摘要
针对高分辨率遥感图像检索中手工特征难以准确描述图像的问题,提出聚合卷积神经网络(convolutional neural network,CNN)特征的方法来改进特征表达。首先,将预训练的CNN参数迁移到遥感图像,并针对不同尺寸的输入图像,提取表达局部信息的CNN特征;然后,对该CNN特征采用池化区域尺寸不同的均值池化和视觉词袋(bag of visual words,Bo VW) 2种聚合方法,分别得到池化特征和Bo VW特征;最后,将2种聚合特征用于遥感图像检索。实验结果表明:合理的输入图像尺寸能提高聚合特征的表达能力;当池化区域为特征图的60%~80%时,绝大多数池化特征的结果优于传统均值池化方法的结果;池化特征和Bo VW特征的最优平均归一化修改检索等级值比手工特征分别降低了27. 31%和21. 51%,因此,均值池化和Bo VW方法都能有效提高遥感图像的检索性能。
In the high-resolution remote sensing image retrieval,it is difficult for hand-crafted features to describe the images accurately.Thus a method based on aggregating convolutional neural network(CNN) features is proposed to improve the feature representation.First,the parameters from CNN pre-trained on large-scale datasets are transferred for remote sensing images.Given input images with different sizes,the CNN features which represent local information are extracted.Then,average pooling with different pooling region sizes and bag of visual words(BoVW) are adopted to aggregate the CNN features.Pooling features and BoVW features are obtained accordingly.Finally,the above two aggregation features are utilized for remote sensing image retrieval.Experimental results demonstrate that the input image with reasonable size is capable of improving the feature representation.When the pooling region size is between 60% and 80% of the feature map,the vast majority of the results of pooling features are superior to those of the traditional average pooling method.The optimal average normalized modified retrieval rank values of pooling feature and BoVW feature are 27.31% and 21.51% lower than those of hand-crafted feature.Therefore,both the average pooling and BoVW can improve the remote sensing image retrieval performance efficiently.
引文
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