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Marine navigation has its own secret language, and let’s face it—half of it sounds like someone making things up after too much grog. You’ve got your ‘dead reckoning,’ which isn’t nearly as ominous as it sounds, and ‘bearing,’ which has nothing to do with polar bears but everything to do with pointing the right way. Don’t even get us started on ‘knots’—why measure speed like you’re tying a shoelace? And then there’s ‘fix (not for your engine) and ‘DR’ (spoiler: it’s not a doctor). If you’re baffled, don’t worry—we’re here to help you decipher this nautical code so you can sound like a pro, not a landlubber who’s lost their compass.
A dimensionless GNSS geometry factor describing how ranging errors are amplified in the receiver-clock estimate. A GNSS receiver solves for its clock offset as well as position because its clock is not synchronised as precisely as the satellites’ atomic clocks. TDOP expresses the geometric contribution to uncertainty in that time solution. Lower TDOP generally indicates…
A dimensionless GNSS geometry factor combining three-dimensional position and receiver-clock uncertainty. GDOP reflects how the relative positions of the satellites used in a solution amplify common ranging errors across latitude, longitude, height and time. It combines position dilution of precision and time dilution of precision, commonly by a root-sum-square relationship. Low GDOP indicates favourable satellite…
An unmanned, self-propelled submersible that carries out a programmed mission without a continuous control link. An AUV uses onboard navigation, sensors, power and control systems to survey or inspect beneath the surface. Typical work includes hydrographic mapping, scientific sampling, pipeline and cable inspection, mine countermeasures and search operations. Unlike a remotely operated vehicle, an AUV…
An expression meaning the straight-line distance between two places, without following roads, channels or terrain. At sea, a straight line on a chart is not automatically a safe or practicable route. Land, shoals, traffic separation schemes, restricted areas, weather and tidal streams may require a longer planned track. Stories that the expression arose from releasing…
The chapter of the SOLAS Convention setting international requirements for safe navigation and navigational services and equipment. It covers matters including navigational warnings, meteorological services, search and rescue, hydrographic services, routeing, reporting, carriage of navigation systems, charts and publications, voyage planning, danger messages and the master’s professional judgement. Unlike many SOLAS chapters, parts of Chapter…
A type-approved shipborne navigation system meeting IMO performance standards for displaying official electronic chart data and supporting route planning and monitoring. With adequate backup arrangements and up-to-date official chart data, ECDIS can satisfy applicable SOLAS chart-carriage requirements. It integrates position and other sensor information with chart objects, safety contours, route checks, alarms and official updates….
The predicted minimum distance between two moving targets if both maintain their present course and speed. Commonly abbreviated to CPA, it is calculated from relative motion and is normally considered with Time to Closest Point of Approach, or TCPA. Radar, AIS and plotting systems can display these values to support assessment of an approaching vessel….
The predicted time remaining until two moving objects reach their calculated closest point of approach if their motions remain unchanged. TCPA is derived with closest point of approach from relative position and velocity, using radar plotting, ARPA, AIS or other tracking. A positive value normally indicates the CPA is ahead in time; a negative value…
Detailed navigation in confined, coastal or harbour waters using a pre-planned sequence of references, limits and actions. A pilotage plan can use visual marks, transits, clearing bearings, soundings, radar ranges, GNSS positions, buoyage, tidal windows, courses, speeds and abort points. It is prepared at a scale and tempo that supports continuous monitoring as hazards and…
If you belive the Earth is flat, you're about to fall of the end...
If you belive the Earth is flat, you're about to fall of the end...
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