Where is the first city in China to participate in the longitude survey of various countries?

This monument was written by Sun Yiqing and now exists in Qingdao Observatory. Calligrapher Profile: Sun Yiqing (1901-kloc-0/990), formerly known as Han Tong, was born in Xiguan Village, Pingdu, Shandong Province. Engage in education until retirement. He used to be a member of Shandong Calligraphers Association, a consultant of Qingdao Calligraphy Research Association, a member of Qingdao Painting Academy and a member of Qingdao Couplet Society. I like calligraphy since I was a child.