*Article* **GCBANet: A Global Context Boundary-Aware Network for SAR Ship Instance Segmentation**

**Xiao Ke, Xiaoling Zhang \* and Tianwen Zhang**

School of Information and Communication Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China; xke@std.uestc.edu.cn (X.K.); twzhang@std.uestc.edu.cn (T.Z.) **\***Correspondence:xlzhang@uestc.edu.cn

**Abstract:** Synthetic aperture radar (SAR) is an advanced microwave sensor, which has been widely used in ocean surveillance, and its operation is not affected by light and weather. SAR ship instance segmentation can provide not only the box-level ship location but also the pixel-level ship contour, which plays an important role in ocean surveillance. However, most existing methods are provided with limited box positioning ability, hence hindering further accuracy improvement of instance segmentation. To solve the problem, we propose a global context boundary-aware network (GCBANet) for better SAR ship instance segmentation. Specifically, we propose two novel blocks to guarantee GCBANet's excellent performance, i.e., a global context information modeling block (GCIM-Block) which is used to capture spatial global long-range dependences of ship contextual surroundings, enabling larger receptive fields, and a boundary-aware box prediction block (BABP-Block) which is used to estimate ship boundaries, achieving better cross-scale box prediction. We conduct ablation studies to confirm each block's effectiveness. Ultimately, on two public SSDD and HRSID datasets, GCBANet outperforms the other nine competitive models. On SSDD, it achieves 2.8% higher box average precision (AP) and 3.5% higher mask AP than the existing best model; on HRSID, they are 2.7% and 1.9%, respectively.

**Keywords:** synthetic aperture radar; ship instance segmentation; global context modeling; boundary-aware box prediction
