Li (602-670), an outstanding astronomer, mathematician and Taoist scholar in the Tang Dynasty, was born in Yong (now Fengxiang County, Baoji City, Shaanxi Province). The TuiBei Map written by Li and Yuan Tiangang is famous for its accurate prediction. Li is the first person in the world to grade the wind.

Yuan Tiangang, an astronomer, astrologer and forecaster in the early Tang Dynasty, was born in Chengdu, Yizhou (now Chengdu, Sichuan). The Sui Dynasty was set by salt officials, while the Tang Dynasty was set by volcanoes. He is the author of Six People's Journey, Notes on Five Elements, TuiBei Map, Yuan Tiangang Bone Song, etc. There is a volume of Yi Xuan Jing Yao in Tongzhi Shi Lu. Nine one. Gao Yuxiang, the founder of the contemporary Yiyang School, commented on Yuan Tiangang: "The name is like a bright moon covering a thousand years, and the sound is like Lei Zhen in ancient and modern spring."

It's obviously true.