Extended Operational and Trade Vocabulary

Nautical Science, Navigation and COLREGs glossary (page 3)

The formal navigation and collision-avoidance vocabulary: position accuracy and fix terminology, ARPA target acquisition, abnormal refraction, celestial and terrestrial methods, and the COLREGs rules of the road. Grounds each term in the navigational practice and the collision regulation it serves, the precise counterpart to the deck-seamanship section.

734 defined terms.

Showing 234 on this page (page 3 of 3).

R

RCC (Rescue Coordination Center): Center responsible for SAR within a defined region.
RCDS (Raster Chart Display System): Mode in which ECDIS displays RNCs where ENCs are unavailable.
Real-Time Kinematic (RTK): Centimeter-accurate GNSS used in port automation.
Reciprocal: Bearing 180 degrees from a given bearing.
Reefer (no entry): Cargo term, not navigation.
Refraction (atmospheric): Bending of light through the atmosphere.
Relative bearing: Bearing measured clockwise from ship's head.
Relative motion display: Radar mode in which own ship remains stationary at the center.
Repeater compass: Remote indicator driven by the master gyrocompass.
Restricted visibility: Visibility reduced by fog, mist, rain, or other causes.
Resultant: Vector sum of two or more vectors.
Reverse heading: Heading 180 degrees from the present heading.
Reverse intercept: Intercept when Ho is less than Hc; plotted away from the body.
Rhumb line: Line cutting all meridians at the same angle; straight on a Mercator chart.
Ridge (meteorology): Elongated area of high pressure.
Right ascension: Angular distance measured eastward along the celestial equator from Aries.
Risk of collision: COLREGs Rule 7 concept of imminent danger of contact.
Roll: Rotational motion about the longitudinal axis.
Route monitoring: ECDIS function for monitoring vessel against the planned route.
Route planning: ECDIS function for designing the planned route.
Rule 10 (TSS): Conduct of vessels in or near traffic separation schemes adopted by the IMO.
Rule 11 to 18: Conduct of vessels in sight of one another, including head-on, crossing, overtaking, sailing vessels and responsibilities.
Rule 12: Conduct of sailing vessels.
Rule 13 (Overtaking): Overtaking vessel shall keep out of the way.
Rule 14 (Head-on situation): Each vessel shall alter course to starboard.
Rule 15 (Crossing situation): Vessel which has the other on her starboard side shall keep out of the way.
Rule 16 (Action by give-way vessel): Take early and substantial action.
Rule 17 (Action by stand-on vessel): Maintain course and speed, with permitted action when give-way fails.
Rule 18 (Responsibilities between vessels): Hierarchy of stand-on/give-way among vessel categories.
Rule 19 (Restricted visibility): Conduct of vessels not in sight of one another in restricted visibility.
Rule 20 to 31 (Lights and shapes): Carriage and characteristics of navigation lights and day shapes.
Rule 22 (Visibility of lights): Minimum visibility ranges by vessel length.
Rule 23 (Power-driven vessels underway): Lights to be exhibited.
Rule 24 (Towing and pushing): Lights and shapes for vessels engaged in towing.
Rule 25 (Sailing vessels and vessels under oars): Required lights and shapes.
Rule 26 (Fishing vessels): Lights and shapes when engaged in fishing.
Rule 27 (Not under command and restricted in ability to maneuver): Lights and shapes.
Rule 28 (Vessels constrained by their draught): Optional lights and shapes.
Rule 29 (Pilot vessels): Lights and shapes.
Rule 30 (Anchored vessels and vessels aground): Lights and shapes.
Rule 31 (Seaplanes and WIG craft): Lights and shapes.
Rule 32 to 37 (Sound and light signals): Equipment, maneuvering and warning signals, restricted visibility, attention and distress signals.
Rule 33 (Equipment for sound signals): Required whistle and bell.
Rule 34 (Maneuvering and warning signals): One short, two short, three short and five-or-more short.
Rule 35 (Sound signals in restricted visibility): Required fog signals.
Rule 36 (Signals to attract attention): Use of light or sound.
Rule 37 (Distress signals): Reference to Annex IV.
Rule 5 (lookout): COLREGs requirement for proper lookout.
Rule 6 (Safe speed): Every vessel shall proceed at a safe speed.
Rule 7 (Risk of collision): Use all available means appropriate to determine if risk exists.
Rule 8 (Action to avoid collision): Action shall be positive, made in ample time, and readily apparent.
Rule 9 (Narrow channels): Vessels shall keep as near to the outer limit of the channel on the starboard side as is safe.
Running fix: Position obtained by transferring an earlier LOP using DR.
Russian Federation Hydrographic Service: One of several national chart producers.

