Few-shot learning has garnered increasing attention in hyperspectral image classification (HSIC) due to its potential to reduce dependency on labor-intensive and costly labeled data. However, most existing methods are constrained to feature extraction using a single image patch of fixed size, and typically neglect the pivotal role of the central pixel in feature fusion, leading to inefficient information utilization. In addition, the correlations among sample features have not been fully explored, thereby weakening feature expressiveness and hindering cross-domain knowledge transfer. To address these issues, we propose a novel few-shot HSIC framework incorporating dynamic fusion and hierarchical enhancement. Specifically, we first introduce a robust feature extraction module, which effectively combines the content concentration of small patches with the noise robustness of large patches, and further captures local spatial correlations through a central-pixel-guided dynamic pooling strategy. Such patch-to-pixel dynamic fusion enables a more comprehensive and robust extraction of ground object information. Then, we develop a support-query hierarchical enhancement module that integrates intraclass self-attention and interclass cross-attention mechanisms. This process not only enhances support-level and query-level feature representation but also facilitates the learning of more informative prior knowledge from the abundantly labeled source domain. Moreover, to further increase feature discriminability, we design an intraclass consistency loss and an interclass orthogonality loss, which collaboratively encourage intraclass samples to be closer together and interclass samples to be more separable in the metric space. Experimental results on four benchmark datasets demonstrate that our method substantially improves classification accuracy and consistently outperforms competing approaches. Code is available at https://github.com/guoying918/DFHE2025.

Few-shot object detection (FSOD) enables the detection of novel-class objects in remote sensing images (RSIs) with limited labeled samples. Although convolutional neural networks (CNNs) are commonly used for this task, they suffer from two inherent constraints. First, their limited local receptive field fails to capture global context within a single image and the relational dependencies between query and support images. Second, an additional feature alignment mechanism is typically required to bridge the gap between query and support images. To address these challenges, this work introduces a novel cross-attention and multicorrelation aided transformer (CAMCFormer) FSOD framework tailored for global feature representation and multicorrelation modeling in complex and large-scale RSIs. Specifically, a long-distance cross-attention module (LDCAM) is devised to capture dependencies between distant elements across query and support images at each feature extraction layer. This module facilitates the exchange of contextual information between images, resulting in more comprehensive feature representations and eliminating the need for separate feature alignment and fusion modules. Multicorrelation aided heads (MAHs) are constructed to enhance detection performance further to model various relational aspects, i.e., channel-correlation detection head (CCDH), spatial-correlation detection head (SCDH), and cross-attention detection head (CADH). These aided heads contribute to more robust and accurate classification and localization. Comprehensive experiments have been conducted, demonstrating the superiority of the proposed framework compared to several state-of-the-art detectors, highlighting its potential as an effective solution for FSOD in remote sensing scenarios.

Spectral variability inevitably presents in hyperspectral images (HSIs), resulting in significant unmixing errors when using the conventional linear mixture model (LMM). Though several variants of LMM have been proposed to encounter such spectral variability, they cannot well model the complex characteristics of spectral variability, and the performance of these variants strongly depends on the prior knowledge of the scene. In this article, spectral variability within an image is classified into class-dependent variability and class-independent one, which can be tackled by a novel fully linear mixture model (FLMM) introducing a class-dependent multiplicative scaling term, a class-dependent additive perturbation term, and a class-independent variability term into the conventional LMM. Moreover, a spectral variability-aware cascaded autoencoder (SVACA) is designed to realize the automatic learning and representation of unmixing targets and spectral variability in different hyperspectral scenarios, which consists of a class-independent variability autoencoder and a cascaded class-dependent variability autoencoder. Such a network is able to handle different spectral variability autonomously without any scene prior by parallel inference structure. Experimental results over synthetic and real hyperspectral datasets demonstrate that the proposed SVACA network not only outperforms several state-of-the-art unmixing networks but also presents a stronger capability to handle spectral variability within HSIs.

