Agricultural parcels serve as basic units for conducting agricultural practices and applications, which is vital for land ownership registration, food security assessment, soil erosion monitoring, etc. However, existing agriculture parcel extraction studies only focus on mid-resolution mapping or regular plain farmlands while lacking representation of complex terraced terrains due to the demands of precision agriculture. In this paper, we introduce a more fine-grained terraced parcel dataset named GTPBD (Global Terraced Parcel and Boundary Dataset), which is the first fine-grained dataset covering major worldwide terraced regions with more than 200,000 complex terraced parcels with manually annotation. GTPBD comprises 47,537 high-resolution images with three-level labels, including pixel-level boundary labels, mask labels, and parcel labels. It covers seven major geographic zones in China and transcontinental climatic regions around the world. Compared to the existing datasets, the GTPBD dataset brings considerable challenges due to the: (1) terrain diversity; (2) complex and irregular parcel objects; and (3) multiple domain styles. Our proposed GTPBD dataset is suitable for four different tasks, including semantic segmentation, edge detection, terraced parcel extraction and unsupervised domain adaptation (UDA) tasks. Accordingly, we benchmark the GTPBD dataset on eight semantic segmentation methods, four edge extraction methods, three parcel extraction methods and five UDA methods, along with a multi-dimensional evaluation framework integrating pixel-level and object-level metrics. GTPBD fills a critical gap in terraced remote sensing research, providing a basic infrastructure for fine-grained agricultural terrain analysis and cross-scenario knowledge transfer. The code and data are available at https://github.com/Z-ZW-WXQ/GTPBD/.

Reference-based super-resolution (RefSR) has the potential to build bridges across spatial and temporal resolutions of remote sensing images. However, existing RefSR methods are limited by the faithfulness of content reconstruction and the effectiveness of texture transfer in large scaling factors. Conditional diffusion models have opened up new opportunities for generating realistic high-resolution images, but effectively utilizing reference images within these models remains an area for further exploration. Furthermore, content fidelity is difficult to guarantee in areas without relevant reference information. To solve these issues, we propose a change-aware diffusion model named Ref-Diff for RefSR, using the land cover change priors to guide the denoising process explicitly. Specifically, we inject the priors into the denoising model to improve the utilization of reference information in unchanged areas and regulate the reconstruction of semantically relevant content in changed areas. With this powerful guidance, we decouple the semantics-guided denoising and reference texture-guided denoising processes to improve the model performance. Extensive experiments demonstrate the superior effectiveness and robustness of the proposed method compared with state-of-the-art RefSR methods in both quantitative and qualitative evaluations. The code and data are available at https://github.com/dongrunmin/RefDiff.

Change detection in remote sensing is crucial for land use/land cover (LULC) change awareness. However, large-scale change detection suffers from limited contextual understanding of spatial intricacies of large changes in existing CNN-based methods. Overlapped receptive fields lead to weight sharing across feature sliders, contributing to limited detection ability on large dense multi-class changes. To address this problem, this paper presents a receptive convolution operation for large-scale multi-class change detection from high-resolution remote sensing images. Different from existing CNN-based networks, our architecture involves receptive convolutions with a large kernel size to guarantee focus on different receptive field features. Experiments on SECOND datasets show that the proposed method achieves better performance than previous counterparts. Furthermore, a large-scale LULC change detection is conducted to demonstrate the ability in large-scale applications.

Efficient and timely assessment of road network dynamic changes is crucial for the comprehensive evaluation of urban development, transportation accessibility, and environmental impacts. While existing methods mainly focus on optimizing performance with very-high-resolution remote sensing images on public road datasets, their practical applicability remains to unlock when confronted with large-scale real-world applications utilizing multi-spectral remote sensing images. The limitations manifest in unsatisfactory model generalization and fragmented segmentation, reducing the effectiveness of road extraction outcomes. To address these challenges, this study introduces a novel connectivity-aware approach tailored to address road extraction challenges in real-world scenarios. Leveraging Sentinel-2 multi-spectral imagery, this study conducts a 6-year road change mapping over an expansive 10,097 square kilometers in Xi’an, China. Experimental and evaluation results underscore the efficacy of the proposed methodology for widespread applications in urban planning and environmental management, offering a robust solution for practical and efficient road extraction in diverse and extensive large-scale urban investigation.

