Most national shipping authorities and admiralties specify that logbooks are kept to provide a record of events, and to help crews navigate should radio, radar or the GPS fail.
Commercial ships and Naval vessels often keep a "rough log," - or "scrap log," - a preliminary draft of the ship's course, speed, location, and other data, which is then transcribed as the "smooth log," - or "official log" - the final version of the ship's record.