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Deep Neural Networks for Remote Sensing Applications

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Remote Sensing Image Processing".

Deadline for manuscript submissions: closed (30 September 2020) | Viewed by 73512

Special Issue Editors


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Guest Editor
Soft Computing and Intelligent Information System Research Group, University of Granada, 18071 Granada, Spain
Interests: convolutional neural networks (CNNs); recurrent Neural Networks (RNNs); object detection; instance segmentation; super-resolution

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Co-Guest Editor
Multidisciplinary Institute for Environment Studies “Ramon Margalef”, University of Alicante, Edificio Nuevos Institutos, Carretera de San Vicente del Raspeig s/n, 03690 San Vicente del Raspeig, Alicante, Spain
Interests: deep learning; forest; desertification; LU/LC change; convolutional neural networks; ecology; generative adversarial networks; object-based image analysis; semantic segmentation; super-resolution
Special Issues, Collections and Topics in MDPI journals
Department of Computer Technology and Communications, Polytechnic School of Cáceres, University of Extremadura, 10003 Cáceres, Spain
Interests: hyperspectral image analysis; machine (deep) learning; neural networks; multisensor data fusion; high performance computing; cloud computing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In recent years, several types of remotely sensed data, e.g., optical multi-spectral and hyper-spectral images, Synthetic Aperture Radar (SAR) and in many cases with extensive time series are increasingly available. In fact, several new Earth Online missions such as, the HyspIRI project developed by the NASA, the German EnMAP or the Italian PRISMA program, have increased the flow of generated remotely sensed data. All these remotely sensed data is motivating the development of large repositories and, most importantly, the development of advanced methods and algorithms for data analysis and processing.

On the other hand, Deep Neural Networks (DNNs), commonly called Deep Learning (DL) models, are showing very high potential in the recognition of spatial and temporal patterns in a wide range of remotely sensed applications (e.g., in scene classification, object detection, spectral unmixing, spatial super-resolution, pixel classification, dimensionality reduction, etc.), providing a great variety of algorithms, procedures and models, under different learning strategies (supervised, unsupervised, semi-supervised). In particular, Convolutional Neural Networks (CNNs), a type of DNNs, currently constitutes the-state-of-the art in image classification, object detection and instance segmentation. Generative adversarial networks (GANs) are showing promising results in the mapping of the terrestrial surface and in super-resolution problems. Recurrent Neural Networks (RNNs) are also showing good results in identifying patterns in time series and in forecasting meteorological events. 

However, due to the huge amount of parameters that need to be learned by DL models, the complex nature of DL models, the complexity of the remotely sensed data itself (e.g., high dimensionality) and the lack of labeled datasets, these approaches must deal with important problems, which can lead to inadequate generalization and loss of accuracy.

This Special Issue welcomes papers that explore novel and challenging applications by analyzing multi-band images acquired from diverse sensors using one or a combination of several Deep Learning models. We welcome topics that include but not limited to the following:

  • Labeled dataset of unmanned aerial vehicle, aerial or satellite multi-band images;
  • Dimensionality reduction;
  • Feature extraction;
  • Image fusion;
  • Image reconstruction;
  • Spectral unmixing methods;
  • Remotely sensed image classification;
  • Object detection in remotely sensed data, e.g., for designing new counting methods;
  • Instance segmentation in remotely sensing data, e.g., for the delimitation of vegetation individuals, wildlife, catastrophic events, meteorological events;
  • Adversarial generative networks, e.g., for super-resolution problems, classification of terrestrial surface, generation of synthesized images to fill gaps in clouds;
  • Detection of anomalies in time series;
  • Predictions, e.g., predicting specific climatic or polluting events, evolution of natural areas, changes in cities or crops;
  • New problem applications addressed with deep learning models;

Dr. Siham Tabik

Dr. Emilio Guirado

Dr. Juan Mario Haut

Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Multi-band and Multi-spectral images; aerial and satellite images; deep learning; neural network; image classification; object detection; instance segmentation; anomalies detection

Published Papers (13 papers)

