Object detection is a fundamental part of the interpretation of remote sensing imagery. The one-stage object detector has been adopted into this field because of its high computational efficiency. However, this detector suffers from the misalignment among predefined anchor, object, and feature extracted by standard convolution kernel both in spatial and scale. It limits the further improvement of performance, especially for the long-narrow and multiscale geospatial objects. In this article, the problem is defined as the feature misalignment problem. To deal with this issue, an efficient feature aligned single-shot detector (ASSD) is proposed, which consists of two modules: a novel pseudo anchor proposal module (PAPM) and a flexible context-based feature alignment module (CFAM). The PAPM replaces the regular anchor group with the proposed core anchor and refines it to get aligned locations. It can tackle the spatial misalignment between anchors and their corresponding objects and alleviate the negative/positive imbalance problem. Then, the CFAM adaptively adjusts the sampling points of the convolution kernel and collects the context information according to the aligned core anchor. This plug-and-play module can effectively rectify the misalignment between kernel and objects and extract aligned and robust features. A series of comprehensive experiments are conducted on two large-scale public remote sensing object detection datasets. Experiment results suggest that the proposed method is effective to alleviate the misalignment problem. Compared with the baseline model, the detection accuracy is improved by 8.5% mAP and 11.0% mAP on the challenging benchmark for object detection in optical remote sensing image (DIOR) and a large-scale dataset for object detection in aerial image (DOTA) dataset, respectively. Our best-resulting model achieves the state-of-the-art performance, surpassing other one-stage detectors both on the two datasets at a high detection speed of 21 FPS.

Multi-class object detection in remote sensing imagery is an important and challenging topic in computer vision. Compared with the object detection of natural scenes, remote sensing object detection has some challenges such as scale diversity, arbitrary directions and densely packed objects. To resolve these problems, this paper presents a scale-aware rotated object detection. Firstly, we propose a novel feature fusion module, which takes full advantage of high-level semantic information and low-level high resolution feature. The new feature maps are more suitable for detecting objects with a large difference in scale. Meanwhile, we design a specific weighted loss, which contains an intersection-over-union (IoU) loss and a smooth L1 loss to further address the scale diversity. Besides, in order to detect oriented and densely packed objects more accurately, we propose a normalization strategy for the representation of rotating bounding box. Our method is evaluated on two public aerial datasets DOTA and HRSC2016, and achieves competitive performances. On DOTA, we boost the mean Average Precision (mAP) to 72.95% on oriented object detection.

In recent years, remote sensing (RS) vision foundation models such as RingMo have emerged and achieved excellent performance in various downstream tasks. However, the high demand for computing resources limits the application of these models on edge devices. It is necessary to design a more lightweight foundation model to support on-orbit RS image interpretation. Existing methods face challenges in achieving lightweight solutions while retaining generalization in RS image interpretation. This is due to the complex high and low-frequency spectral components in RS images, which make traditional single CNN or Vision Transformer methods unsuitable for the task. Therefore, this paper proposes RingMo-lite, a RS lightweight network with a CNN-Transformer hybrid framework, which effectively exploits the frequency-domain properties of RS to optimize the interpretation process on several tasks like classification, object detection, semantic segmentation, and change detection. It is combined by the Transformer module as a low-pass filter to extract global features of RS images through a dual-branch structure, and the CNN module as a stacked high-pass filter to extract fine-grained details effectively. Furthermore, a novelty-designed frequency-domain masked image modeling (FD-MIM) is employed during the pretraining stage for self-supervised learning, which combines the high-frequency and low-frequency characteristics of each image patch. This approach effectively captures the latent feature representation in RS data. As shown in Fig. 1, compared with RingMo, the proposed RingMo-lite reduces the parameters over 60% in various RS image interpretation tasks, the average accuracy drops by less than 2% in most of the scenes and achieves SOTA performance compared to models of the similar size. In addition, our work will be integrated into the MindSpore computing platform in the near future.

