A staff member checks a device on a lightship which uses the BeiDou Satellite Navigation System in the Lema Channel on the Pearl River estuary in south China's Guangdong Province, June 20, 2019. The Lema Channel lies to the south of the Hong Kong Island and serves as an important waterway in the eastern part of the Guangdong-Hong Kong-Macao Greater Bay Area. (Xinhua/Tian Jianchuan)