Few-shot object detection (FSOD) on remote sensing images (RSIs) has garnered significant research interest due to its ability to detect novel classes using very few training examples from challenging remote sensing scenarios. Meta-learning FSOD methods, based on Faster R-CNN and YOLO structures, utilize a two-branch Siamese network as the backbone and compute the similarity between image regions for effective detection. However, almost all methods rely on extracting features using convolutional neural networks (CNNs). Inspired by the improved performance of transformer backbones for downstream tasks, a transformer-based FSOD method is proposed, which employs a transformer backbone with asymmetric-batched cross-attention for the two-branch feature extraction. Our model can improve the classification performance by introducing a Multi-Relation Matching (MRM) head for FSOD to enhance the similarity relation matching learning between two branches. Comprehensive experiments on DIOR benchmarks demonstrate the effectiveness of our model.

Recently, few-shot learning based on meta-learning has shown great potential in hyperspectral image classification (HSIC) due to its excellent adaptability to limited training samples. Despite achieving promising results, the existing methods ignore the interaction between the source domain (with abundant-labeled base-class samples) and the target domain (with few-labeled novel-class samples), as well as between the support set and the query set. This issue makes the resulting model usually biased toward the source domain and not robust to the sample variance of novel classes, posing a bottleneck to the improvement of HSIC performance. To overcome these limitations, we propose a flexible and effective distribution-aware and class-adaptive aggregation (DA-CAA) method for few-shot HSIC by transferring the class-level distribution information learned from the base classes to the novel classes. Specifically, we first employ a variational autoencoder (VAE), which is pretrained on abundant-labeled base-class samples, to encode the support set samples as class distributions. Subsequently, we sample class-level features from the learned distribution and adaptively aggregate them with sample-specific query features. This operation not only enhances cross-domain information interaction in a distribution-learning manner, but also ensures that the aggregated features across classes inherit both class-level and sample-specific information. Our proposed class-adaptive aggregation (CAA) encourages complementary fusion of features from all classes, which is beneficial for reducing class confusion. Experiments on four benchmark datasets demonstrate the effectiveness and flexibility of our approach.

Aerial person detection (APD) is vital for enhancing search and rescue (SaR) operations, particularly when locating victims in remote, poorly-lit areas. Despite advancements in detection technologies, achieving a balance between detection speed and accuracy on mobile devices in “edge AI” continues to pose challenges. In this article, a lightweight distillation network (APDNet) is proposed for edge deployment of APD, which enables real-time inference as well as minimizes accuracy loss during model transfer. The proposed APDNet employs a distillation network between varying-depth backbones and integrates an 8-bit quantized optimizer to reduce the floating-point operations of network parameters. Specifically, in the teach-assistant distillation (TAD) stage, small student models using random weight initialization are trained with pseudo-labels generated by deeper teacher models, facilitating consistent learning for a more accurate, lighter model. Moreover, a low-precision quantization (LPQ) stage incorporates an offline, quantization-aware training strategy that dynamically adjusts the ranges of weight and activation function float-point values, reducing computational complexity. In order to compensate for the potential accuracy decline, a pluggable tracker updates the position and feature information of persons frame-by-frame, with tracking results integrated with detection outputs to enhance accuracy. Extensive experiments on the Heridal, Manipal-UAV, and VTSaR datasets confirm the effectiveness of APDNet, demonstrating its superior performance in edge-based APD.

The training of deep networks for hyperspectral target detection (HTD) is usually confronted with the problem of limited samples and in extreme cases, there might be only one target sample available. To address this challenge, we propose a novel approach with dual networks in this letter. First, a training set that is not fully accurate but representative enough regarding both targets and backgrounds is built through predetection and clustering. Then, two types of neural networks, that is, one generative adversarial network (GAN) and one convolutional neural network (CNN), which focus on spectral and spatial features of hyperspectral images (HSIs), are utilized for target detection. After that, the results of the two networks are fused, with the final detection result obtained. Experiments on real HSIs indicate that the proposed approach manages to perform HTD with only one target sample and is able to yield a more robust detection performance compared to other approaches.

Spectral super-resolution (SR), which reconstructs high spatial-resolution hyperspectral images (HSIs) from RGB inputs, has been demonstrated to be one of the effective computational imaging techniques to acquire HSIs. Though deep neural networks have shown their superiority in such a complex mapping problem, existing networks generally involve a very complex structure with huge amounts of parameters, resulting in giant memory occupation. In this article, a lightweight multiresolution feature fusion network (MRFN) is proposed, which adopts a multiresolution feature extraction and fusion framework to fully explore RGB inputs in different scales of resolution. Specifically, a lightweight feature extraction module (LFEM), which adopts cheap convolution and attention mechanisms, is constructed to explore different scales of features under a lightweight structure. Moreover, a hybrid loss function is proposed by encountering not only pixel-value level reconstruction error but also spectral continuity and fidelity. Experiments over three benchmark datasets, i.e., CAVE, Interdisciplinary Computational Vision Laboratory (ICVL), and NTIRE2022 datasets, have demonstrated that the proposed MRFN can reconstruct HSIs from RGB inputs in higher quality with fewer parameters and computational floating-point operations (FLOPs) compared with several state-of-the-art networks.