Fine urban change segmentation using multi-temporal remote sensing images is essential for understanding human-environment interactions in urban areas. Although there have been advances in high-quality land cover datasets that reveal the physical features of urban landscapes, the lack of fine-grained land use datasets hinders a deeper understanding of how human activities are distributed across landscapes and the impact of these activities on the environment, thus constraining proper technique development. To address this, we introduce FUSU, the first fine-grained land use change segmentation dataset for Fine-grained Urban Semantic Understanding. FUSU features the most detailed land use classification system to date, with 17 classes and 30 billion pixels of annotations. It includes bi-temporal high-resolution satellite images with 0.2-0.5 m ground sample distance and monthly optical and radar satellite time series, covering 847 km^2 across five urban areas in the southern and northern of China with different geographical features. The fine-grained land use pixel-wise annotations and high spatial-temporal resolution data provide a robust foundation for developing proper deep learning models to provide contextual insights on human activities and urbanization. To fully leverage FUSU, we propose a unified time-series architecture for both change detection and segmentation. We benchmark FUSU on various methods for several tasks. Dataset and code are available at: https://github.com/yuanshuai0914/FUSU.

In high-resolution remote sensing images (RSIs), complex composite object detection (e.g., coal-fired power plant detection and harbor detection) is challenging due to multiple discrete parts with variable layouts leading to complex weak inter-relationship and blurred boundaries, instead of a clearly defined single object. To address this issue, this article proposes an end-to-end framework, i.e., relational part-aware network (REPAN), to explore the semantic correlation and extract discriminative features among multiple parts. Specifically, we first design a part region proposal network (P-RPN) to locate discriminative yet subtle regions. With butterfly units (BFUs) embedded, feature-scale confusion problems stemming from aliasing effects can be largely alleviated. Second, a feature relation Transformer (FRT) plumbs the depths of the spatial relationships by part-and-global joint learning, exploring correlations between various parts to enhance significant part representation. Finally, a contextual detector (CD) classifies and detects parts and the whole composite object through multirelation-aware features, where part information guides to locate the whole object. We collect three remote sensing object detection datasets with four categories to evaluate our method. Consistently surpassing the performance of state-of-the-art methods, the results of extensive experiments underscore the effectiveness and superiority of our proposed method.

Semi-supervised learning has attracted increasing attention in the large-scale land cover mapping task. However, existing methods overlook the potential to alleviate the class imbalance problem by selecting a suitable set of unlabeled data. Besides, in class-imbalanced scenarios, existing pseudo-labeling methods mostly only pick confident samples, failing to exploit the hard samples during training. To tackle these issues, we propose a unified Class-Aware Semi-Supervised Semantic Segmentation framework. The proposed framework consists of three key components. To construct a better semi-supervised learning dataset, we propose a class-aware unlabeled data selection method that is more balanced towards the minority classes. Based on the built dataset with improved class balance, we propose a Class-Balanced Cross Entropy loss, jointly considering the annotation bias and the class bias to re-weight the loss in both sample and class levels to alleviate the class imbalance problem. Moreover, we propose the Class Center Contrast method to jointly utilize the labeled and unlabeled data. Specifically, we decompose the feature embedding space using the ground truth and pseudo-labels, and employ the embedding centers for hard and easy samples of each class per image in the contrast loss to exploit the hard samples during training. Compared with state-of-the-art class-balanced pseudo-labeling methods, the proposed method improves the mean accuracy and mIoU by 4.28% and 1.70%, respectively, on the large-scale Sentinel-2 dataset with 24 land cover classes.

Object detection in remote sensing imagery builds the essential foundation of aerial and satellite image understanding, being an important role in many common real-world tasks and attracting world-wide attention. In recent years, despite the great progress of common object detection in remote sensing and the proven success of deep learning in this field, yet complex object detection which consists of multiple objects with variable layouts in remote sensing (e.g., coal-fired power plant, airport, sewage treatment plant, etc.) is still challenging for complex composite spatial relationship, non-rigid boundaries, and complicated surrounding textures. These challenges necessitate developing specific complex object detection methods to learn inter-relationship and distinctive and discriminative features in complex objects. To address this problem, in this paper, we propose a method, i.e., CO-Detector, in an end-to-end manner, to achieve various complex composite object detection in remote sensing images with high accuracy and efficiency. The effectiveness of CO-Detector is built on three main parts: (a) First, as surrounding contexts are normally complicated and similar to complex objects, we propose a Tandem Attention Network (TAN), including a channel enhanced network and a spatial enhanced network, with a K-global max/average pooling, to restrain noise disturbance and highlight complex object features and boundaries. (b) Second, we design a Part Region Proposal Network (P-RPN) to learn the interrelationship between parts in one object, generating part proposals and locating discriminative and distinctive object parts finely. (c) Third, to detect the whole complex object as well as the parts, we propose a Part Detection Network (PDN) to detect the individual parts, and detect the whole object through multi-level fused features. We train our CO-Detector model with three selected categories (i.e., coal-fired power plant, airport, oil storage tank) in three datasets, and conduct comparative experiments to evaluate and verify the performance. The comprehensive experiment results show that our CO-Detector achieves a mAP of 80.23%, outperforming 4.17%-17.83% against other cutting-edge deep learning-based detection methods. The experiment results indicate our CO-Detector has promising performance and potential in various complex object detection in highresolution remote sensing images, pending to be utilized in real large-scale applications.

