At almost the same time as Nathaniel Bowditch published his work in the USA, "The New American Practical Navigator", 1802, almost coincidentally, one J.W.Norie of London published his work in 1803, "Complete Set of Nautical Tables & Epitome of Practical Navigation". Both these publications, updated to match present day navigational techniques, are still being used today. Norie conducted a nautical academy at 157 Leadenhall Street, London. His work was published by the firm of which he later became the principal and surprisingly that firm is still in existence today under the name of Imray, Laurie, Norie & Wilson Ltd. Many British seafarers used, and still use, those tables today. My copy, rather dog-eared, still sits in the bookcase at home.
Angus.
BTW to Maritiem, it helps a great deal if you understand spherical trigonometry, but with the use of Sat. Nav. nowadays I'm not sure how much use is made of the old methods.