GA-Net: A geometry prior assisted neural network for road extraction

This paper presents a method for road extraction from lidar data based on support vector machine (SVM) classification. The lidar data are used exclusively to evaluate the potential in the road extraction process. First, the SVM algorithm is used to classify the lidar data into five classes: road, tree, building, grassland, and cement. Then, some misclassified pixels in the road class is removed using the road values in the normalized Digital Surface Model and Normalized Difference Distance features. In the postprocessing stage, a method based on Radon transform and Spline interpolation is employed to automatically locate and fill the gaps in the road network. The experimental results show that the proposed algorithm for gap filling works well on straight roads. The proposed road extraction algorithm is tested on three datasets. An accuracy assessment indicated 63.7%, 60.26% and 66.71% quality for three datasets. Finally, centerline of the detected roads is extracted using mathematical morphology. Road information plays an important role in many modern applications, including transportation, automatic navigation systems, traffic management, and crisis management, and enables existing geographic information system (GIS) databases to be updated more efficiently. In the past two decades, automatic road extraction has become an important topic in remote sensing, photogrammetry, and computer vision. In addition, recent advances in lidar systems and their enormous potential in automatic feature extraction motivate the development of automatic road extraction algorithms based on lidar data.

This paper deals with automatic road extraction from airborne SAR imagery. Automatic extracted road networks are often incomplete. Even sophisticated road extraction approaches that are developed for optical imagery often fail to extract a complete road network. In SAR imagery in contrary to optical imagery, roads are more affected by high backscattering context objects. These local context objects like trees, bridges, or vehicles can disturb road extraction, but they can also support it. We show that an explicit modeling of context objects, leads to improved extraction results.

Traditional pixel-based semantic segmentation methods for road extraction take each pixel as the recognition unit. Therefore, they are constrained by the restricted receptive field, in which pixels do not receive global road information. These phenomena greatly affect the accuracy of road extraction. To improve the limited receptive field, a non-local neural network is generated to let each pixel receive global information. However, its spatial complexity is enormous, and this method will lead to considerable information redundancy in road extraction. To optimize the spatial complexity, the Crisscross Network (CCNet), with a crisscross shaped attention area, is applied. The key aspect of CCNet is the Crisscross Attention (CCA) module. Compared with non-local neural networks, CCNet can let each pixel only perceive the correlation information from horizontal and vertical directions. However, when using CCNet in road extraction of remote sensing (RS) images, the directionality of its attention area is insufficient, which is restricted to the horizontal and vertical direction. Due to the recurrent mechanism, the similarity of some pixel pairs in oblique directions cannot be calculated correctly and will be intensely dilated. To address the above problems, we propose a special attention module called the Dual Crisscross Attention (DCCA) module for road extraction, which consists of the CCA module, Rotated Crisscross Attention (RCCA) module and Self-adaptive Attention Fusion (SAF) module. The DCCA module is embedded into the Dual Crisscross Network (DCNet). In the CCA module and RCCA module, the similarities of pixel pairs are represented by an energy map. In order to remove the influence from the heterogeneous part, a heterogeneous filter function (HFF) is used to filter the energy map. Then the SAF module can distribute the weights of the CCA module and RCCA module according to the actual road shape. The DCCA module output is the fusion of the CCA module and RCCA module with the help of the SAF module, which can let pixels perceive local information and eight-direction non-local information. The geometric information of roads improves the accuracy of road extraction. The experimental results show that DCNet with the DCCA module improves the road IOU by 4.66% compared to CCNet with a single CCA module and 3.47% compared to CCNet with a single RCCA module.

