Document Type : Original/Review Paper
Authors
Babol Noshirvani University of Technology
Abstract
Accurate rice mapping is crucial for food security, water management, and long-term agricultural planning. This study proposes a phenology-informed LSTM framework that integrates multi-source Sentinel-1 and Sentinel-2 time-series data for robust rice mapping. Sentinel-2 optical images and Sentinel-1 SAR images were preprocessed using cloud-pixel removal, 10-day temporal compositing, and interpolation of missing observations to generate complete and temporally consistent 18-step time series over a 180-day observation period. Three indices, including Sentinel-2-derived NDVI and LSWI and Sentinel-1-derived CR, were extracted to represent vegetation greenness, surface/vegetation moisture, and radar backscatter dynamics. To incorporate rice phenological prior knowledge, reference rice phenology curves were constructed for these indices, and a sliding-window correlation analysis was applied between each pixel-level index trajectory and the corresponding reference curve. This process generated three correlation-based temporal similarity sequences, C_NDVI, C_LSWI, and C_CR, which describe how closely each pixel follows the characteristic rice growth pattern. The raw indices, correlation-based features, and their combined representation were then evaluated as sequential inputs to an LSTM classifier. The results showed that the correlation-based feature set achieved the best performance, with an overall accuracy of 99.81%, an error rate of 0.19%, and an F1-score of 0.9950. Compared with raw time-series indices and the combined feature set, the correlation-based representation improved the discrimination of rice paddies from spectrally similar classes such as water bodies and weeds. The results demonstrate that integrating phenology-informed correlation features with LSTM-based temporal learning provides an effective framework for accurate rice mapping in fragmented and cloud-prone agricultural landscapes.
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