In remotely sensed images, high intra-class variance and inter-class similarity are ubiquitous due to complex scenes and objects with multivariate features, making semantic segmentation a challenging task. Deep convolutional neural networks can solve this problem by modelling the context of features and improving their discriminability. However, current learning paradigms model the feature affinity in spatial dimension and channel dimension separately and then fuse them in a sequential or parallel manner, leading to suboptimal performance. In this study, we first analyze this problem practically and summarize it as attention bias that reduces the capability of network in distinguishing weak and discretely distributed objects from wide-range objects with internal connectivity, when modeled only in spatial or channel domain. To jointly model both spatial and channel affinity, we design a synergistic attention module (SAM), which allows for channel-wise affinity extraction while preserving spatial details. In addition, we propose a synergistic attention perception neural network (SAPNet) for the semantic segmentation of remote sensing images. The hierarchical-embedded synergistic attention perception module aggregates SAM-refined features and decoded features. As a result, SAPNet enriches inference clues with desired spatial and channel details. Experiments on three benchmark datasets show that SAPNet is competitive in accuracy and adaptability compared with state-of-the-art methods. The experiments also validate the hypothesis of attention bias and the efficiency of SAM.

Semantic segmentation of remote sensing images (RSIs) is vital for numerous geospatial applications, including land-use mapping, urban planning, and environmental monitoring. Traditional neural networks for semantic segmentation primarily focus on learning in the spatial domain, which often results in suboptimal performance due to the complexity of RSIs that exhibit diverse and intricate structures. To address this problem, we propose a novel frequency decoupling network (FDNet) that enhances feature representation by independently refining high-frequency and low-frequency components in the frequency domain. FDNet introduces three core components: a sparse-aware spectral enhancement module (SSEM) that optimizes spectral feature learning by compressing redundant information while highlighting informative spectral bands, a frequency decoupling attention module (FDAM) that precisely distinguishes and enhances high-frequency and low-frequency features, and an attentive frequency context module (AFCM) that integrates SSEM and FDAM into a cohesive framework for enriched spectral context modeling. Extensive experiments conducted on four benchmark datasets demonstrate that FDNet outperforms several state-of-the-art methods, achieving superior segmentation accuracy and robustness across various terrains and imaging conditions. Ablation experiments further confirm the impacts of SSEM, FDAM and AFCM.

High spatial resolution remote sensing images (HRRSIs) contain intricate details and varied spectral distributions, making their semantic segmentation a challenging task. To address this problem, it is crucial to adequately capture both local and global contexts to reduce semantic ambiguity. While self-attention modules in vision transformers capture long-range context, they tend to sacrifice local details. In this article, we propose a geometric prior-guided interactive network (GPINet), a hybrid network that refines features across encoder and decoder stages. First of all, a dual branch structure encoder with local-global interaction modules (LGIMs) is designed to fully exploit local and global contexts for feature refinement. Unlike commonly used skip connections or concatenations, the LGIMs bilaterally couple and exchange CNN features with transformer features by lossless transformation and elaborating cross-attention. Moreover, we introduce a geometric prior generation module (GPGM) that iteratively updates the randomly initialized geometric prior. Subsequently, the geometric priors are stored and used to guide feature recovery. Finally, a weighted summation is applied to the upsampled decoded features and geometric priors. By comprehensively capturing contexts and enabling lossless decoding and deterministic inference, GPINet allows the network to learn discriminative representations for accurately specifying pixel-level semantics. Experiments on three benchmark datasets demonstrate the superiority of the proposed GPINet over state-of-the-art methods. Furthermore, we validate the effectiveness of geometric priors and compare the model sizes.

Semantic segmentation of high-resolution remote sensing images remains challenging due to the degradation of high-frequency semantic cues during convolutional encoding and the lack of frequency consistency in multi-stage feature fusion. To address these issues, we propose FreDNet, a frequency-guided denoising network that explicitly enhances frequency-sensitive representations throughout the segmentation process. Specifically, we introduce the Dual-path Residual Block (DRB), which incorporates a Frequency-aware Denoising Module (FDM) and a Frequency-aware Fusion Module (FFM) to suppress frequency-domain noise while preserving edge structures. Furthermore, we design a Frequency-aware Cross-level Fusion Module (FCFM) that leverages frequency intensity response maps to adaptively fuse encoder and decoder features. These components work collaboratively to enhance the frequency robustness and spatial consistency of the segmentation predictions. Extensive experiments on three challenging benchmarks, ISPRS Vaihingen, ISPRS Potsdam, and LoveDA, demonstrate that FreDNet achieves superior performance, surpassing the latest state-of-the-art approaches by up to 0.8% in mean IoU and 0.9% in overall accuracy, while maintaining a lightweight inference cost. In addition, ablation study confirms the contribution of each component of FreDNet.

Since DCNNs (deep convolutional neural networks) have been successfully applied to various academic and industrial fields, semantic segmentation methods, based on DCNNs, are increasingly explored for remote-sensing image interpreting and information extracting. It is still highly challenging due to the presence of irregular target shapes, and similarities of inter – and intra-class objects in large-scale high-resolution satellite images. A majority of existing methods fuse the multi-scale features that always fail to provide satisfactory results. In this paper, a dual attention deep fusion semantic segmentation network of large-scale satellite remote-sensing images is proposed (DASSN_RSI). The framework consists of novel encoder-decoder architecture, and a weight-adaptive loss function based on focal loss. To refine high-level semantic and low-level spatial feature maps, the deep layer channel attention module (DLCAM) and shallow layer spatial attention module (SLSAM) are designed and appended with specific blocks. Then the DUpsampling is incorporated to fuse feature maps in a lossless way. Peculiarly, the weight-adaptive focal loss (W-AFL) is inferred and embedded successfully, alleviating the class-imbalanced issue as much as possible. The extensive experiments are conducted on Gaofen image dataset (GID) datasets (Gaofen-2 satellite images, coarse set with five categories and refined set with fifteen categories). And the results show that our approach achieves state-of-the-art performance compared to other typical variants of encoder-decoder networks in the numerical evaluation and visual inspection. Besides, the necessary ablation studies are carried out for a comprehensive evaluation.