Automatic Road Extraction from remotely sensed images is a fundamental step in the acquisition and maintenance of geographical databases. This paper proposes an automatic road recognition algorithm based on fusion of junction and segment information. Road segments and junctions in an image are independently acquired as features of edge pairs. Then, the classification decisions of the segment and junction classifiers are fused to learn initial seeds for the extended fast marching level set method. The decisions of segment classifiers and fast marching level set method are then combined to improve road extraction. The primary contribution of our approach is its ability to learn the seed points and the stopping criterion for fast marching level set methods. Experimental results on remotely sensed image datasets demonstrate the validity of the proposed algorithm.

Historical maps are valuable sources of geospatial data for various geography-related applications, providing insightful information about historical land use, transportation infrastructure, and settlements. While transformer-based segmentation methods have been widely applied to image segmentation tasks, they have mostly focused on satellite images. There is a growing need to explore transformer-based approaches for geospatial object extraction from historical maps, given their superior performance over traditional convolutional neural network (CNN)-based architectures. In this research, we aim to automatically extract five different road types from historical maps, using a road dataset digitized from the scanned Deutsche Heereskarte 1:200,000 Türkei (DHK 200 Turkey) maps. We applied the variants of the transformer-based SegFormer model and evaluated the effects of different encoders, batch sizes, loss functions, optimizers, and augmentation techniques on road extraction performance. Our best results, with an intersection over union (IoU) of 0.5411 and an F1 score of 0.7017, were achieved using the SegFormer-B2 model, the Adam optimizer, and the focal loss function. All SegFormer-based experiments outperformed previously reported CNN-based segmentation models on the same dataset. In general, increasing the batch size and using larger SegFormer variants (from B0 to B2) resulted in improved accuracy metrics. Additionally, the choice of augmentation techniques significantly influenced the outcomes. Our results demonstrate that SegFormer models substantially enhance true positive predictions and resulted in higher precision metric values. These findings suggest that the output weights could be directly applied to transfer learning for similar historical maps and the inference of additional DHK maps, while offering a promising architecture for future road extraction studies.

Scene classification is an important tool for remote sensing image interpretation, and it has fundamental applications in research and industry. However, given complex backgrounds and scale variations, remote sensing images have large intraclass diversity and interclass similarity, which bring challenges to accurate classification of remote sensing images. We proposed a scene classification method using joint learning and multiscale attention to alleviate the aforementioned problems. To fully utilize the multiscale information of the image and improve the adaptability of the proposed method to objects with various sizes, different from general methods that fuse different scales of features for classification, joint learning using multiscale features is developed to optimize the whole network. Specifically, we leverage a pretrained deep convolutional neural network as the feature extractor to extract low-level, medium-level, and high-level feature maps from the images. Then, due to the poor semantics of low-level and medium-level feature maps compared with the high-level feature maps, we design a multiscale attention module to enhance the semantic information and suppress the noise information. Finally, the global mean pooling is used to obtain the feature vectors and different classifiers are used for different feature vectors. And the decision-level fusion is adopted to obtain more reliable predictions. The experimental results on the AID and NWPU-RESISC45 datasets show that the proposed method makes a significant improvement in terms of overall accuracies compared with the baselines. And the overall accuracies of our method on the two datasets are 97.49% and 95.20%, respectively, which achieves state-of-the-art performance. The code will be public at a Github repository available at https://github.com/Cbanyungong/JLMSAF.

Road extraction from synthetic aperture radar (SAR) images has attracted much attention in the field of remote sensing image processing. General road extraction algorithms, affected by shadows of buildings and trees, are prone to producing fragmented road segments. To improve the accuracy and completeness of road extraction, we propose a neural network-based algorithm which takes the connectivity and direction features of roads into consideration, named RoadSeg-CD. It consists of two branches: one is the main branch for road segmentation; the other is the auxiliary branch for learning road directions. In the main branch, a connectivity array is designed to utilize local contextual information and construct a connectivity loss based on the predicted probabilities of neighboring pixels. In the auxiliary branch, we proposed a novel road direction map, which is used for learning the directions of roads. The two branches are connected by specific feature fusion process, and the output from the main branch is taken as the road extraction result. Experiments on real radar images are implemented to validate the effectiveness of our method. The experimental results demonstrate that our method can obtain more continuous and more complete roads than several state-of-the-art road extraction algorithms.

