Robustness Comparison of Spatiotemporal Fusion Models With High Spatial Resolution Satellite Images

The construction of high spatial and temporal image time series through spatiotemporal image fusion is vital for environmental monitoring and time-series analysis. However, most existing spatiotemporal image fusion models were originally developed for mid- and coarse spatial resolution satellite images, limiting their applicability to high spatial resolution images. To address this limitation, it is critical to identify models that are robust across different fusion strategies when applied to high spatial resolution images. This study evaluates the robustness of three representative weight function-based models, the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM), Flexible Spatiotemporal Data Fusion (FSDAF), and Fit-FC, using PlanetScope and Sentinel-2 images from agricultural sites with varying degrees of spatial heterogeneity. The analysis focuses on three key factors related to input data characteristics that influence fusion performance: differences in image acquisition times, differences in spatial resolution ratio, and the impact of radiometric normalization. A relative robustness index (RRI), defined as the coefficient of variation of multi-band prediction results across experimental scenarios, is introduced to facilitate the quantitative comparison of model robustness. Experimental results show that model robustness depends on both landscape heterogeneity and input data characteristics. Fit-FC was the most robust among the three models, particularly in heterogeneous landscapes. These findings provide practical insights for selecting robust models for spatiotemporal fusion in real-world applications using multi-sensor high spatial resolution images.