VDR is the equivalent of a black box in an aircraft. It keeps track of all the details of an accident on the sea, including the time, date, location, speed, and course of the ship. The recorded data can be used in identifying possible safety risks and improve operations.
According to IMO regulations, the standard VDR is required to record an array of data. This includes: date, time, and Coordinated Universal Time, vessel position (latitude and longitude, coordinate reference), velocity and heading audio messages from the bridge (voice messages recorded using one or more microphones placed on the bridge for recording conversations as well as audible alerts) and Very High-Frequency radio Communications (VHF) and radar data (a accurate reproduction of the display on view at the moment of recording), rudder and engine position and watertight door status and accelerations.
The system consists of a concentrator that encodes and processes data streams, sensors that send data to the concentrator and a final recording media (FRM) that can survive accidents and allow for the retrieval of data from voyages. The FRM can be fixed on the vessel, or a floating unit that is connected to EPIRB to allow for early detection in the event of an accident.
The most effective way to ensure the integrity of the vdr system is to make its use an integral component of bridge drills and training of the crew. The saved data can also be used to pinpoint areas that require training and also to improve bridge procedures and operational safety.