S

S-100: IHO Universal Hydrographic Data Model framework.
S-101: IHO product specification for the next-generation Electronic Navigational Chart (ENC).
S-52: IHO standard for ECDIS chart content and display.
S-57: IHO transfer standard for ENCs.
S-63: IHO standard for ENC data protection.
S1: Solar diurnal tidal constituent with period 24 hours.
S2: Principal solar semi-diurnal tidal constituent with period 12 hours.
Safety contour: Depth contour on ECDIS dividing safe from unsafe water for the vessel.
Safety depth: ECDIS parameter highlighting soundings shallower than the value.
Safety zone: Area around an offshore installation entry to which is restricted.
SafetyNET: Inmarsat-C broadcast service for MSI to selected sea or NAVAREAs.
Saffir-Simpson Hurricane Wind Scale: Five-category Atlantic hurricane intensity scale.
Sailing directions: Coastal pilots describing harbors, routes and dangers.
SAR (Search and Rescue): Operations to locate and assist persons in distress.
SART (Search and Rescue Transponder): 9 GHz radar transponder per IMO Res. A.802(19).
Satellite communications (SATCOM): Communications via geostationary or orbiting satellites.
Saturated air: Air at 100 percent relative humidity.
Scale (chart): Ratio of chart distance to corresponding Earth distance.
Scale error: Error introduced by use of inappropriate chart scale.
Scend: Lifting motion of a wave.
Schuler tuning: Property of inertial navigation systems with 84.4-minute period.
Sea Area A1: Within range of at least one VHF coast station with continuous DSC alerting.
Sea Area A2: Within MF DSC coverage outside A1.
Sea Area A3: Within Inmarsat geostationary coverage outside A1 and A2.
Sea Area A4: Polar regions outside A1, A2, A3.
Sea Breeze: Onshore wind driven by differential daytime heating of land and sea.
Sea ice: Frozen sea water of various stages of development.
Sea State Code: WMO scale relating significant wave height to qualitative description.
Secondary port: Port whose tides are predicted by reference to a standard port.
Semidiameter (SD): Half the angular diameter of the Sun or Moon.
Semidiurnal tide: Tide with two roughly equal high and low waters per day.
Sensible horizon: Plane through the observer perpendicular to the plumb line.
Set (current): Direction toward which a current flows.
Sextant: Marine sextant with vernier or micrometer.
Sextant altitude (Hs): Direct reading from the sextant.
SHA (Sidereal Hour Angle): Angle measured westward from Aries to a star.
Shadow pin: Pin on a compass card for taking azimuth of the Sun.
Shallow-water effects: Increase in resistance and squat near the bottom.
Ship Reporting System (SRS): Mandatory or voluntary system for vessels to report position and other data.
Ship Routeing (IMO): IMO publication of adopted routing measures including TSSs.
Side error (sextant): Error when horizon and index mirrors are not parallel.
Sidereal time: Time measured by the rotation of Earth relative to the stars.
Sight (celestial): Observation of a celestial body to obtain a position line.
Sight reduction: Process of converting a celestial observation into a line of position.
Sight Reduction Tables: HO-229 / Pub 229, HO-249 / Pub 249, NP303.
Significant wave height (Hs): Mean of highest one-third wave heights.
Single observer fix: Fix by horizontal sextant angles measured by one observer.
Skywave: Radio wave reflected by the ionosphere.
Slack water: Brief period of no tidal current.
Slot (CPA): Time and range window in which CPA occurs.
Small craft: Vessels generally below SOLAS thresholds.
Smith Island chart: Local reference, not generic.
Snell's law: Law governing refraction of light.
Solar day: Interval between two successive transits of the Sun.
Solar time: Time measured by the Sun.
SOLAS Chapter IV: Radiocommunications, including GMDSS requirements.
SOLAS Chapter V: Safety of Navigation.
SOLAS Regulation V/14: Manning principles; working language on the bridge.
SOLAS Regulation V/19: Carriage requirements for shipborne navigational systems and equipment.
SOLAS Regulation V/22: Navigation bridge visibility.
SOLAS Regulation V/27: Nautical charts and publications kept up to date.
SOLAS Regulation V/34: Safe navigation and voyage planning, referencing IMO Resolution A.893(21).
Sounding: Measured depth.
South Indian Ocean: Tropical cyclone basin south of the equator.
Special mark: IALA yellow mark indicating a special area or feature.
Speed log: Instrument measuring vessel speed through water or over ground.
Speed made good (SMG): Average speed along track over ground.
Speed over ground (SOG): GNSS-derived speed over ground.
Spheroid: Reference ellipsoid for geodetic computations.
Spring Tide: Tide with largest range, near new and full moon.
Squall: Sudden strong wind of short duration.
Squat: Loss of underkeel clearance due to speed in shallow water.
SSAS (Ship Security Alert System): SOLAS XI-2/6 alert system.
Stadimeter: Instrument for measuring distance by height of an object of known size.
Stand-on vessel: COLREGs vessel required to maintain course.
Standard meridian: Meridian used as time reference for a zone.
Standard port: Port for which independent tidal predictions are published.
Star finder: Device such as 2102-D for identifying stars and planets.
Stargazing (twilight): Period when both horizon and stars are visible for sextant sights.
Stationary front: Front with little or no movement.
Steam fog: Fog formed when cold air moves over warmer water (Arctic sea smoke).
Stern light: White light at the stern showing 135 degrees aft.
Storm warning: Warning of wind force 10 or above.
STW (Speed Through Water): Speed measured by log.
Sub-solar point: GP of the Sun.
Subordinate station: Synonym for secondary tide station.
Subsidence (atmosphere): Downward motion of air, associated with high pressure.
Sun's true bearing: Computed azimuth of the Sun used for compass-error checks.
Superior planet: Planet whose orbit lies outside Earth's.
Survey vessel: Hydrographic or geophysical survey ship.
Swell: Long undulating waves from a distant disturbance.
Swing ship: Process of determining deviation by heading the vessel on successive headings while observing the compass.
Synodic month: Period from new Moon to new Moon, 29.53 days.
Synoptic chart: Surface or upper-air weather chart at a specific time.

