Enhancing minority class recovery in high resolution land cover mapping with dynamic imbalance aware oversampling

Semantic segmentation in remote sensing is frequently hindered by severe class imbalance, where over-represented land-cover categories overshadow critical minority ones. Conventional mitigation techniques, including cost-sensitive loss functions and stochastic data augmentation, often fail to generate sufficient diversity or preserve the structural and contextual integrity required for high-resolution imagery. On the other hand, generative approaches may be very data demanding, or become prone to creating semantic contradictions, thereby introducing significant noise into the training signal. To address this problem, we present dynamic imbalance-aware oversampling (DIAO) and its refined variant, DIAO-CP, specifically designed to overcome these challenges in pixel-level classification, specific to semantic segmentation tasks. DIAO replaces random sampling with an iterative density-driven scoring function that identifies images to be resampled based on their potential to minimize global distribution entropy. DIAO-CP extends this logic by integrating an object-centric synthesis loop that ensures context-sensitive placement, preventing semantic collisions by utilizing a background selection filter. These mechanisms ensure that synthesized samples maintain both statistical equilibrium and geographic plausibility. The proposed methods were evaluated on relevant semantic segmentation benchmarks, specifically the Chesapeake Conservancy and OpenEarthMap (OEM). Results indicate that DIAO-CP successfully optimized the information structure of the datasets, reducing the Kullback-Leibler divergence from an initial 0.3380 to 0.1924 in the OEM benchmark. In terms of predictive performance, our solutions yielded an average improvement of 10.5 and 11.8 percentage points (p.p.), respectively, in Macro F1 and mIoU compared to baseline model without using DIAO for all regions. As such, the DIAO strategies demonstrated a superior ability to recover rare semantic entities for minority classes. These findings confirm the effectiveness of our approach in enhancing the discriminative power for imbalanced classes in diverse geographic scales within semantic segmentation workflows.