Graph U-Net With Topology-Feature Awareness Pooling for Hyperspectral Image Classification

Nowadays, various graph convolutional networks (GCNs) to process graph-structured data have been proposed for hyperspectral image (HSI) classification. Nevertheless, most GCN-based HSI classification methods emphasize graph node feature aggregation instead of graph pooling, resulting in them being shallow networks and unable to extract deep discriminative features. Besides, to obtain the new graph after the pooling layer, current graph pooling methods used for HSI classification just consider node feature information to select important nodes and directly discard unselected nodes, which could be a subjective process and may cause information loss. To solve this issue, we propose a novel graph U-Net with topology-feature awareness pooling (the so-called TFAP graph U-Net) for HSI classification considering a deep network to extract compelling features and automatically selecting nodes beneficial to classification. More specifically, to establish a more precise pooled graph, the graph's topology structure and node feature information are taken into account, making the node selection process more convincing and objective. Furthermore, to allow that graph nodes preserve more useful graph information, our method aggregates node features from neighboring nodes that may not be selected, which can alleviate the loss of information during the pooling process. Moreover, a cross attention module is employed to filter out irrelevant or noisy features. Finally, we evaluate the proposed method on three public HSI data sets, i.e., Indian Pines, University of Pavia, and University of Houston. The experimental results demonstrate the superiority of the proposed approach compared with other state-of-the-art methods.