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Research

30 pages, 33260 KiB  
Article
Individual Palm Tree Detection Using Deep Learning on RGB Imagery to Support Tree Inventory
by María Culman, Stephanie Delalieux and Kristof Van Tricht
Remote Sens. 2020, 12(21), 3476; https://doi.org/10.3390/rs12213476 - 22 Oct 2020
Cited by 29 | Viewed by 6784
Abstract
Phoenix palms cover more than 1.3 million hectares in the Mediterranean, Middle East, and North Africa regions and they represent highly valued assets for economic, environmental, and cultural purposes. Despite their importance, information on the number of palm trees and the palm distribution [...] Read more.
Phoenix palms cover more than 1.3 million hectares in the Mediterranean, Middle East, and North Africa regions and they represent highly valued assets for economic, environmental, and cultural purposes. Despite their importance, information on the number of palm trees and the palm distribution across different scenes is difficult to obtain and, therefore, limited. In this work, we present the first region-wide spatial inventory of Phoenix dactylifera (date palm) and Phoenix canariensis (canary palm) trees, based on remote imagery from the Alicante province in Spain. A deep learning architecture that was based on convolutional neural networks (CNN) was implemented to generate a detection model able to locate and classify individual palms trees from aerial high-resolution RGB images. When considering that creating large labeled image datasets is a constraint in object detection applied to remote sensing data, as a strategy for pre-training detection models on a similar task, imagery and palm maps from the autonomous community of the Canary Islands were used. Subsequently, these models were transferred for re-training with imagery from Alicante. The best performing model was capable of mapping Phoenix palms in different scenes, with a changeable appearance, and with varied ages, achieving a mean average precision (mAP) value of 0.861. In total, 511,095 Phoenix palms with a probability score above 0.5 were detected over an area of 5816 km2. The detection model, which was obtained from an out-of-the-box object detector, RetinaNet, provides a fast and straightforward method to map isolated and densely distributed date and canary palms—and other Phoenix palms. The inventory of palm trees established here provides quantitative information on Phoenix palms distribution, which could be used as a baseline for long-term monitoring of palms’ conditions. In addition to boosting palm tree inventory across multiple landscapes at a large scale, the detection model demonstrates how image processing techniques that are based on deep learning leverage image understanding from remote sensing data. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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19 pages, 3552 KiB  
Article
Small Object Detection in Remote Sensing Images Based on Super-Resolution with Auxiliary Generative Adversarial Networks
by Luc Courtrai, Minh-Tan Pham and Sébastien Lefèvre
Remote Sens. 2020, 12(19), 3152; https://doi.org/10.3390/rs12193152 - 25 Sep 2020
Cited by 66 | Viewed by 8122
Abstract
This article tackles the problem of detecting small objects in satellite or aerial remote sensing images by relying on super-resolution to increase image spatial resolution, thus the size and details of objects to be detected. We show how to improve the super-resolution framework [...] Read more.
This article tackles the problem of detecting small objects in satellite or aerial remote sensing images by relying on super-resolution to increase image spatial resolution, thus the size and details of objects to be detected. We show how to improve the super-resolution framework starting from the learning of a generative adversarial network (GAN) based on residual blocks and then its integration into a cycle model. Furthermore, by adding to the framework an auxiliary network tailored for object detection, we considerably improve the learning and the quality of our final super-resolution architecture, and more importantly increase the object detection performance. Besides the improvement dedicated to the network architecture, we also focus on the training of super-resolution on target objects, leading to an object-focused approach. Furthermore, the proposed strategies do not depend on the choice of a baseline super-resolution framework, hence could be adopted for current and future state-of-the-art models. Our experimental study on small vehicle detection in remote sensing data conducted on both aerial and satellite images (i.e., ISPRS Potsdam and xView datasets) confirms the effectiveness of the improved super-resolution methods to assist with the small object detection tasks. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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23 pages, 11869 KiB  
Article
Crop Classification Method Based on Optimal Feature Selection and Hybrid CNN-RF Networks for Multi-Temporal Remote Sensing Imagery
by Shuting Yang, Lingjia Gu, Xiaofeng Li, Tao Jiang and Ruizhi Ren
Remote Sens. 2020, 12(19), 3119; https://doi.org/10.3390/rs12193119 - 23 Sep 2020
Cited by 62 | Viewed by 6278
Abstract
