Thich nhat hanh (AD 683-727), the common name of Zhang Sui, the method name of Jingxian, was a great Hui Zen master. He was born in Changle, Weizhou (now Nanle County, Puyang City, Henan Province), a monk in the Tang Dynasty, also known as Shaman Party and Alai Pear, and was also called "Gong Yi" by the Tang people. He was a famous astronomer and geomantic master in the Tang Dynasty, and was listed as one of the eight ancestors by the Pravda School.

He is proficient in Sanskrit, familiar with Indian religious documents and knows India's achievements in mathematics and astronomy. His research made full use of the knowledge of trigonometry in India at that time. A group of great grandfathers were Zhang, the minister of Emperor Taizong, a very prominent clan in the early Tang Dynasty. His grandfather, Zhang Dasu, once went to give up his family in Dongtai, a province under the door, and was later demoted to Huai Taishou, whose family fortune fell. His father's name is Zhang Ba, and he is a martial arts county magistrate.

2 1 year-old, due to the death of his parents, he got to know Master Yuquan Hongjing of Tiantai Sect and had the idea of becoming a monk. Therefore, I was shaved as a monk at the entrance of Master Puji in Songshan. I became a monk because I went deep into the "first-line samadhi". Later, he studied Buddhist classics and astronomical mathematics in Songshan and yuquan temple.

In the fifth year of Kaiyuan (7 17), Li Longji, Emperor Xuanzong of the Tang Dynasty, sent someone to take him back to Chang 'an, participated in the translation of the classics of Master Sumitomo, and assisted in the translation of the Great Sunjing. In the ninth year of Kaiyuan (72 1), Emperor Xuanzong of the Tang Dynasty, on the recommendation of Zhang, ordered his party members to preside over the revision of the new calendar "Dayan Calendar". In the same year, together with Liang and Liang, we designed and manufactured astronomical measuring instruments such as ecliptic instrument, armillary sphere and complex moment.

He measured the equatorial coordinates of the stars with the newly-made zodiac navigator, and found that the results were greatly different from those of the Han Dynasty, which was almost a thousand years earlier than the self-viewpoint put forward by the British astronomer Harley in 17 12. In the 12th year of Kaiyuan (723), the delegation presided over a large-scale national astronomical survey, and measured the sun shadow and the height of Polaris at 13 in the north (near the Karahelin site in the southwest of Ulaanbaatar, Mongolia) and the south (central Vietnam). The distance between four locations in Henan Province was also measured.

This is the first large-scale geodetic survey in the history of China. As a result, the traditional saying that "the sun is an inch away" was overthrown. According to the measurement results, the length of the earth meridian can be calculated, which is the first time in the history of science to determine the length of the meridian through observation. In the year when The Great Yan Li was finalized, a group of people died of illness.