Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2025, V. 22, No. 5, pp. 51-62
Segmentation of small objects in radar images using a graph-convolutional neural network implementation of quadtrees
A.M. Dostovalova
1 , A.K. Gorshenin
1 1 Federal Research Center “Computer Science and Control” RAS, Moscow, Russia
Accepted: 07.08.2025
DOI: 10.21046/2070-7401-2025-22-5-51-62
The paper proposes an architecture for a balanced neural network quadtree to solve the problem of segmenting small objects in radar images with insufficient training data. This architecture includes a pretrained convolutional encoder that generates additional features for each pixel in the image, as well as a graph-convolutional neural network that enhances the processing of spatial relationships in the data through an integrated probabilistic quadtree model. The graph part contains a branch-pruning block that detects similarities between pixels across different spatial resolutions. Additionally, there is a feature-processing unit designed for scaled images, and a custom loss function to improve the accuracy of separating unbalanced classes. The U-Net architecture was used for segmenting radar images from Sentinel-1 and High Resolution Synthetic Aperture Radar Images Dataset (HRSID). The balanced neural network quadtree demonstrated improved segmentation quality for smaller objects in both multi-class and binary segmentation (i.e., object detection against the background) compared to a basic neural network quadtree and vanilla U-Net. As a result, F1 scores for small object classes increased by 3.59% for binary segmentation and by 47.42% for multi-class segmentation. The developed approaches have potential to be applied to the problem of detection of small-size objects using superpixels on high-resolution images.
Keywords: neural quadtrees, probability-informed neural networks, graph convolution networks, SAR image segmentation, small objects
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