Although efforts and progress have been made in crop classification using optical remote sensing images, it is still necessary to make full use of the high spatial, temporal, and spectral resolutions of remote sensing images. However, with the increasing volume of remote sensing [...] Read more.
Although efforts and progress have been made in crop classification using optical remote sensing images, it is still necessary to make full use of the high spatial, temporal, and spectral resolutions of remote sensing images. However, with the increasing volume of remote sensing data, a key emerging issue in the field of crop classification is how to find useful information from massive data to balance classification accuracy and processing time. To address this challenge, we developed a novel crop classification method, combining optimal feature selection (OFSM) with hybrid convolutional neural network-random forest (CNN-RF) networks for multi-temporal optical remote sensing images. This research used 234 features including spectral, segmentation, color, and texture features from three scenes of Sentinel-2 images to identify crop types in the Jilin province of northeast China. To effectively extract the effective features of remote sensing data with lower time requirements, the use of OFSM was proposed with the results compared with two traditional feature selection methods (TFSM): random forest feature importance selection (RF-FI) and random forest recursive feature elimination (RF-RFE). Although the time required for OFSM was 26.05 s, which was between RF-FI with 1.97 s and RF-RFE with 132.54 s, OFSM outperformed RF-FI and RF-RFE in terms of the overall accuracy (OA) of crop classification by 4% and 0.3%, respectively. On the basis of obtaining effective feature information, to further improve the accuracy of crop classification we designed two hybrid CNN-RF networks to leverage the advantages of one-dimensional convolution (Conv1D) and Visual Geometry Group (VGG) with random forest (RF), respectively. Based on the selected optimal features using OFSM, four networks were tested for comparison: Conv1D-RF, VGG-RF, Conv1D, and VGG. Conv1D-RF achieved the highest OA at 94.27% as compared with VGG-RF (93.23%), Conv1D (92.59%), and VGG (91.89%), indicating that the Conv1D-RF method with optimal feature input provides an effective and efficient method of time series representation for multi-temporal crop-type classification. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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25 pages, 7082 KiB  
Article
Anchor-free Convolutional Network with Dense Attention Feature Aggregation for Ship Detection in SAR Images
by Fei Gao, Yishan He, Jun Wang, Amir Hussain and Huiyu Zhou
Remote Sens. 2020, 12(16), 2619; https://doi.org/10.3390/rs12162619 - 13 Aug 2020
Cited by 53 | Viewed by 4309
Abstract
In recent years, with the improvement of synthetic aperture radar (SAR) imaging resolution, it is urgent to develop methods with higher accuracy and faster speed for ship detection in high-resolution SAR images. Among all kinds of methods, deep-learning-based algorithms bring promising performance due [...] Read more.
In recent years, with the improvement of synthetic aperture radar (SAR) imaging resolution, it is urgent to develop methods with higher accuracy and faster speed for ship detection in high-resolution SAR images. Among all kinds of methods, deep-learning-based algorithms bring promising performance due to end-to-end detection and automated feature extraction. However, several challenges still exist: (1) standard deep learning detectors based on anchors have certain unsolved problems, such as tuning of anchor-related parameters, scale-variation and high computational costs. (2) SAR data is huge but the labeled data is relatively small, which may lead to overfitting in training. (3) To improve detection speed, deep learning detectors generally detect targets based on low-resolution features, which may cause missed detections for small targets. In order to address the above problems, an anchor-free convolutional network with dense attention feature aggregation is proposed in this paper. Firstly, we use a lightweight feature extractor to extract multiscale ship features. The inverted residual blocks with depth-wise separable convolution reduce the network parameters and improve the detection speed. Secondly, a novel feature aggregation scheme called dense attention feature aggregation (DAFA) is proposed to obtain a high-resolution feature map with multiscale information. By combining the multiscale features through dense connections and iterative fusions, DAFA improves the generalization performance of the network. In addition, an attention block, namely spatial and channel squeeze and excitation (SCSE) block is embedded in the upsampling process of DAFA to enhance the salient features of the target and suppress the background clutters. Third, an anchor-free detector, which is a center-point-based ship predictor (CSP), is adopted in this paper. CSP regresses the ship centers and ship sizes simultaneously on the high-resolution feature map to implement anchor-free and nonmaximum suppression (NMS)-free ship detection. The experiments on the AirSARShip-1.0 dataset demonstrate the effectiveness of our method. The results show that the proposed method outperforms several mainstream detection algorithms in both accuracy and speed. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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29 pages, 13310 KiB  
