Anchor-free Convolutional Network with Dense Attention Feature Aggregation for Ship Detection in SAR Images

Fei Gao, Yishan He, Jun Wang*, Amir Hussain, Huiyu Zhou

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
1 Downloads (Pure)

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 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.

Original languageEnglish
Article number2619
Number of pages25
JournalRemote Sensing
Volume12
Issue number16
DOIs
Publication statusPublished - Aug 2020
Externally publishedYes

Bibliographical note

Funding Information:
Funding: This research was funded by the National Natural Science Foundation of China, Grant Nos. 61771027, 61071139, 61471019, 61501011 and 61171122. A.H. was supported by the U.K. Engineering and Physical Sciences Research Council (EPSRC) Grant No. EP/M026981/1. H.Z. was supported by the U.K. EPSRC under Grant EP/N011074/1, Royal Society-Newton Advanced Fellowship under Grant NA160342 and the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska Curie Grant Agreement No. 720325.

Funding Information:
This research was funded by the National Natural Science Foundation of China, Grant Nos. 61771027, 61071139, 61471019, 61501011 and 61171122. A.H. was supported by the U.K. Engineering and Physical Sciences Research Council (EPSRC) Grant No. EP/M026981/1. H.Z. was supported by the U.K. EPSRC under Grant EP/N011074/1, Royal Society-Newton Advanced Fellowship under Grant NA160342 and the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska Curie Grant Agreement No. 720325.

Publisher Copyright:
© 2020 by the authors.

Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.

Keywords

  • Anchor-free
  • Attention mechanism
  • Convolutional neural networks (CNN)
  • Feature aggregation
  • Ship detection
  • Synthetic aperture radar (SAR)

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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