I am not a sailor myself, so I can't give specific questions. But from the content point of view, it is basically the content of advanced mathematics calculus, plus the application in the field of navigation. You can buy an advanced mathematics textbook for navigation majors and have a good look. Spherical triangle, the relationship between sides and angles of spherical triangle, interpolation method, theoretical basis of ship position error and other chapters must be available, otherwise it is not what you want. I hope it helps you ~ ~