The On-Orbit Noncloud-Covered Water Region Extraction for Ship Detection Based on Relative Spectral Reflectance

For most of the existing noncloud-covered water region (NCC water region) extraction methods, they are designed for on-ground ship detection. However, these methods could result in low accuracy and expensive computational costs. In this letter, an accurate and fast NCC water region extraction method is proposed for the typical on-orbit ship detection system with limited computing resources available. According to the relative spectral reflectance difference of water, land, and thick cloud, a triple-peak model is first constructed. Next, the parameters of the triple-peak model can be adaptively obtained based on the correlation of the previous adjacent image blocks acquired from the data stream of the panchromatic camera. Subsequently, the accurate NCC water region can be quickly extracted. Moreover, the proposed method is validated using a large amount of raw data captured by panchromatic satellite cameras. The experimental results on a Xilinx-5VFX130t field-programmable gate array imply that the proposed method performs well in the NCC water region extraction with the precision of 99.3% and recall of 99.5%, and it is suitable for on-orbit processing.