Most object detection methods based on deep learning require large amounts of labeled data and can detect only the categories in the training set. Such issues significantly limit applications in remote sensing scenarios where it usually needs to recognize novel, unseen objects given very few training examples. To address these limitations, a novel meta-learning-based object detection method using Faster R-CNN framework is proposed for optical remote sensing image. Specifically, a diversity measurement module is proposed to measure diversity information between support images and query images on base classes so as to acquire more meta-knowledge. Experiments on DIOR dataset demonstrate our method has achieved superior performance than state-of-the-art meta-learning detection models in the field of remote sensing.

Collaborative representation (CR) has been demonstrated to be very effective for hyperspectral image classification. However, insufficient diversity of training samples often results in limited classification accuracy under small-training-sample conditions, especially when diverse spectral variation is presented in testing samples. In order to alleviate such a problem, a spectral variation augmented-based linear mixed model (SV-LMM) is proposed, in which the spectral variation is extracted by conducting singular value decomposition (SVD) over training samples. Such spectral variation is further utilized to extend the CR for hyperspectral classification. Experiments over two benchmark datasets, i.e., the Pavia Center dataset and the University of Houston dataset, demonstrate that the proposed extended CR-based classifier (ECRC) clearly improves the performance of conventional CRC for hyperspectral classification and outperforms several state-of-the-art algorithms.

Deep learning-based methods have drawn great attention in hyperspectral unmixing and obtained promising performance due to their powerful learning capability. However, few existing networks explicitly deal with the spectral variability inevitably present in hyperspectral images, limiting their fitting performance. In this letter, a spectral variability augmented two-stream network (SVATN) is designed to explicitly address the problem of spectral variability in a deep convolutional network for sparse unmixing. Specifically, the proposed SVATN maps a random input to coefficients of spectral variability in addition to abundances of endmembers, in which spectral variability is accommodated by the linear mixture model as an augmented item. Moreover, a spatial-spectral correlation-based variability extraction method (SSCVE) is proposed to construct a spectral variability library, which serves as priors in the loss function to optimize the proposed SVATN. Experiments over synthetic and real data sets demonstrate the superiority of the proposed SVATN over several state-of-the-art methods. The code of our proposed method is released at: https://github.com/MeiShaohui/SVATN.

Due to variation of imaging conditions, spectra of the same type of ground objects usually exhibit certain discrepancy, leading to intra-class spectral distance increase and inter-class distance decrease. As a result, classification accuracy is greatly affected, especially in cases with few labeled samples. For representation based classifiers, the spectral variability within limited training samples is far from sufficient to represent diverse variations within testing ones. To handle this problem, a spectral variation augmented representation for hyperspectral imagery classification (SVARC) with few labeled samples is proposed in this article. Firstly, a novel class-independent and class-dependent components based linear representation model (CICD-LRM) is proposed to emphasize the representation of spectral variation. Secondly, depending on spatial and spectral correlation, the CICD-LRM guided global and local spectral variation extraction schemes are designed, and a fused spectral variation dictionary is constructed by concatenation. Finally, a classifier for hyperspectral images based on the CICD-LRM and spectral variation dictionary is proposed, and specifically three different spectral variation reconstruction strategies are designed. Similar to most of the representation based classifiers, residual-driven decision is also employed in the proposed classifier. Comparative experiments are conducted with eight classical and state-of-the-art methods using two benchmark datasets. The experimental results demonstrate that the proposed SVARC method significantly outperforms the compared ones in cases with few labeled samples.

