With modern sight reduction tables, new techniques of working out astronomical observations and the recent changes in the Abridged Nautical Almanac, it has been found that many of the hitherto necessary mathematical tables included in the majority of the nautical tables are now no longer used in the Royal Navy. An analysis in the Royal Navy's navigation school, H.M.S. Dryad, has revealed that only about a third of the tables in each of the three most used books of nautical tables, Burton's, Inman's and Norie's, are used in the Royal Navy.