Automatic Design of CNNs via Differentiable Neural Architecture Search for PolSAR Image Classification

TL;DR

This paper introduces a differentiable neural architecture search method tailored for PolSAR image classification, automating CNN design to outperform hand-crafted architectures and incorporating complex-valued networks for enhanced performance.

Contribution

It presents the first application of neural architecture search in PolSAR classification, with a customized differentiable search strategy and complex-valued networks to improve accuracy.

Findings

Achieved better classification performance than hand-crafted CNNs.

Developed a PolSAR-specific search space and improved search strategy.

Demonstrated effectiveness on three benchmark datasets.

Abstract

Convolutional neural networks (CNNs) have shown good performance in polarimetric synthetic aperture radar (PolSAR) image classification due to the automation of feature engineering. Excellent hand-crafted architectures of CNNs incorporated the wisdom of human experts, which is an important reason for CNN's success. However, the design of the architectures is a difficult problem, which needs a lot of professional knowledge as well as computational resources. Moreover, the architecture designed by hand might be suboptimal, because it is only one of thousands of unobserved but objective existed paths. Considering that the success of deep learning is largely due to its automation of the feature engineering process, how to design automatic architecture searching methods to replace the hand-crafted ones is an interesting topic. In this paper, we explore the application of neural architecture search (NAS) in PolSAR area for the first time. Different from the utilization of existing NAS methods, we propose a differentiable architecture search (DAS) method which is customized for PolSAR classification. The proposed DAS is equipped with a PolSAR tailored search space and an improved one-shot search strategy. By DAS, the weights parameters and architecture parameters (corresponds to the hyperparameters but not the topologies) can be optimized by stochastic gradient descent method during the training. The optimized architecture parameters should be transformed into corresponding CNN architecture and re-train to achieve high-precision PolSAR classification. In addition, complex-valued DAS is developed to take into account the characteristics of PolSAR images so as to further improve the performance. Experiments on three PolSAR benchmark datasets show that the CNNs obtained by searching have better classification performance than the hand-crafted ones.