Article
Segmentation of Vegetation and Flood from Aerial Images Based on Decision Fusion of Neural Networks
by Loretta Ichim and Dan Popescu
Remote Sens. 2020, 12(15), 2490; https://doi.org/10.3390/rs12152490 - 03 Aug 2020
Cited by 7 | Viewed by 4185
Abstract
The detection and evaluation of flood damage in rural zones are of great importance for farmers, local authorities, and insurance companies. To this end, the paper proposes an efficient system based on five neural networks to assess the degree of flooding and the [...] Read more.
The detection and evaluation of flood damage in rural zones are of great importance for farmers, local authorities, and insurance companies. To this end, the paper proposes an efficient system based on five neural networks to assess the degree of flooding and the remaining vegetation. After a previous analysis the following neural networks were selected as primary classifiers: you only look once network (YOLO), generative adversarial network (GAN), AlexNet, LeNet, and residual network (ResNet). Their outputs were connected in a decision fusion scheme, as a new convolutional layer, considering two sets of components: (a) the weights, corresponding to the proven accuracy of the primary neural networks in the validation phase, and (b) the probabilities generated by the neural networks as primary classification results in the operational (testing) phase. Thus, a subjective behavior (individual interpretation of single neural networks) was transformed into a more objective behavior (interpretation based on fusion of information). The images, difficult to be segmented, were obtained from an unmanned aerial vehicle photogrammetry flight after a moderate flood in a rural region of Romania and make up our database. For segmentation and evaluation of the flooded zones and vegetation, the images were first decomposed in patches and, after classification the resulting marked patches were re-composed in segmented images. From the performance analysis point of view, better results were obtained with the proposed system than the neural networks taken separately and with respect to some works from the references. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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22 pages, 4284 KiB  
Article
Deep Learning and Adaptive Graph-Based Growing Contours for Agricultural Field Extraction
by Matthias P. Wagner and Natascha Oppelt
Remote Sens. 2020, 12(12), 1990; https://doi.org/10.3390/rs12121990 - 21 Jun 2020
Cited by 16 | Viewed by 3004
Abstract
Field mapping and information on agricultural landscapes is of increasing importance for many applications. Monitoring schemes and national cadasters provide a rich source of information but their maintenance and regular updating is costly and labor-intensive. Automatized mapping of fields based on remote sensing [...] Read more.
Field mapping and information on agricultural landscapes is of increasing importance for many applications. Monitoring schemes and national cadasters provide a rich source of information but their maintenance and regular updating is costly and labor-intensive. Automatized mapping of fields based on remote sensing imagery may aid in this task and allow for a faster and more regular observation. Although remote sensing has seen extensive use in agricultural research topics, such as plant health monitoring, crop type classification, yield prediction, and irrigation, field delineation and extraction has seen comparatively little research interest. In this study, we present a field boundary detection technique based on deep learning and a variety of image features, and combine it with the graph-based growing contours (GGC) method to extract agricultural fields in a study area in northern Germany. The boundary detection step only requires red, green, and blue (RGB) data and is therefore largely independent of the sensor used. We compare different image features based on color and luminosity information and evaluate their usefulness for the task of field boundary detection. A model based on texture metrics, gradient information, Hessian matrix eigenvalues, and local statistics showed good results with accuracies up to 88.2%, an area under the ROC curve (AUC) of up to 0.94, and F1 score of up to 0.88. The exclusive use of these universal image features may also facilitate transferability to other regions. We further present modifications to the GGC method intended to aid in upscaling of the method through process acceleration with a minimal effect on results. We combined the boundary detection results with the GGC method for field polygon extraction. Results were promising, with the new GGC version performing similarly or better than the original version while experiencing an acceleration of 1.3× to 2.3× on different subsets and input complexities. Further research may explore other applications of the GGC method outside agricultural remote sensing and field extraction. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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25 pages, 18471 KiB  