Land Cover Mapping (LCM) is an important task to detect and understand the change of the earth surface. However, most LCM methods adopt supervised classifiers, and suffer from a lack of labels at a large scale. In this paper, we propose Fast-LCM, a scalable and weakly-supervised LCM method on a new Sunway supercomputer to achieve large-scale land cover mapping, requiring no manual annotations. Fast-LCM includes two major parts: (1) a distance-guided k-means module that combines textural, spectral, and temporal features, and (2) an automatic voting-based merging strategy to give each cluster a real meaning of classification system. Through careful parallelization, our Fast-LCM method scales to over 38 million cores, and provides a sustained performance for the task of China LCM. We produce a 10m resolution land cover map of China within only 3 minutes, including 1.2 minutes for IO and only 55 seconds to finish the computation. Fast-LCM achieves an accuracy of 68.85% (25-class), with 3.64% to 7.05% higher than best existing products.

Commonly recognized as an important symbol of the tropics and global warming, the glacier loss on Mt. Kilimanjaro has received worldwide attention for decades. In this paper, we propose a high-resolution glacier-cover (GC) record of Mt. Kilimanjaro over the period from 1984 to 2020, using a novel deep learning-based semantic segmentation method and Google Earth images, as well as digital elevation model (DEM) and ERA5-Land (ERA5) for snowline and temperature variations analysis. Our method achieves an accuracy of 94.37%, which proves the model's capability to record the GC areas precisely. The results show that (1) the GC area dramatically decreases from 19.2 km2to 3.6 km2during 37 years, which decreases about 4% and 2% per year from 1984 to 2000 and from 2000 to 2020 respectively, (2) the snowline altitude rises from$4,651 m$to$5,088 m$by about$437 m$, and (3) the average$5,000 m$air temperature on Mt. Kilimanjaro increases from −2.1 °C to −1.1 °C by about 1 °C. This study indicates that there will be no GC within a few decades if the current loss continues.

Automatic and accurate extraction of buildings from remote sensing images plays a vital role in many applications. However, existing approaches for building extraction generally apply high-resolution remote sensing images as input to attain high-resolution extraction results, which is time consuming and limited due to its spatiotemporal accessibility and cost. To address this challenge, in this paper, we propose an end-to-end approach, i.e., SRBuildingSeg-E2, to achieve higher-resolution building extraction from relatively low resolution remote sensing images. By integrating super resolution and semantic segmentation techniques, our proposed approach can attain high-resolution representations using low-resolution input. The quantitative assessment results reveal its promising performance in higher-resolution building extraction.

Counting and detecting oil palm trees from high-resolution remotely sensed images is a significant work for improving economy of several countries such as Malaysia, Indonesia, etc. However, rare attention have been paid on accelerating tree crown detection algorithms on high performance platforms. In this paper, we design a parallel approach for oil palm tree detection on a SW26010 many-core processor, which is used in a world-leading supercomputer, Sunway TaihuLight. Our parallel framework contains three steps, local maximum filtering, oil palm tree crown center reassignment and oil palm tree crown center merging. Experimental results indicates that our parallel approach of oil palm tree detection obtains the speedup of 32.30 times and 1.74 times for a QuickBird image with a size of$12,188\times 12,576$pixels compared with the well-optimized software implementation of the original algorithm on an Intel 12-core CPU and FPGAs.

Providing accurate and timely oil palm information on a large scale is essential for both economic development and ecological significance. However, owing to different sensors, photograph acquisition conditions, and environmental heterogeneity, the large volume and the variety of the data make it extremely challenging for large-scale and cross-regional oil palm tree detection. It is computationally expensive to train a model from images covering large heterogeneous regions and all environmental conditions for continuously accumulated multisource remote sensing data. In this letter, we propose a new multisource domain generalization (DG) method, Maximum Mean Discrepancy Deep Reconstruction Classification Network (MMD-DRCN). It learns representations from multiple source domains and obtains inspiring performance in an unknown and “unseen” target domain. Besides classification loss, our MMD-DRCN distills more representative features through reconstruction loss and aligns multisource latent features by MMD loss, both of which effectively enhance the capacity of generalization. MMD-DRCN achieves an average F1-score of 82.70% in all transfer tasks, attaining a 5.83% gain compared to Baseline (a straightforward convolutional neural network (CNN) model). Experimental results demonstrate DG poses a promising potential for large-scale and cross-regional oil palm tree detection without any information of the target domain.

