A review of small object detection based on deep learning

Small object detection is widely used in a variety of fields such as automatic driving, UAV-based object detection, and aerial image detection. However, small objects carry limited information, making it difficult for detectors to detect small objects. In recent years, the development of deep learning has significantly improved the performance of small object detection. This paper provides a comprehensive review to help further the development of small target detection. We summarize the challenges related to small object detection and analyze solutions to these challenges in existing works, including integrating the feature at different layers, enriching available information, balancing the number of positive and negative samples for small objects, and increasing sufficient small object instances. We discuss related methods developed in three application areas, including automatic driving, UAV search and rescue, and aerial image detection. In addition, we thoroughly analyze the performance of typical small object detection methods on popular datasets. Finally, based on the comprehensive review of small object detection methods, we point out possible research directions for future studies.