Glossary Archive

The maximum angle of heel at which a vessel can recover to an upright position without capsizing. The vanishing angle is a critical concept in naval architecture and marine safety, referring to the point beyond which a vessel loses its ability to right itself and becomes unstable, leading to capsizing. This angle is determined by...

The angular difference between true north and magnetic north, also known as magnetic declination, which affects compass readings. Variation is a crucial concept in marine navigation, as it accounts for the difference between true north (the direction along the Earth's surface towards the geographic North Pole) and magnetic north (the direction a magnetic compass points,...

The International Maritime Signal Flag Victor. Meaning I require assistance.If appended with a Numeral Pennant, Velocity in kilometres per hour.

A measure used in satellite navigation systems, such as GPS, to quantify the impact of satellite geometry on vertical positioning accuracy. It indicates how well-positioned satellites are in relation to one another in the sky. A lower VDOP value indicates better satellite geometry and, therefore, higher accuracy in determining vertical position. A high VDOP value...

A digital nautical chart that represents navigational data using vector graphics, allowing for scalable and interactive mapping of maritime areas. A vector chart is a type of electronic navigational chart (ENC) designed for use in modern marine navigation systems. Unlike raster charts, which are essentially digital images of traditional paper charts, vector charts use mathematical...

The speed at which a vessel is effectively moving towards its intended destination, factoring in both its current speed and the angle of travel relative to the wind or current. Velocity Made Good (VMG) is a crucial concept in sailing and other forms of marine navigation, especially when travelling upwind or downwind. It refers to...

A measure used in satellite navigation systems, such as GPS, to quantify the impact of satellite geometry on vertical positioning accuracy. It indicates how well-positioned satellites are in relation to one another in the sky. A lower VDOP value indicates better satellite geometry and, therefore, higher accuracy in determining vertical position. A high VDOP value...

A range of radio frequencies from 30 MHz to 300 MHz, commonly used in marine communication for short-range, line-of-sight transmissions. Very High Frequency (VHF) is a critical component of maritime communication, providing a reliable and efficient means for vessels to communicate with each other, shore stations, and maritime authorities. The VHF spectrum is divided into...

Any craft designed for transportation on water, including ships, boats, and other waterborne vehicles. A vessel is any structure or craft capable of navigating on water. This includes a wide range of watercraft, from small recreational boats to large commercial ships. The term "vessel" is broad and encompasses various types of watercraft, such as yachts,...

A shore-based system that monitors and manages vessel movements in busy or hazardous waterways to enhance safety, efficiency, and environmental protection.  Vessel Traffic Service (VTS) is an internationally recognised system operated by maritime authorities to regulate and assist vessel movements in congested or high-risk areas such as ports, straits, and busy coastal waters. Using radar,...