CHAPTER5SHORT RANGE AIDS TO NAVIGATIONDEFININGSHORTRANGEAIDSTONAVIGATION500.TermsAndDefinitionses, radiobeacons, racons, Loran C, sound signals, buoysand daybeacons on the navigablewaters of the UnitedStates, its territories,and possessions.Additionally,theTheterm“shortrangeaidstonavigation"encompasseslighted and unlighted beacons, ranges, leading lights,Coast Guard exercises control over privately owned navi-buoys,andtheirassociatedsound signals.Eachshortrangegation aid systems.aidtonavigation,commonlyreferredtoas aNAVAID,fitsA beacon is a stationary,visual navigation aid. Largewithin a system designed to warn themariner of dangerslighthouses and small single-pile structures are both bea-and direct him toward safe water.An aid's function deter-cons.Lighted beacons are called lights;unlighted beaconsmines its color,shape,light characteristic,and sound.Thisare daybeacons.All beacons exhibit a daymark of somechapter explains theU.S.Aids to Navigation System assort.In the case of a lighthouse,the color andtype of strucwell as the international IALA Maritime Buoyage System.ture are the daymarks.On small structures,thesedaymarksTheplacement and maintenanceof marineaids tonavconsisting of colored geometric shapes called dayboardsigation in U.S.watersistheresponsibilityof theUnitedoften have lateral significance.Conversely,the markingsStates Coast Guard.The Coast Guard maintains lighthous-on lighthouses and towers conveyno lateral significance.FIXEDLIGHTSWithfewexceptions,all major lights are operated au-501.MajorAnd MinorLightstomatically.There are also many automatic lights onLights vary from tall, high intensity coastal lights tosmaller structures maintained by the Coast Guard or otherbattery-powered lanterns on single wooden piles.Immov-attendants.Unmanned major lights may have emergencygenerators and automatic monitoring equipment to increaseable, highly visible, and accurately charted, fixed lightsprovide navigators with an excellent source for bearings.the light's reliability.The structures are often distinctively colored to aid in iden-Light structures' appearances vary. Lights in low-lyingtification,SeeFigure50laareas usually are supportedbytall towers,conversely,lightA major light is a high-intensity light exhibited fromstructures on high cliffs may be relatively short.Howevera fixed structure or a marine site.Major lights include pri-its supporttoweris constructed,almostall lights aresimi-mary seacoastlights and secondary lights.Primarylarlygenerated,focused,colored,and characterized.seacoast lights are thosemajor lights established for mak-Some major lights use modern rotating or flashinginglandfallfrom seaand coastwisepassagesfromheadlandlights, but manyolder lights useFresnel lenses.These lens-to headland.Secondary lights are those major lights estab-es consistof intricatelypatterned pieces ofglass inaheavylished at harbor entrances and other locations where highbrassframework.ModernFresnel-typelenses arecastfromintensity and reliability are required.high-gradeplastic:theyaremuchsmallerandlighterthanA minorlight usually displays a light of low to mod-theirglass counterparts.erateintensity.Minor lights are established in harbors,A buoyant beacon provides nearly the positional ac-alongchannels,rivers,andinisolatedlocations.Theyusu-curacyofa light in aplace whereabuoy would normallybeally have numbering,coloring,and light and soundused.SeeFigure5olb.Thebuovantbeaconconsistsofacharacteristicsthatarepartofthelateralsystemofbuoyage.heavy sinker to which a pipe structure is tightly moored. ALighthouses areplacedwhere they will be ofmost usebuoyancy chamber nearthe surface supportsthepipe.Theonprominentheadlands,atharborandportentrances,onlight, radarreflector, and otherdevices are located atop theisolateddangers,or atotherpointswheremarinerscan bestpipe above the surface of the water. The pipe with its buoy-use themtofixtheirposition.Thelighthouse'sprincipaancy chamber tends to remain upright even in severepurpose is to supporta light at a considerableheight aboveweather and heavy currents,providing a smaller watch cir-cle than a buoy.Thebuoyant beacon is most useful alongthe water, thereby increasing its geographic range.Supportequipment is often housednearthetower.narrow ship channels in relatively sheltered water.63
63 CHAPTER 5 SHORT RANGE AIDS TO NAVIGATION DEFINING SHORT RANGE AIDS TO NAVIGATION 500. Terms And Definitions The term “short range aids to navigation” encompasses lighted and unlighted beacons, ranges, leading lights, buoys, and their associated sound signals. Each short range aid to navigation, commonly referred to as a NAVAID, fits within a system designed to warn the mariner of dangers and direct him toward safe water. An aid’s function determines its color, shape, light characteristic, and sound. This chapter explains the U.S. Aids to Navigation System as well as the international IALA Maritime Buoyage System. The placement and maintenance of marine aids to navigation in U.S. waters is the responsibility of the United States Coast Guard. The Coast Guard maintains lighthouses, radiobeacons, racons, Loran C, sound signals, buoys, and daybeacons on the navigable waters of the United States, its territories, and possessions. Additionally, the Coast Guard