HMANet: Hybrid Multiple Attention Network for Semantic Segmentation in Aerial Images.

Semantic segmentation in very-high-resolution (VHR) aerial images is one of the most challenging tasks in remote sensing image understanding. Most of the current approaches are based on deep convolutional neural networks (DCNNs). However, standard convolution with local receptive fields fails in modeling global dependencies. Prior research works have indicated that attention-based methods can capture long-range dependencies and further reconstruct the feature maps for better representation. Nevertheless, limited by the mere perspective of spatial and channel attention and huge computation complexity of self-attention (SA) mechanism, it is unlikely to model the effective semantic interdependencies between each pixel pair of remote sensing data with complex spectra. In this work, we propose a novel attention-based framework named hybrid multiple attention network (HMANet) to adaptively capture global correlations from the perspective of space, channel, and category in a more effective and efficient manner. Concretely, a class augmented attention (CAA) module embedded with a class channel attention (CCA) module can be used to compute category-based correlation and recalibrate the class-level information. In addition, we introduce a simple yet effective region shuffle attention (RSA) module to reduce feature redundant and improve the efficiency of SA mechanism via regionwise representations. Extensive experimental results on the ISPRS Vaihingen, Potsdam benchmark, and iSAID data set demonstrate the effectiveness and efficiency of our HMANet over other state-of-the-art methods.