Satellite cloud image retrieval based on deep metric learning

Due to the traditional cloud image retrieval methods are difficult to obtain ideal retrieval accuracy and retrieval efficiency, a cloud image retrieval method based on deep metric learning is proposed. Firstly, a residual 3D-2D convolutional neural network is designed to extract spatial and spectral features of cloud images. Since the features extracted by the traditional classify-based deep network may have greater differences intra-classes than inter-classes, the triplet strategy is used to train the network, and the cloud images are mapped into the metric space according to the similarity between cloud images, so that the distance of similar cloud images in the embedded space is smaller than that of non-similar cloud images. In model training, the convergence performance of traditional triplet loss is improved and the precision of cloud image retrieval is increased by adding a constraint on the distance between positive sample pairs to the lossless triplet loss function. Finally, through hash learning, the cloud features in the metric space are transformed into hash codes, so as to ensure the retrieval accuracy and improve the retrieval efficiency. Experimental results show that the mean average precision (mAP) of the proposed algorithm is 75.14% and 80.14% for the southeast coastal cloud image dataset and the northern hemisphere cloud image dataset respectively, which is superior to other comparison methods.