解决遥感影像云遮挡问题,实现任意时间点的无云图像重建。
Asynchronous Remote Sensing Time-Series Fusion for Cloud Removal and Anytime Reconstruction

- 基于时序流匹配模型,直接融合异步获取的S1与带云S2数据
- 在长时间缺失情况下仍可降低16%-19%误差,实现精准重建
- 支持任意时间点查询,适合植被等连续监测任务
频繁云层覆盖严重限制了哨兵-2(S2)光学时序数据在地表监测中的应用。哨兵-1(S1)雷达提供全天候互补观测,但实际的S1/S2融合仍具挑战,因两者采集时间不规则且异步。许多现有方法假设输入时间对齐(或需外部最近日期匹配),通常仅恢复已观测时间点,难以应对长期缺失,也无法按需合成。本文提出AGFlow(时间对齐生成流匹配)模型,具备三项能力:(1) 时序条件内部对齐,无需预处理配对即可融合异步S1与带云S2数据;(2) 融合空间结构与时间动态的时空上下文感知去噪,而非独立像素时序处理;(3) 任意时间查询,可在监测窗口内生成任意指定时间点的无云S2帧。在RESTORE-DiT基准协议下评估,量化指标、定性对比与组件消融均验证其有效性。AGFlow显著提升完全缺失帧重建性能(MAE和RMSE较RESTORE-DiT降低16%-19%),并在持续缺失场景中保持可靠重建,同时具备良好云去除表现,为密集植被监测等下游任务提供灵活时间查询能力。
原文摘要 · Abstract (English)
Frequent cloud cover severely limits the usability of Sentinel-2 (S2) optical time series for Earth surface monitoring. Sentinel-1 (S1) SAR provides all-weather complementary observations, but practical S1/S2 fusion remains difficult because acquisitions are irregular and asynchronous. Many existing approaches assume temporally aligned inputs (or require external nearest-date matching) and typically restore only observed timestamps, limiting reconstruction under long gaps and preventing on-demand synthesis. We propose AGFlow (Time Aligned Generative Flow Matching), a spatiotemporal flow-matching model for S1/S2 cloud removal and time-series reconstruction with three capabilities: (1) timestamp-conditioned internal alignment that fuses asynchronous S1 and cloudy S2 observations without preprocessing-based pairing; (2) spatiotemporal, context-aware denoising that models spatial structure jointly with temporal dynamics (rather than independent per-pixel time series); and (3) anytime querying, enabling generation of cloud-free S2 frames at both observed and user-specified timestamps within the monitoring window. We evaluate on the RESTORE-DiT benchmark protocol with quantitative metrics, qualitative comparisons, and component ablations. AGFlow notably improves fully missing-frame reconstruction (MAE and RMSE reduce by 16-19% over RESTORE-DiT) and provides reliable reconstructions under persistent gaps, while also yielding competitive cloud removal performance and flexible temporal querying for downstream tasks such as dense vegetation monitoring.
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