exercises control over privately owned navigation aid systems. A beacon is a stationary, visual navigation aid. Large lighthouses and small single-pile structures are both beacons. Lighted beacons are called lights; unlighted beacons are daybeacons. All beacons exhibit a daymark of some sort. In the case of a lighthouse, the color and type of structure are the daymarks. On small structures, these daymarks, consisting of colored geometric shapes called dayboards, often have lateral significance. Conversely, the markings on lighthouses and towers convey no lateral significance. FIXED LIGHTS 501. Major And Minor Lights Lights vary from tall, high intensity coastal lights to battery-powered lanterns on single wooden piles. Immovable, highly visible, and accurately charted, fixed lights provide navigators with an excellent source for bearings. The structures are often distinctively colored to aid in identification. See Figure 501a. A major light is a high-intensity light exhibited from a fixed structure or a marine site. Major lights include primary seacoast lights and secondary lights. Primary seacoast lights are those major lights established for making landfall from sea and coastwise passages from headland to headland. Secondary lights are those major lights established at harbor entrances and other locations where high intensity and reliability are required. A minor light usually displays a light of low to moderate intensity. Minor lights are established in harbors, along channels, rivers, and in isolated locations. They usually have numbering, coloring, and light and sound characteristics that are part of the lateral system of buoyage. Lighthouses are placed where they will be of most use: on prominent headlands, at harbor and port entrances, on isolated dangers, or at other points where mariners can best use them to fix their position. The lighthouse’s principal purpose is to support a light at a considerable height above the water, thereby increasing its geographic range. Support equipment is often housed near the tower. With few exceptions, all major lights are operated automatically. There are also many automatic lights on smaller structures maintained by the Coast Guard or other attendants. Unmanned major lights may have emergency generators and automatic monitoring equipment to increase the light’s reliability. Light structures’ appearances vary. Lights in low-lying areas usually are supported by tall towers; conversely, light structures on high cliffs may be relatively short. However its support tower is constructed, almost all lights are similarly generated, focused, colored, and characterized. Some major lights use modern rotating or flashing lights, but many older lights use Fresnel lenses. These lenses consist of intricately patterned pieces of glass in a heavy brass framework. Modern Fresnel-type lenses are cast from high-grade plastic; they are much smaller and lighter than their glass counterparts. A buoyant beacon provides nearly the positional accuracy of a light in a place where a buoy would normally be used. See Figure 501b. The buoyant beacon consists of a heavy sinker to which a pipe structure is tightly moored. A buoyancy chamber near the surface supports the pipe. The light, radar reflector, and other devices are located atop the pipe above the surface of the water. The pipe with its buoyancy chamber tends to remain upright even in severe weather and heavy currents, providing a smaller watch circle than a buoy. The buoyant beacon is most useful along narrow ship channels in relatively sheltered water
64SHORTRANGEAIDS TONAVIGATIONLIGHTFOCALPLANE15PLATFORMWATERLINEBUOYANCYCHAMBERLZAPLABASINKERBOTTOMFigure 501a.Typical offshore light stationFIG25sec"15Figure 501b. Typical design for a buoyant beacon.502.RangeLightslighting.Installation of lightpipes is proceeding on severalrange markers throughout the country.The Coast Guard isRange lights are light pairs that indicate a specific linealsoexperimenting with longrangesodiumlightsforareasrequiring visibility greater than the light pipes can provide.of position when theyarein line.Thehigherrear light isplaced behind the front light. When the mariner sees theTheoutput from a lowpressure sodium light is almostentirely at onewavelength.This allows theuse of an inex-lightsverticallyinline,heisontherangeline.Ifthefrontpensive band-pass filter tomake the light visibleeven duringlightappearsleft ofthe rear light,the observer isto the rightoftherangeline; ifthefront appears to the right oftherearthe daytime.This arrangement eliminates the need for highthe observer is left ofthe rangeline.Range lights are some-intensitylightswiththeirlargepowerrequirementstimes equipped with high intensity lights for daylight use.Range lights are usually white,red, or green.They displayThese are effective for long channels in hazy conditionsvarious characteristics differentiating them from surroundingwhen dayboards might not be seen.The range light struc-lights.tures are usually also equipped with dayboards for ordinaryA directional light is a single light that projects a high in-daytime use.Some smaller ranges,primarily in the Intrac-tensity,special characteristic beam in a given direction. It isoastal Waterwayand other inland waters,have justtheused incases whereatwo-lightrange maynot bepracticabledayboards with no lights.SeeFigure 502.Adirectional sectorlightisadirectional lightthatemitstwoTo enhancethe visibility of range lights, the Coastormorecolored beams.Thebeams haveapreciselyorientedGuard has developed 15-foot long lighted tubes called lightboundarybetweenthem.Anormalapplicationofasectorlightpipes.They are mounted vertically,and the mariner seeswouldshowthreecoloredsections:red.white,andgreenthem as verticalbarsoflightdistinctfrom backgroundThewhitesector would indicatethatthevessel is onthe
