If you want to study the compass, there are really no very good books in this field. Books such as Compass Comprehension seen in the market have not been taught, and there is not much knowledge expansion, so it is difficult to estimate by self-study. If you study the four pillars, you can read many books. I suggest you start with the True Solution of Ziping, then read Yuan Hai Ziping, Shen Kao and Ming Manuscript, and finally you can study DiTianmu. Of course, you can also look at Tianyu Jing and Qing nang Jing.