T

T&P (Temporary and Preliminary) notices: Provisional NTM amendments; included in AIO.
Tabular interpolation: Interpolation method used in HO-229 or NP303.
TCPA (Time to CPA): ARPA-computed time to closest point.
Telegraph (engine): Bridge order communicator to engine room.
Temperature inversion: Layer where temperature rises with height; affects radar propagation.
Tendency (barometric): Three-hour pressure change and character.
Terrestrial fix: Position fix using terrestrial objects, not celestial bodies.
Terrestrial navigation: Navigation by visual and radar reference to land features and aids.
Theodolite: Surveying instrument for horizontal and vertical angles.
Tidal coefficient: French-style indicator of tidal range strength.
Tidal Constituent: Sinusoidal component of the tide such as M2, S2, K1, or O1.
Tidal Datum: Reference plane defined by a phase of the tide such as MLLW.
Tidal diamond: Lettered position on a chart with tabulated tidal-stream data.
Tidal stream: Horizontal water movement due to tides.
Tidal Stream Atlas (NP218 family): UKHO atlases showing hourly tidal streams.
Tide: Periodic vertical rise and fall of water due to gravitational forces of Moon and Sun.
Tide gauge: Instrument recording sea-surface elevation.
Tide tables: Publications giving tidal predictions; see ATT and NP201 to NP204.
Time signal: Radio broadcast of standard time, e.g., from BIPM contributors.
Time zone: Region using a common standard time, generally 15 degrees of longitude wide.
Tonometry (no entry): Not navigation.
Topmark: Shape mounted atop a buoy or beacon for identification.
Total correction (altitude): Combined altitude corrections for a celestial body.
Track: Path actually followed over the ground.
Trade Winds: Persistent easterly winds in the tropics.
Traffic Separation Scheme (TSS): Routeing measure per Ships' Routeing.
Trans-equatorial route: Route crossing the equator.
Transducer: Echo-sounder element converting electrical to acoustic energy.
Transit (range): Line through two charted objects in line, used as a position line.
Transit satellite system: Predecessor of GPS, decommissioned 1996.
Transverse Mercator: Cylindrical projection with cylinder tangent to a meridian.
Trough: Cradle for cylindrical cargo.
TRS (Tropical Revolving Storm): Intense low-pressure system originating in tropical latitudes.
True altitude: Altitude relative to the celestial horizon.
True bearing: Bearing referenced to true north.
True course: Course referenced to true north.
True heading: Heading relative to true north.
True motion display: Radar mode in which own ship and targets move relative to a fixed Earth reference.
True north: Direction toward the geographic north pole.
Turn radius: ECDIS parameter used to model planned course alterations.
Twilight: Civil (Sun 0 to 6 degrees below), Nautical (6 to 12), Astronomical (12 to 18).
Two-bearing fix: Fix from two simultaneous bearings.
Typhoon: Tropical revolving storm of hurricane force in the western North Pacific.