64 SHORT RANGE AIDS TO NAVIGATION 502. Range Lights Range lights are light pairs that indicate a specific line of position when they are in line. The higher rear light is placed behind the front light. When the mariner sees the lights vertically in line, he is on the range line. If the front light appears left of the rear light, the observer is to the right of the rangeline; if the front appears to the right of the rear, the observer is left of the rangeline. Range lights are sometimes equipped with high intensity lights for daylight use. These are effective for long channels in hazy conditions when dayboards might not be seen. The range light structures are usually also equipped with dayboards for ordinary daytime use. Some smaller ranges, primarily in the Intracoastal Waterway and other inland waters, have just the dayboards with no lights. See Figure 502. To enhance the visibility of range lights, the Coast Guard has developed 15-foot long lighted tubes called light pipes. They are mounted vertically, and the mariner sees them as vertical bars of light distinct from background lighting. Installation of light pipes is proceeding on several range markers throughout the country. The Coast Guard is also experimenting with long range sodium lights for areas requiring visibility greater than the light pipes can provide. The output from a low pressure sodium light is almost entirely at one wavelength. This allows the use of an inexpensive band-pass filter to make the light visible even during the daytime. This arrangement eliminates the need for high intensity lights with their large power requirements. Range lights are usually white, red, or green. They display various characteristics differentiating them from surrounding lights. A directional light is a single light that projects a high intensity, special characteristic beam in a given direction. It is used in cases where a two-light range may not be practicable. A directional sector light is a directional light that emits two or more colored beams. The beams have a precisely oriented boundary between them. A normal application of a sector light would show three colored sections: red, white, and green. The white sector would indicate that the vessel is on the Figure 501a. Typical offshore light station. Figure 501b. Typical design for a buoyant beacon
65SHORTRANGEAIDS TONAVIGATIONRICHTOFRANE CINEONRANGELINERANCELINE.OFigure 502.Range lightsulations and the applicable Coast Pilot. Certain bridges maychannel centerline;thegreen sector would indicate that thevessel is off the channel centerline inthe direction of deepalso beequipped with sound signals and radar reflectors.water, and the red sector would indicate that the vessel isoff the centerline in thedirection of shoal water.505.Shore LightsShore lights usually have a shore-based power supply503.AeronauticalLightsLights on pilings,such as thosefound in the Intracoastal Wa-Aeronautical lights may be the first lights observed atterway,are batterypowered. Solar panels may be installed tonight when approaching the coast.Those situated near theenhancethelight'spower supply.Thelights consistofa powercoast and visible from sea are listed in the List of Lightssource,aflashertodeterminethecharacteristic,a lampchangThese lights are not listed in the Coast Guard Light List.erto replaceburned-out lamps,andafocusing lensThey usuallyflash alternating white and green.Various types ofrotating lights are in use.They do notAeronautical lights are sequenced geographically inhaveflashers but remain continuouslylitwhile a lens orre-the List of Lights along withmarine navigation lights.How-flector rotatesaround thehorizon,ever, since theyare not maintained formarine navigation,The whole light system is carefully engineered to pro-videthemaximum amount of lighttothemarinerfor thetheyaresubjecttochangesofwhichmaritimeauthoritiesmay not be informed.These changes will be published inleast power use.Speciallydesigned filaments and specialNoticeto Airmen butperhaps not in NoticeToMariners.grades of materials are used in the light to withstand theharshmarineenvironmentThe flasher electronically determines the characteris504.Bridge Lightstic by selectively interrupting the light's power supplyRed, green,and white lights mark bridges across navigaaccordingtothechosencycleble waters ofthe United States. Red lights mark piers and otherThe lamp changer consists of several sockets arrangedparts ofthe bridge.Red lights are also used on drawbridges toaround a central hub. When the circuit is broken by ashowwhenthey arein theclosed position.Green lights markburned-outfilament,a newlamp is rotated into position.Almost all lights have