What is the main contribution of Guo Shoujing, a scientist in Yuan Dynasty?

Guo Shoujing was a great scientist and astronomer in China at that time. His main contributions were mathematics, astronomy and water conservancy. 1. In astronomy, he compiled 14 kinds of astronomical calendar works, including: Tubu, Licheng, Yi Li Draft, Yi Xiang Law, Notes on the Upper, Middle and Lower Calendars, and the Origin of Calendar Revision, with the number of volumes * * */kl. It took him four years to revise the chronograph calendar and became the most advanced calendar in the world at that time. 2. In terms of science, when Guo Shoujing revised its calendar, it also reformed and invented the simple instrument and twelve instruments used by the Observatory, namely, simple instrument, altimeter, post-meter, mixed planetarium, exquisite instrument, upright instrument, reasoning instrument, scene symbol, peeping instrument, solar eclipse instrument and astrolabe timer. Among them, the simple instrument is to measure the position of celestial bodies, which is an advanced technology in the world at that time. 3. In the field of water conservancy, there are also studies, which have made remarkable achievements and brought far-reaching influence to China. In water conservancy, 129 1 year was responsible for the construction of Tonghui River, a grand canal connecting the Yuan Dynasty and Tongzhou.