Road extraction from remote-sensing images is of great significance for vehicle navigation and emergency insurance. However, the road information extracted in the remote-sensing image is discontinuous because the road in the image is often obscured by the shadows of trees or buildings. Moreover, due to the scale difference of roads in remote-sensing images, it remains a computational challenge to extract small-size roads from remote-sensing images. To address those problems, we propose a road extraction method based on adaptive global feature fusion (AGF-Net). First, a dilated convolution strip attention (DCSA) module is designed from the encoder–decoder structure. It consists of the dilated convolution and the strip attention module, which adaptively emphasizes relevant features in vertical and horizontal directions. Then, multiple global feature fusion modules (GFFM) in the skip connection are designed to supplement the decoder with road detail features, and we design a multi-scale strip convolution module (MSCM) to implement the GFFM module to obtain multi-scale road information. We compare AGF-Net to state-of-the-art methods and report their performance using standard evaluation metrics, including Intersection over Union (IoU), F1-score, precision, and recall. Our proposed AGF-Net achieves higher accuracy compared to other existing methods on the Massachusetts Road Dataset, DeepGlobe Road Dataset, CHN6-CUG Road Dataset, and BJRoad Dataset. The IoU obtained on these datasets are 0.679, 0.673, 0.567, and 0.637, respectively.

According to the road extraction from moderate and low resolution aerial image, this paper presents a fast method which is based on Sorting. In the initial stage of the method, an algorithm for detecting ridge or ribbon like linear features based on sorting and simple judgment scheme is adopted; after thinning the centerline, using the initial image road features to check the correctness of the result, then adjusting the centerline to ensure the roads' validity; at last, fitting the centerline based on the least square method and Newton method to get a proper road expression for user. Experiment showed, this method is simple to use, of high accuracy, after improvement can be used in the semi-automatic or automatic road extraction.

Road extraction from very high-resolution (VHR) satellite images plays an important role in the remote-sensing applications. Although tracing road features in satellite images has received much attention over the years, fully automated methods appear to be in their infancy. To tackle these limitations to some extent, this paper presents a novel object-based automatic road extraction method. The proposed method consists of five main steps. First, satellite images are segmented to generate objects. Then, two object-based filters are applied to compute object features to select road candidates. After that, the road class is extracted using the support vector machine (SVM) based on the extracted feature set. Finally, tensor voting (TV), active contour, and the geometrical information are integrated to eliminate road gaps and improve road smoothness. Experiments are conducted on nine test sites. It is experimentally demonstrated that the proposed method produces an excellent accuracy for the automatic road extraction from VHR satellite images.

Road information is an important data source of basic geographic database. Research on intelligent, automated road extraction is significant for studies on identification and location of objects from remote sensing image, mass GIS data acquisition and the update of electronic maps and spatial databases. Mathematical morphology (MM) developed since 1960s can simplify image structure, keep image features, remove redundant structure, and its operations are simple, flexible and fast. In this paper, roads are classified into four kinds: linear road, curvilinear road, crossing road, breakage road, based on MM strategy, combination with image threshold segment method, four road extraction strategies were proposed, experiments proved that these four kinds road can be well extracted.

Automated road extraction from satellite imagery for dynamic map updating has become a crucial research focus in remote sensing, where existing state-of-the-art Transformer-based methods exhibit two critical limitations: (1) inadequate precision in capturing tubular road patterns and (2) suboptimal computational efficiency on standard GPUs. To address these challenges, we propose TrMamba, a new Tracking-based Mamba architecture that combines the original Mamba’s efficiency with enhanced tubular road pattern recognition through two key innovations: a tubular road pattern tracking mechanism for continuous road feature extraction and a tracking selective scanning module for directional context modeling via adaptive attention. By integrating a novel tubular tracking mechanism into the Mamba’s selective scanning process, TrMamba fundamentally improves the original paradigm and achieves superior road topology encoding, as demonstrated by extensive experiments showing state-of-the-art performance across multiple remote sensing benchmarks in both accuracy and computational efficiency. The source code is available at: https://github.com/Apheliosa/TrMamba.

