As a mariner, you need reliable products for safe navigation, such as electronic and paper charts and nautical publications. The Hydrographic Service provides official nautical charts, nautical publications and navigation software, as well as Notices to Mariners (NtMs). These are corrections you need to make in order to keep your products up to date.
Every coastal state is obliged to chart its coastal waters. This is a duty under the International Convention for the Safety of Life at Sea (SOLAS Convention).