Robust Distribution-Shift Aware Sar-Optical data Fusion for Multi-Label Scene Classification

Out-of-distribution (OOD) detection is an emerging research topic in remote sensing where existing works focus on single sensor analysis. However, many remote sensing works use multi-modal data to benefit from different characteristics of the sensors. Data that is in-domain for one sensor may be OOD for another sensor. In this work, we address such a scenario focusing on Synthetic Aperture Radar (SAR) and optical data fusion for multi-label scene classification. Besides data distribution shifts caused by unknown classes and snow, we also consider cases where only one modality is affected. Optical images acquired with significant cloud coverage are considered as OOD, while their corresponding SAR images can be in-distribution. We propose a weighted feature propagation strategy based on the in-distribution probabilities of the single modalities. We show, that we not only improve the prediction performance on the cloudy samples but also receive a higher predictive uncertainty when both modalities are OOD.