The analysis of corrosion images is crucial in materials science, where acquiring clear images is fundamental for subsequent analysis. The goal of deblurring metal corrosion images is to reconstruct clear images from degraded ones. To the best of our knowledge, this study introduces the first paired blurry-sharp image dataset specifically designed for the metal corrosion domain, filling a critical gap in the existing research. This innovative approach effectively addresses the unique challenges associated with deblurring metal corrosion images. We propose a novel metal corrosion images deblurring network (MCIDN) that employs a dual-domain attention mechanism, integrating both spatial and frequency domains to enhance image clarity. This innovative approach effectively addresses the unique challenges associated with deblurring metal corrosion images. While self-attention is widely used in visual tasks, its quadratic complexity often leads to high computational costs. To address this issue, we introduce a new spatial channel attention module (SCAM) that employs dynamic group convolutions to achieve self-attention, effectively integrating information from local regions and enhancing representation learning capabilities. Recognizing the critical role of frequency components in image restoration, we develop a frequency channel attention module (FCAM) that selectively focuses on different frequency components of images, thereby enhancing deblurring performance. These two attention modules are seamlessly integrated into our network. Compared to existing methods, our approach demonstrates superior performance on datasets of blurry metal corrosion images, achieving a peak signal-to-noise ratio (PSNR) of 32.8645 dB and a structural similarity (SSIM) of 0.9768. These metrics indicate that our method provides clearer and more detailed reconstructions, significantly enhancing the image quality.

Single Shot MultiBox Detector (SSD) method using multi-scale feature maps for object detection, showing outstanding performance in object detection task. However, as a one-stage detection method, it’s difficult for SSD methods to quickly notice significant areas of objects in the image. In the SSD network structure, feature maps of different scales are used to independently predict object, and there is a lack of interaction between low-level feature maps and high-level feature maps. In this paper we propose an enhanced SSD method using interactive multi-scale attention features (MA-SSD). Our method uses the attention mechanism to generate attention features of multiple scales and adds it to the original detection branch of the SSD method, which effectively enhances the feature representation ability and improves the detection accuracy. At the same time, the feature of different detection scales interacts with each other, and all the detection branches in our method have a parallel structure, which ensures the detection efficiency. Our proposed method achieves competitive performance on the public dataset PascalVOC.

Road extraction is an essential step in building autonomous navigation systems. Detecting road segments is challenging as they are of varying widths, bifurcated throughout the image, and are often occluded by terrain, cloud, or other weather conditions. Using just convolution neural networks (ConvNets) for this problem is not effective as it is inefficient at capturing distant dependencies between road segments in the image which is essential to extract road connectivity. To this end, we propose a Spatial and Interaction Space Graph Reasoning (SPIN) module which when plugged into a ConvNet performs reasoning over graphs constructed on spatial and interaction spaces projected from the feature maps. Reasoning over spatial space extracts dependencies between different spatial regions and other contextual information. Reasoning over a projected interaction space helps in appropriate delineation of roads from other topographies present in the image. Thus, SPIN extracts long-range dependencies between road segments and effectively delineates roads from other semantics. We also introduce a SPIN pyramid which performs SPIN graph reasoning across multiple scales to extract multi-scale features. We propose a network based on stacked hourglass modules and SPIN pyramid for road segmentation which achieves better performance compared to existing methods. Moreover, our method is computationally efficient and significantly boosts the convergence speed during training, making it feasible for applying on large-scale high-resolution aerial images. Code available at: https://github.com/wgcban/SPIN_RoadMapper.git.