Article
CORN: An Alternative Way to Utilize Time-Series Data of SAR Images in Newly Built Construction Detection
by Raveerat Jaturapitpornchai, Poompat Rattanasuwan, Masashi Matsuoka and Ryosuke Nakamura
Remote Sens. 2020, 12(6), 990; https://doi.org/10.3390/rs12060990 - 19 Mar 2020
Cited by 3 | Viewed by 2574
Abstract
The limitations in obtaining sufficient datasets for training deep learning networks is preventing many applications from achieving accurate results, especially when detecting new constructions using time-series satellite imagery, since this requires at least two images of the same scene and it must contain [...] Read more.
The limitations in obtaining sufficient datasets for training deep learning networks is preventing many applications from achieving accurate results, especially when detecting new constructions using time-series satellite imagery, since this requires at least two images of the same scene and it must contain new constructions in it. To tackle this problem, we introduce Chronological Order Reverse Network (CORN)—an architecture for detecting newly built constructions in time-series SAR images that does not require a large quantity of training data. The network uses two U-net adaptations to learn the changes between images from both Time 1–Time 2 and Time 2–Time 1 formats, which allows it to learn double the amount of changes in different perspectives. We trained the network with 2028 pairs of 256 × 256 pixel SAR images from ALOS-PALSAR, totaling 4056 pairs for the network to learn from, since it learns from both Time 1–Time 2 and Time 2–Time 1. As a result, the network can detect new constructions more accurately, especially at the building boundary, compared to the original U-net trained by the same amount of training data. The experiment also shows that the model trained with CORN can be used with images from Sentinel-1. The source code is available at https://github.com/Raveerat-titech/CORN. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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24 pages, 7151 KiB  
Article
HQ-ISNet: High-Quality Instance Segmentation for Remote Sensing Imagery
by Hao Su, Shunjun Wei, Shan Liu, Jiadian Liang, Chen Wang, Jun Shi and Xiaoling Zhang
Remote Sens. 2020, 12(6), 989; https://doi.org/10.3390/rs12060989 - 19 Mar 2020
Cited by 72 | Viewed by 6265
Abstract
Instance segmentation in high-resolution (HR) remote sensing imagery is one of the most challenging tasks and is more difficult than object detection and semantic segmentation tasks. It aims to predict class labels and pixel-wise instance masks to locate instances in an image. However, [...] Read more.
Instance segmentation in high-resolution (HR) remote sensing imagery is one of the most challenging tasks and is more difficult than object detection and semantic segmentation tasks. It aims to predict class labels and pixel-wise instance masks to locate instances in an image. However, there are rare methods currently suitable for instance segmentation in the HR remote sensing images. Meanwhile, it is more difficult to implement instance segmentation due to the complex background of remote sensing images. In this article, a novel instance segmentation approach of HR remote sensing imagery based on Cascade Mask R-CNN is proposed, which is called a high-quality instance segmentation network (HQ-ISNet). In this scheme, the HQ-ISNet exploits a HR feature pyramid network (HRFPN) to fully utilize multi-level feature maps and maintain HR feature maps for remote sensing images’ instance segmentation. Next, to refine mask information flow between mask branches, the instance segmentation network version 2 (ISNetV2) is proposed to promote further improvements in mask prediction accuracy. Then, we construct a new, more challenging dataset based on the synthetic aperture radar (SAR) ship detection dataset (SSDD) and the Northwestern Polytechnical University very-high-resolution 10-class geospatial object detection dataset (NWPU VHR-10) for remote sensing images instance segmentation which can be used as a benchmark for evaluating instance segmentation algorithms in the high-resolution remote sensing images. Finally, extensive experimental analyses and comparisons on the SSDD and the NWPU VHR-10 dataset show that (1) the HRFPN makes the predicted instance masks more accurate, which can effectively enhance the instance segmentation performance of the high-resolution remote sensing imagery; (2) the ISNetV2 is effective and promotes further improvements in mask prediction accuracy; (3) our proposed framework HQ-ISNet is effective and more accurate for instance segmentation in the remote sensing imagery than the existing algorithms. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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19 pages, 7362 KiB  
Article
Estimation of Hourly Rainfall during Typhoons Using Radar Mosaic-Based Convolutional Neural Networks
by Chih-Chiang Wei and Po-Yu Hsieh
Remote Sens. 2020, 12(5), 896; https://doi.org/10.3390/rs12050896 - 10 Mar 2020
Cited by 16 | Viewed by 3824
Abstract
