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arXiv 2306.15868cs.LGcs.CVeess.IV

GraSS:面向遥感图像语义分割的梯度引导采样策略对比学习

GraSS: Contrastive Learning with Gradient Guided Sampling Strategy for Remote Sensing Image Semantic Segmentation

Central South University(中南大学);Xiangjiang Laboratory(湘江实验室)

Zhaoyang Zhang, Zhen Ren, Chao Tao, Yunsheng Zhang, Chengli Peng, Haifeng Li

AI总结:

针对遥感图像语义分割中自监督对比学习的正样本混淆和特征适应偏差问题,本文提出GraSS方法,利用对比损失梯度定位单一地物区域并引导采样构建新样本,在三个数据集上相比七种基线平均提升1.57%的mIoU。

摘要:

自监督对比学习(SSCL)在遥感图像(RSI)理解中取得了重要里程碑。其本质在于设计一个无监督实例判别 pretext 任务,从大量无标签图像中提取对下游任务有益的图像特征。然而,现有的基于实例判别的 SSCL 在应用于 RSI 语义分割任务时存在两个局限:1)正样本混淆问题;2)特征适应偏差。当应用于需要像素级或对象级特征的语义分割任务时,它会引入特征适应偏差。在本研究中,我们观察到判别信息可以通过无监督对比损失的梯度映射到 RSI 中的特定区域,这些特定区域往往包含单一地物。基于此,我们提出了面向 RSI 语义分割的梯度引导采样策略对比学习(GraSS)。GraSS 包含两个阶段:实例判别预热(ID warm-up)和梯度引导采样对比训练(GS training)。ID warm-up 旨在为对比损失梯度提供初始判别信息。GS training 阶段旨在利用对比损失梯度中包含的判别信息,自适应地选择 RSI 图像块中包含更多单一地物的区域,以构建新的正样本和负样本。在三个公开数据集上的实验结果表明,GraSS 有效提升了 SSCL 在高分辨率 RSI 语义分割中的性能。与来自五种不同类型 SSCL 的七个基线方法相比,GraSS 在平均交并比指标上实现了平均 1.57% 的提升,最大提升达 3.58%。源代码可在 https://github.com/GeoX-Lab/GraSS 获取。

英文摘要:

Self-supervised contrastive learning (SSCL) has achieved significant milestones in remote sensing image (RSI) understanding. Its essence lies in designing an unsupervised instance discrimination pretext task to extract image features from a large number of unlabeled images that are beneficial for downstream tasks. However, existing instance discrimination based SSCL suffer from two limitations when applied to the RSI semantic segmentation task: 1) Positive sample confounding issue; 2) Feature adaptation bias. It introduces a feature adaptation bias when applied to semantic segmentation tasks that require pixel-level or object-level features. In this study, We observed that the discrimination information can be mapped to specific regions in RSI through the gradient of unsupervised contrastive loss, these specific regions tend to contain singular ground objects. Based on this, we propose contrastive learning with Gradient guided Sampling Strategy (GraSS) for RSI semantic segmentation. GraSS consists of two stages: Instance Discrimination warm-up (ID warm-up) and Gradient guided Sampling contrastive training (GS training). The ID warm-up aims to provide initial discrimination information to the contrastive loss gradients. The GS training stage aims to utilize the discrimination information contained in the contrastive loss gradients and adaptively select regions in RSI patches that contain more singular ground objects, in order to construct new positive and negative samples. Experimental results on three open datasets demonstrate that GraSS effectively enhances the performance of SSCL in high-resolution RSI semantic segmentation. Compared to seven baseline methods from five different types of SSCL, GraSS achieves an average improvement of 1.57\% and a maximum improvement of 3.58\% in terms of mean intersection over the union. The source code is available at https://github.com/GeoX-Lab/GraSS

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