An Ultralightweight Hybrid CNN Based on Redundancy Removal for Hyperspectral Image Classification

Convolutional neural network (CNN)-based hyper- spectral image (HSI) classification models often exhibit high volume and complexity. This not only poses challenges in deploying them on mobile and embedded devices due to storage and power constraints, but also introduces a dilemma between the growing demand for labeled samples and the high cost associated with manual labeling. To address these challenges, we propose an ultralightweight hybrid CNN based on redundancy removal (ULite-R2HCN), specifically designed for HSI classifica- tion in scenarios with limited samples. To reduce computational costs and enhance feature extraction effectiveness, we focus on optimizing the widely used depthwise convolution (DW-Conv) and pointwise convolution (PW-Conv) in the lightweight HSI classification model. For DW-Conv, we design a spatial convo- lution with redundancy removal (R2Spatial-Conv). This involves the design of multiscale 3-D convolution kernels with specific structures instead of 2-D convolution kernels, aiming to reduce redundant convolution kernels and extract multiscale spatial features. Simultaneously, for PW-Conv, we design a spectral convolution with redundancy removal (R2Spectral-Conv). This utilizes a “copy-splicing-grouping” structure to extract spectral features within arbitrary range intervals, effectively reducing redundant spectral extractions and capturing long-range spec- tral relationships. Numerous experiments have shown that the proposed ULite-R2HCN achieves higher classification accuracy with an ultralight volume for a few training samples. In addition, sufficient ablation experiments also verified the advanced perfor- mance of the designed R2Spatial-Conv and R2Spectral-Conv.