Taiwan is located at the junction of the tropical and subtropical climate zones adjacent to the Eurasian continent and Pacific Ocean. The island frequently experiences typhoons that engender severe natural disasters and damage. Therefore, efficiently estimating typhoon rainfall in Taiwan is essential. This [...] Read more.
Taiwan is located at the junction of the tropical and subtropical climate zones adjacent to the Eurasian continent and Pacific Ocean. The island frequently experiences typhoons that engender severe natural disasters and damage. Therefore, efficiently estimating typhoon rainfall in Taiwan is essential. This study examined the efficacy of typhoon rainfall estimation. Radar images released by the Central Weather Bureau were used to estimate instantaneous rainfall. Additionally, two proposed neural network-based architectures, namely a radar mosaic-based convolutional neural network (RMCNN) and a radar mosaic-based multilayer perceptron (RMMLP), were used to estimate typhoon rainfall, and the commonly applied Marshall–Palmer Z-R relationship (Z-R_MP) and a reformulated Z-R relationship at each site (Z-R_station) were adopted to construct benchmark models. Monitoring stations in Hualien, Sun Moon Lake, and Taichung were selected as the experimental stations in Eastern, Central, and Western Taiwan, respectively. This study compared the performance of the models in predicting rainfall at the three stations, and the results are outlined as follows: at the Hualien station, the estimations of the RMCNN, RMMLP, Z-R_MP, and Z-R_station models were mostly identical to the observed rainfall, and all models estimated an increase during peak rainfall on the hyetographs, but the peak values were underestimated. At the Sun Moon Lake and Taichung stations, however, the estimations of the four models were considerably inconsistent in terms of overall rainfall rates, peak rainfall, and peak rainfall arrival times on the hyetographs. The relative root mean squared error for overall rainfall rates of all stations was smallest when computed using RMCNN (0.713), followed by those computed using RMMLP (0.848), Z-R_MP (1.030), and Z-R_station (1.392). Moreover, RMCNN yielded the smallest relative error for peak rainfall (0.316), followed by RMMLP (0.379), Z-R_MP (0.402), and Z-R_station (0.688). RMCNN computed the smallest relative error for the peak rainfall arrival time (1.507 h), followed by RMMLP (2.673 h), Z-R_MP (2.917 h), and Z-R_station (3.250 h). The results revealed that the RMCNN model in combination with radar images could efficiently estimate typhoon rainfall. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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16 pages, 6951 KiB  
Article
Multi-Scale Context Aggregation for Semantic Segmentation of Remote Sensing Images
by Jing Zhang, Shaofu Lin, Lei Ding and Lorenzo Bruzzone
Remote Sens. 2020, 12(4), 701; https://doi.org/10.3390/rs12040701 - 24 Feb 2020
Cited by 105 | Viewed by 8271
Abstract
The semantic segmentation of remote sensing images (RSIs) is important in a variety of applications. Conventional encoder-decoder-based convolutional neural networks (CNNs) use cascade pooling operations to aggregate the semantic information, which results in a loss of localization accuracy and in the preservation of [...] Read more.
The semantic segmentation of remote sensing images (RSIs) is important in a variety of applications. Conventional encoder-decoder-based convolutional neural networks (CNNs) use cascade pooling operations to aggregate the semantic information, which results in a loss of localization accuracy and in the preservation of spatial details. To overcome these limitations, we introduce the use of the high-resolution network (HRNet) to produce high-resolution features without the decoding stage. Moreover, we enhance the low-to-high features extracted from different branches separately to strengthen the embedding of scale-related contextual information. The low-resolution features contain more semantic information and have a small spatial size; thus, they are utilized to model the long-term spatial correlations. The high-resolution branches are enhanced by introducing an adaptive spatial pooling (ASP) module to aggregate more local contexts. By combining these context aggregation designs across different levels, the resulting architecture is capable of exploiting spatial context at both global and local levels. The experimental results obtained on two RSI datasets show that our approach significantly improves the accuracy with respect to the commonly used CNNs and achieves state-of-the-art performance. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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29 pages, 1340 KiB  
Article
Inference in Supervised Spectral Classifiers for On-Board Hyperspectral Imaging: An Overview
by Adrián Alcolea, Mercedes E. Paoletti, Juan M. Haut, Javier Resano and Antonio Plaza
Remote Sens. 2020, 12(3), 534; https://doi.org/10.3390/rs12030534 - 06 Feb 2020
Cited by 33 | Viewed by 3701
Abstract
Machine learning techniques are widely used for pixel-wise classification of hyperspectral images. These methods can achieve high accuracy, but most of them are computationally intensive models. This poses a problem for their implementation in low-power and embedded systems intended for on-board processing, in [...] Read more.