Spectral unmixing expresses the mixed pixels existing in hyperspectral images as the product of endmembers and their corresponding fractional abundances, which has been widely used in hyperspectral imagery analysis. However, the endmember spectra even for pixels from the same material of an image may include variability due to the influence of lighting conditions and inherent properties of materials within different pixels. Though thein situspectral library has been used to accommodate such variability by using multiplein situspectra to represent each kind of material, the performance improvement may be restricted due to the limited number of endmembers for each material. Therefore, in this article, spectral variability is directly extracted from anin situendmember library and considered to be transferable among different endmembers for the first time. Furthermore, such a spectral variability is further used to augment sparse unmixing by synchronously performing endmember-based reconstruction and spectral variability-augmented reconstruction in the sparse unmixing model. By, respectively, imposing sparse and smoothness regularization over abundances and variability coefficients, a convex optimization-based spectral variability augmented sparse unmixing (SVASU) is finally proposed, and its convergence performance is also analyzed. Experiments conducted over synthetic and real-world datasets demonstrate that the proposed SVASU method not only significantly improves the unmixing performance of conventional spectral library-based unmixing but also outperforms several state-of-the-art sparse unmixing algorithms.

Hyperspectral remote sensing images are well-known for their abundant spectral characteristics to discriminate different object materials. However, due to the constraints of sensor limitations and exceedingly high acquisition costs, it is difficult to obtain high spatial resolution hyperspectral imagery. Though many methods have been focusing on the restoration of the spatial structure information, spectral information may be over-smoothed during such spatial super-resolution. In this paper, a novel self-calibrated attention residual network (SCARN) is proposed to increase spatial resolution of hyperspectral images while retain spectral consistency. In particular, a self-calibrated attention residual block (SCARB) is elaborately designed to fully exploit the spatial information and the correlation between the spectra of the hyperspectral data. Concretely, self-calibrated convolution, instead of standard convolution, is adopted to adaptively construct long-range spatial and spectral dependencies around each spatial location of hyperspectral imagery, and attention module is inserted to improve the representation ability of spectral information. Finally, global and local residual connections are designed to ease the network training difficulty and maintain a higher restoration accuracy. Experimental results over two benchmark hyperspectral datasets demonstrate the effectiveness and superiority of the proposed SCARN method against the state-of-the-art methods.

In recent years, researchers have frequently utilized convolutional neural networks (CNNs) to classify hyperspectral images and have, indeed, embraced exciting achievements. However, most of the existing approaches tend to handle images block by block, which is less efficient as image blocks need to be fed into the network for many times. With this in mind, this letter presents a novel hierarchical CNN that adopts raw images as the input and extracts useful features for classification. Specifically, we adopt several hierarchical convolutional neural layers as a feature extractor and adopt the support vector machine instead of the classifying layer in the original network as the final classifier. Experiments show the proposed approach can work efficiently and exhibit competitive performance when compared to some other approaches based on deep networks.

Collaborative representation plays an increasingly important role in the field of hyperspectral imagery target detection, resulting in improving detection performance. It is known that, in hyperspectral imagery, both the sensor and external factors (such as weather, illumination and other environmental changes) will lead to the spectral variations within the same type of material, which may greatly affect the detection accuracy. To deal with this issue, a new target detection method using collaborative representation with spectral variation extended dictionary is proposed for hyperspectral imagery in this paper. In the proposed method, an extended dictionary is constructed by enclosing the spectral variation library into the original dictionary, and the following collaborative representation makes the atoms in both original dictionary and spectral variation library contribute to the residual estimation. Compared to the traditional collaborative representation based target detection method, the newly proposed one exhibits better detection performance.

Hyperspectral unmixing has been widely used to decompose a mixed pixel into a collection of endmembers weighted by their corresponding fractional abundances, in which endmember extraction step is of crucial importance. Many classical endmember extraction algorithms mainly identify spectrally pure endmembers according to spectra of pixels, e.g., NFINDR and vertex component analysis (VCA), ignoring spatial distribution or structure information that has been demonstrated to be complemental for spectral information in hyperspectral image processing. In order to improve the performance of these classical endmember extraction algorithms, a novel spatial preprocessing method is proposed to explore spatial information prior to endmember extraction step. Specifically, pixels in hyperspectral images are modified using their sparse linear approximation by neighboring pixels, such that spectral variation within a local spatial neighbor-hood can be alleviated. Experimental results on both simulated and real data sets demonstrate that the proposed local sparse representation based spatial preprocessing algorithm is capable of producing better unmixing result compared to several state-of-the-art spatial preprocessing methods.