR) data. While working with RTC backscatter data is particularly advantageous over undulated terrain, it requires substantial computing resources given that the terrain flattening is more computationally demanding than simple orthorectification. The extra computation may become problematic when working with large SAR datasets such as the one provided by the Sentinel-1 mission. In this study, we examine existing Sentinel-1 RTC pre-processing workflows and assess ways to reduce processing and storage overheads by considering the satellite's high orbital stability. By propagating Sentinel-1's orbital deviations through the complete pre-processing chain, we show that the local contributing area and the shadow mask can be assumed to be static for each relative orbit. Providing them as a combined external static layer to the pre-processing workflow, and streamlining the transformations between ground and orbit geometry, reduces the overall processing times by half. We conducted our experiments with our in-house developed toolbox named , which allowed us to analyse various aspects of RTC, specifically run time performance, oversampling, and radiometric quality. Compared to the Sentinel Application Platform (SNAP) this implementation allowed speeding up processing by factors of 10-50. The findings of this study are not just relevant for Sentinel-1 but for all SAR missions with high spatio-temporal coverage and orbital stability.
辐射地形校正（RTC）零伽马后向散射大约在十年前引入，已成为分析就绪的合成孔径雷达（SAR）数据的标准。虽然与 RTC 后向散射数据一起使用对于起伏地形特别有利，但由于地形平滑比简单的正射校正要求更高的计算资源，因此需要大量的计算资源。当处理大型 SAR 数据集（如 Sentinel-1 任务提供的数据集）时，额外的计算可能会成为问题。在本研究中，我们检查了现有的 Sentinel-1 RTC 预处理工作流程，并评估了通过考虑卫星高轨道稳定性来降低处理和存储开销的方法。通过将 Sentinel-1 的轨道偏差传播到完整的预处理链中，我们表明对于每个相对轨道，局部贡献区域和阴影掩模可以被视为静态的。将它们作为组合的外部静态层提供给预处理工作流程，并简化地面和轨道几何之间的变换，可以将总处理时间缩短一半。我们使用我们内部开发的名为的工具包进行了实验，该工具包允许我们分析 RTC 的各个方面，特别是运行时性能、过采样和辐射质量。与 Sentinel 应用平台（SNAP）相比，这种实现可以将处理速度提高 10-50 倍。这项研究的结果不仅与 Sentinel-1 相关，而且与所有具有高时空覆盖范围和轨道稳定性的 SAR 任务相关。
