Pruning Multi-Scale Multi-Branch Network for Small-Sample Hyperspectral Image Classification

In recent years, the use of deep learning models has developed rapidly in the field of hyperspectral image (HSI) classification. However, most network models cannot make full use of the rich spatial-spectral features in hyperspectral images, being disadvantaged by their complex models and low classification accuracy for small-sample data. To address these problems, we present a lightweight multi-scale multi-branch hybrid convolutional network for small-sample classification. The network contains two new modules, a pruning multi-scale multi-branch block (PMSMBB) and a 3D-PMSMBB, each of which contains a multi-branch part and a pruning part. Each branch of the multi-branch part contains a convolutional kernel of different scales. In the training phase, the multi-branch part can extract rich feature information through different perceptual fields using the asymmetric convolution feature, which can effectively improve the classification accuracy of the model. To make the model lighter, pruning is introduced in the master branch of each multi-branch module, and the pruning part can remove the insignificant parameters without affecting the learning of the multi-branch part, achieving a light weight model. In the testing phase, the multi-branch part and the pruning part are jointly transformed into one convolution, without adding any extra parameters to the network. The study method was tested on three datasets: Indian Pines (IP), Pavia University (PU), and Salinas (SA). Compared with other advanced classification models, this pruning multi-scale multi-branch hybrid convolutional network (PMSMBN) had significant advantages in HSI small-sample classification. For instance, in the SA dataset with multiple crops, only 1% of the samples were selected for training, and the proposed method achieved an overall accuracy of 99.70%.