SD-Net:Spatial dual network for aerial object detection

Compared with the targets in natural images, the aerial targets are often distributed in an arbitrary direction. However, the existing detectors rely on the shared features to identify and locate the targets. This leads to the inconsistency between classification and regression: the classifier needs rotation-invariant features and the regressor needs rotation-sensitive features. To solve the above problems, we propose a Spatial Dual Network (SD-Net) composed of two modules: Spatial Coordinate Attention Module (SCAM) and Polarization Dual Pyramid Module(PDPM). We construct an attention module containing convolution kernels sliding in both horizontal and vertical directions, which enables the attention module to capture channel correlation features and global spatial features in different directions. Then, in the dual pyramid, we separate the features suitable for classification and regression tasks through the polarization function to the classifier and regressor of the network, achieving more refined detection. Extensive experiments show that compared with the existing detectors, our method can achieve higher performance on two remote sensing datasets (i.e. HRSC2016 and DOTA) while maintaining high efficiency.