Building 3D reconstruction from remote sensing images has a wide range of applications in smart cities, photogrammetry and other fields. Methods for automatic 3D urban building modeling typically employ multi-view images as input to algorithms to recover point clouds and 3D models of buildings. However, such models rely heavily on multi-view images of buildings, which are time-intensive and limit the applicability and practicality of the models. To solve these issues, we focus on designing an efficient DSM estimation-driven reconstruction framework (Building3D), which aims to reconstruct 3D building models from the input single-view remote sensing image. Existing DSM estimation networks suffer from the imbalance between local features and global features, which leads to over-smooth DSM estimates at instance boundaries. To address this issue, we propose a Semantic Flow Field-guided DSM Estimation (SFFDE) network, which utilizes the proposed concept of elevation semantic flow to achieve the registration of local and global features. First, in order to make the network semantics globally aware, we propose an Elevation Semantic Globalization (ESG) module to realize the semantic globalization of instances. Further, in order to alleviate the semantic span of global features and original local features, we propose a Local-to-Global Elevation Semantic Registration (L2G-ESR) module based on elevation semantic flow. Our Building3D is rooted in the SFFDE network for building elevation prediction, synchronized with a building extraction network for building masks, and then sequentially performs point cloud reconstruction and surface reconstruction (or CityGML model reconstruction). On this basis, our Building3D can optionally generate CityGML models or surface mesh models of the buildings. Extensive experiments on ISPRS Vaihingen and DFC2019 datasets on the DSM estimation task show that our SFFDE significantly improves upon state-of-the-art and δ ₁ , δ ₂ and δ ₃ metrics of our SFFDE are improved to 0.595, 0.897 and 0.970. Furthermore, our Building3D achieves impressive results in the 3D point cloud and 3D model reconstruction process.

Deep learning-based object detectors have been widely adopted in the field of remote sensing imagery interpretation. These detectors heavily depend on the expensive large-scale labeled datasets, while the scarce remote sensing datasets limit the performance. The domain adaptive object detection can alleviate this problem. However, it struggles with the confusing feature’s alignment, damaging the domain generalization performance, especially for the remote sensing scene with sparse objects and diverse backgrounds. For that reason, a semisynthetic data generator (SDG) is proposed to automatically generate the remote sensing dataset with low cost and replace the real-world training dataset, a feature aligned domain adaptive object detector (FADA) is proposed to enhance the domain adaptation among the cross-domain remote sensing images. The FADA contains two proposed modules in addition to the base detector: an adversarial-based foreground alignment (AFA) and a prototype-based confusing feature alignment (PCFA). The AFA aligns the cross-domain foreground feature by adversarial training (AT), and it can filter the noisy background feature that is not suitable to transfer. Then, the PCFA adaptively aligns the confusing background and foreground feature, further promoting the domain adaptation performance. Comprehensive experiments validate the effectiveness of the proposed method. Compared with the baseline model trained on the semisynthetic source dataset, our FADA improves the generalized performance on the real-world target dataset a large-scale Dataset for Object deTection in Aerial images (DOTA) by 15.7% average precision (AP) and achieves state-of-the-art results.

In recent years, fully supervised object detection methods in remote sensing images with good performance have been developed. However, this approach requires a large number of instance-level annotated samples that are relatively expensive to acquire. Therefore, weakly supervised learning using only image-level annotations has attracted much attention. Most of the weakly supervised object detection methods are based on multi-instance learning methods, and their performance depends on the process of scoring the candidate region proposals during training. In this process, the use of only image-level labels for supervision usually cannot obtain optimal results due to the lack of location information of the object. To address the above problem, a dynamic sample pseudo-label generation framework is proposed to generate pseudo-labels for each proposal without additional annotations. First, we propose the pseudo-label generation algorithm (PLG) to generate the category labels of the proposal by using the localization information of the object. Specifically, we propose to use the pixel average of the object’s localization map in the proposal as the proposal category confidence and calculate the pseudo-label by comparing the proposal category confidence with the preset threshold. In addition, an effective adaptive threshold selection strategy is designed to eliminate the effect of different category shape differences in computing sample pseudo-labels. Comparative experiments on the NWPU VHR-10 dataset demonstrate that our method can significantly improve the detection performance compared to existing methods.