Machine learning techniques are widely used for pixel-wise classification of hyperspectral images. These methods can achieve high accuracy, but most of them are computationally intensive models. This poses a problem for their implementation in low-power and embedded systems intended for on-board processing, in which energy consumption and model size are as important as accuracy. With a focus on embedded and on-board systems (in which only the inference step is performed after an off-line training process), in this paper we provide a comprehensive overview of the inference properties of the most relevant techniques for hyperspectral image classification. For this purpose, we compare the size of the trained models and the operations required during the inference step (which are directly related to the hardware and energy requirements). Our goal is to search for appropriate trade-offs between on-board implementation (such as model size and energy consumption) and classification accuracy. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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23 pages, 11694 KiB  
Article
A Multi-Scale and Multi-Level Spectral-Spatial Feature Fusion Network for Hyperspectral Image Classification
by Caihong Mu, Zhen Guo and Yi Liu
Remote Sens. 2020, 12(1), 125; https://doi.org/10.3390/rs12010125 - 01 Jan 2020
Cited by 28 | Viewed by 5348
Abstract
Extracting spatial and spectral features through deep neural networks has become an effective means of classification of hyperspectral images. However, most networks rarely consider the extraction of multi-scale spatial features and cannot fully integrate spatial and spectral features. In order to solve these [...] Read more.
Extracting spatial and spectral features through deep neural networks has become an effective means of classification of hyperspectral images. However, most networks rarely consider the extraction of multi-scale spatial features and cannot fully integrate spatial and spectral features. In order to solve these problems, this paper proposes a multi-scale and multi-level spectral-spatial feature fusion network (MSSN) for hyperspectral image classification. The network uses the original 3D cube as input data and does not need to use feature engineering. In the MSSN, using different scale neighborhood blocks as the input of the network, the spectral-spatial features of different scales can be effectively extracted. The proposed 3D–2D alternating residual block combines the spectral features extracted by the three-dimensional convolutional neural network (3D-CNN) with the spatial features extracted by the two-dimensional convolutional neural network (2D-CNN). It not only achieves the fusion of spectral features and spatial features but also achieves the fusion of high-level features and low-level features. Experimental results on four hyperspectral datasets show that this method is superior to several state-of-the-art classification methods for hyperspectral images. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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21 pages, 34669 KiB  
Article
Mask OBB: A Semantic Attention-Based Mask Oriented Bounding Box Representation for Multi-Category Object Detection in Aerial Images
by Jinwang Wang, Jian Ding, Haowen Guo, Wensheng Cheng, Ting Pan and Wen Yang
Remote Sens. 2019, 11(24), 2930; https://doi.org/10.3390/rs11242930 - 06 Dec 2019
Cited by 129 | Viewed by 9128
Abstract
Object detection in aerial images is a fundamental yet challenging task in remote sensing field. As most objects in aerial images are in arbitrary orientations, oriented bounding boxes (OBBs) have a great superiority compared with traditional horizontal bounding boxes (HBBs). However, the regression-based [...] Read more.
Object detection in aerial images is a fundamental yet challenging task in remote sensing field. As most objects in aerial images are in arbitrary orientations, oriented bounding boxes (OBBs) have a great superiority compared with traditional horizontal bounding boxes (HBBs). However, the regression-based OBB detection methods always suffer from ambiguity in the definition of learning targets, which will decrease the detection accuracy. In this paper, we provide a comprehensive analysis of OBB representations and cast the OBB regression as a pixel-level classification problem, which can largely eliminate the ambiguity. The predicted masks are subsequently used to generate OBBs. To handle huge scale changes of objects in aerial images, an Inception Lateral Connection Network (ILCN) is utilized to enhance the Feature Pyramid Network (FPN). Furthermore, a Semantic Attention Network (SAN) is adopted to provide the semantic feature, which can help distinguish the object of interest from the cluttered background effectively. Empirical studies show that the entire method is simple yet efficient. Experimental results on two widely used datasets, i.e., DOTA and HRSC2016, demonstrate that the proposed method outperforms state-of-the-art methods. Full article
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
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