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Components of onboard equipment

The electronic equipment installed on board a vessel is the fundamental requirement for the vessel to participate in a VMS programme. This equipment typically consists of some combination of antenna and transceiver, external power source and cabling. Collectively, this equipment is referred to as the VMS Unit or Automatic Location Communicator (other terms have also been used). There may also be external Communications systems - VMS or data input devices, physical Information security - VMS measures, redundant power source, etc.

There are several types of shipboard technologies that serve VMS functions. These technologies all provide common information in a VMS data report: a unique unit identifier, the date and time, and the latitude and longitude. It is important to note that the unique identifier in the data report identifies the shipboard equipment, not the vessel. This distinction relates directly to developing and following best practices in establishing a reliable vessel register, and conducting regular audits and inspections to ensure that shipboard units are, in fact, installed on the proper vessel.

The shipboard unit provides position information in one of two ways. An integrated GPS in the unit may calculate the position directly and include it in the position report, or the satellite system may calculate the unit’s position by measuring Doppler shift in the signal sent from the unit (the change in frequency of the emitted electromagnetic wave when the transmitter and receiver are in motion relative to each other).

The unit’s course (heading) and speed may be calculated directly and transmitted along with the position report, or it may be calculated at the fishery monitoring centre software application, based on the time and distance between position reports.

The basic position-reporting function of this equipment is typically isolated from the vessel operator. Submitting additional data or messages (e.g. entering and sending a catch log, hail report or personal message) usually requires an operator. In addition, the equipment usually has a safety function, allowing the operator to send a distress call through the unit.

The shipboard equipment transmits the basic position reports and ancillary information in several ways. One-way systems send automatic reports at pre-defined intervals, and they may also allow the transmission of ancillary information. Two-way systems also send automatic reports at pre-defined intervals, or the VMS unit may also be “polled” or queried. The option to poll the unit allows the fishery monitoring centre to request information on demand, including an updated position report or status of the equipment, and also to change the reporting interval.

The shipboard equipment most widely used in VMS programmes today includes Argos transmitters, Inmarsat-C and Inmarsat-D+ transceivers, Qualcomm units (EutelTRACS and Boatracs), and Orbcomm systems. Most of this equipment includes an integrated GPS for obtaining positions. The shipboard equipment is designed to be rugged for use in the marine environment, and is manufactured by a variety of companies.

Links to several manufacturers of VMS shipboard units (Note: FAO provides links to vendors as an educational courtesy to readers, and does not endorse or promote any particular manufacturer):

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