U

UKC (Under Keel Clearance): Vertical distance keel-to-seabed.
UKHO (United Kingdom Hydrographic Office): Producer of Admiralty charts and publications.
Universal Transverse Mercator (UTM): Coordinate system using a series of zones for mapping.
Upper limb: Upper edge of the Sun or Moon as observed in a sextant.
Upwelling: Coastal current rising cold water, relevant in weather routing.
Urgency signal (PAN PAN): Voice signal preceding an urgent message.
UTC (Coordinated Universal Time): International time scale used in navigation and GNSS.

V

Variation (magnetic): Angle between true and magnetic north.
Vector Chart: Layered digital chart used in ECDIS.
Veering (wind): Clockwise change of wind direction in the Northern Hemisphere.
Vertex (great circle): Highest latitude on a great-circle track.
Vertex (TRS): Westernmost point of a TRS track before recurving.
Vertical sextant angle (VSA): Distance found from the sextant angle subtended by an object of known height.
VHF (Very High Frequency): 156 to 174 MHz maritime band including DSC Channel 70.
Visibility: Greatest distance at which an object can be seen.
Visual fix: Position from two or more visual bearings.
Voyage Data Recorder (VDR): SOLAS V/20 black-box equivalent for ships.
Voyage Plan: Required under SOLAS V/34.
VTS (Vessel Traffic Service): Shore-based service to monitor and assist vessel movements.

W

Warm front: Boundary where a warm air mass advances over cooler air.
Warm sector: Region of warm air between warm and cold fronts in a depression.
Watch officer: Synonym for OOW.
Watchkeeping: STCW Chapter VIII deck and engine watchkeeping standards.
Waterline: Line at which the water surface meets the hull.
Wave height: Vertical distance between crest and preceding trough.
Wavelength (sea): Horizontal distance between successive wave crests.
Waypoint: Programmed position on a passage plan.
WGS-84 (World Geodetic System 1984): Reference datum for GPS and most modern charts.
Williamson turn: Man-overboard maneuver returning the ship along her reciprocal track.
Wind Rose: Compass-rose diagram of wind direction frequencies.
Wind sea: Locally wind-generated waves still under wind forcing.
Wind shift: Sudden change of wind direction.
WMO (World Meteorological Organization): Standards for sea/weather observations.
WWNWS (World-Wide Navigational Warning Service): IMO/IHO/WMO MSI dissemination system.

X

X-band radar: 9.4 GHz band marine radar.
XTE / XTD: Cross-track error / distance from planned route.

Y

Yaw: Rotational motion about the vertical axis.
Year (sidereal): 365.2564 days; one orbit of Earth relative to stars.
Year (tropical): 365.2422 days; one cycle of the seasons.

Z

Zenith: Point on celestial sphere directly overhead.
Zenith distance (ZD): 90 degrees minus altitude; angular distance from zenith to body.
Zone description (ZD): Whole number of hours to be added or subtracted from zone time to obtain UTC.
Zone time (ZT): Time kept in a particular time zone.