Over the past decade, domain adaptation (DA) algorithms have been proposed to address domain gap problems as they do not need any interpretation in the target domain. However, most existing efforts focus on scenarios with only one source domain and one target domain. In this article, we explore the scenario with one source domain and mixed multiple target domains for remote sensing applications and propose a new algorithm, named the two-stage adaptation network (TSAN). First, we utilize the adversarial learning approach to confuse the classifier to discriminate between the source domain and the whole mixed-multiple-target domain. Second, we adopt self-supervised learning to divide the mixed-multiple-target domain with automated generation of “pseudo”-domain labels, which guides our network to learn intrinsic features of multiple target domains. Finally, these two steps are combined as an iterative procedure. We integrate a test dataset that includes five remote sensing datasets and ten classes. Our method achieves an average accuracy of 63.25% and 73.68% with two typical backbones, considerably outperforming other DA methods with an average accuracy improvement of 4.84%–20.19% and 9.06%–17.04%, respectively. Furthermore, we identify the negative transfer effect in existing mainstream DA methods in remote sensing image classification with multiple different domains.

Although deep learning has been successfully applied in the field of remote sensing image classification, it still requires time-consuming and costly annotations. In recent years, domain adaptation has been witnessed to address this problem as they do not need any human interpreted in the target domain dataset. However, most of the existing works dedicate effort on the circumstance where there is only one source domain and only one target domain. In this paper, we firstly explore one source and multiple target domains issue for remote sensing application and build a challenging mixed multi-target dataset to contribute to the community. Our method constitutes three parts. Firstly, as we are blind for the multitarget domain, we adopt meta learning to divide the mixed multi-target dataset and insert sub-target domain loss as the part of the loss function. Secondly, we apply the adversarial learning to confuse the classifier to discriminate between the source domain images and the whole mixed multi-target domain images. Finally, the meta learning and the adversarial learning are dynamically iterative procedures and the labels for domain classification in mixed multi-target dataset will be updated for a particular iteration. Our method is well-performed in the four common remote sensing dataset (AID, NWPU-RESISC45, UC Merced and WHU-RS19), including five classes (agriculture, forest, river, residential and parking). Our method achieved an average accuracy of 81.59% and outperformed other domain adaptation method. The experiment results indicate our method is promising for large-scale, multi-regional and multi-temporal remote sensing applications.

Oil palm is of great importance in agricultural productivity for many tropic developing countries and accordingly investigating as well as counting oil palms is a meaningful and valuable research. In this paper, we firstly apply Faster-RCNN, one of the most popular object detection algorithms, to detect tree crowns from satellite images. Although Faster-RCNN has an excellent performance in well-known datasets of general object detection, it does not have obvious advantages in oil palm tree detection in this study compared with other classical machine learning based methods. We argue two reasons accounting for the drawbacks of Faster-RCNN: (1) the size of each oil palm tree is too small (only 17 × 17 pixels on average) in 0.6m-resolution QuickBird satellite images; (2) there are lots of other similar trees around the oil palm trees that make it difficult to detect them correctly. In order to reach a satisfying accuracy, we tailored the Region Proposal Network (RPN) and proposed a simple but practical post-processing strategy based on empirical planting rules, filtering out the wrongly detected trees (False Positives) effectively. Eventually we achieved a higher average F1-score of 94.99% (using IOU based evaluation matrices) in our six study regions compared wtih state-of-the-art oil palm detection methods. In addition, we proposed a workflow of large-scale oil palm tree detection using high-resolution remotely sensed images based deep learning methods.

For pursuing the high speed information transmission, the design and research of the high speed SerDes circuit are actively developing now. Due to the requirements for long transmission path, intensive equalization and high speed transmission circuit testing function, two high speed SerDes circuits are designed and fabricated based on 130nm SiGe BiCMOS technology. One is for the research of the equalization techniques in ultra-high data rate so an ultra-high speed repeater is designed, and it can work at up to 50Gb/s and compensate for more than 50dB channel loss, with a power consumption of 676.5mW at 3.3V. The other is a low power pseudo-random binary sequence generator chip which can output 2×50Gb/s data, and the power consumption is 270mW at 1.8V.