The logbook is a book in which are recorded the state of the wind and weather, the course of the vessel, the distance run daily, latitude, longitude, and any occurrence of importance, whether at sea or at port. Logbooks are all compiled by hand by the captains or an officer.
Logbooks use to have the same standardized format first using handwritten form to create sections, and later in printed pages. In the first and the last pages of the book, the identification data of the ship are mentioned generally: name, type, tonnage, owner, captain, port registry and the unique telegraphic code, validated by the authorities with the note of the exact number of the pages of the book. The logbook had to be compiled once a day and determined the singladura, the day run, from noon to noon. Though navigation or weather information was the core of the logbooks, sometimes the entries also gave information about the ship operation services, daily life, trade routes and the duration of voyage, accidents, illnesses, or deaths. In case of shipwreck, accident or whatever incidence that may occur, the ship logbook was the sine qua non written accepted evidence upon which testimonies had to coincide and legal decisions had to be made.
There is sometimes confusion between Diario de Navegación and another source, the Cuaderno de Bitácola. The latter is the fast register of the daily aspects of navigation, as a draft, that later should be copied in the Diario, which is the formal register of the navigation. Leaving apart legal and administrative consideration, both contain similar information for the researcher. Moreover, as different countries have the same kind of Diario with slight differences, we can use the term logbook to include any variety of this source.