daylight switches whichturn theopendrawbridges and mark the centerlineofnavigable chan-nelsthroughfixedbridges.Thepositionwillvaryaccordingtclightoffatsunriseandonatduskthe type of structure.Navigational lights on bridges in the U.SThe lens for small lights may be one of several types.Thecommon ones in use are omni-directional lenses ofareprescribedbyCoastGuardregulations.Infrequently-used bridges may be unlighted. In foreign155mm,250mm,and300mm.Inaddition,lightsusingpar-waters, the type and method of lighting may be different fromabolic mirrors or focused-beam lenses are used in leadingthose normallyfound inthe United States.Drawbridges whichlights and ranges.The lampfilaments must be carefullymustbeopenedtoallowpassageoperateupon sound and lightaligned with the plane of the lens or mirror to provide themaximum output oflight.The lenssize is chosen accordingsignals given by the vessel and acknowledged by the bridge.Theserequired signals are detailed in the Code ofFederal Regtothetypeofplatform,powersource,andlampcharacteris-
SHORT RANGE AIDS TO NAVIGATION 65 channel centerline; the green sector would indicate that the vessel is off the channel centerline in the direction of deep water; and the red sector would indicate that the vessel is off the centerline in the direction of shoal water. 503. Aeronautical Lights Aeronautical lights may be the first lights observed at night when approaching the coast. Those situated near the coast and visible from sea are listed in the List of Lights. These lights are not listed in the Coast Guard Light List. They usually flash alternating white and green. Aeronautical lights are sequenced geographically in the List of Lights along with marine navigation lights. However, since they are not maintained for marine navigation, they are subject to changes of which maritime authorities may not be informed. These changes will be published in Notice to Airmen but perhaps not in Notice To Mariners. 504. Bridge Lights Red, green, and white lights mark bridges across navigable waters of the United States. Red lights mark piers and other parts of the bridge. Red lights are also used on drawbridges to show when they are in the closed position. Green lights mark open drawbridges and mark the centerline of navigable channels through fixed bridges. The position will vary according to the type of structure. Navigational lights on bridges in the U.S. are prescribed by Coast Guard regulations. Infrequently-used bridges may be unlighted. In foreign waters, the type and method of lighting may be different from those normally found in the United States. Drawbridges which must be opened to allow passage operate upon sound and light signals given by the vessel and acknowledged by the bridge. These required signals are detailed in the Code of Federal Regulations and the applicable Coast Pilot. Certain bridges may also be equipped with sound signals and radar reflectors. 505. Shore Lights Shore lights usually have a shore-based power supply. Lights on pilings, such as those found in the Intracoastal Waterway, are battery powered. Solar panels may be installed to enhance the light’s power supply. The lights consist of a power source, a flasher to determine the characteristic, a lamp changer to replace burned-out lamps, and a focusing lens. Various types of rotating lights are in use. They do not have flashers but remain continuously lit while a lens or reflector rotates around the horizon. The whole light system is carefully engineered to provide the maximum amount of light to the mariner for the least power use. Specially designed filaments and special grades of materials are used in the light to withstand the harsh marine environment. The flasher electronically determines the characteristic by selectively interrupting the light’s power supply according to the chosen cycle. The lamp changer consists of several sockets arranged around a central hub. When the circuit is broken by a burned-out filament, a new lamp is rotated into position. Almost all lights have daylight switches which turn the light off at sunrise and on at dusk. The lens for small lights may be one of several types. The common ones in use are omni-directional lenses of 155mm, 250mm, and 300mm. In addition, lights using parabolic mirrors or focused-beam lenses are used in leading lights and ranges. The lamp filaments must be carefully aligned with the plane of the lens or mirror to provide the maximum output of light. The lens’ size is chosen according to the type of platform, power source, and lamp characterisFigure 502. Range lights
66SHORTRANGEAIDS TONAVIGATIONtics. Additionally,environmental characteristics of thestalled inside the lens to provide the proper characteristic.location are considered.Varioustypes of light-condensingA special heavy 200mm lantern is used in locationspanels, reflex reflectors,or colored sector panels may be in-where ice and breaking water are a hazard.LIGHTCHARACTERISTICS506.CharacteristicsTherefore,thetransition from one colorto another is notabrupt.The colors change through an arc of uncertainty ofA light has distinctive characteristics which distin-2°orgreater, depending onthe optical designof the lightTherefore determining bearings by observing the colonguish itfrom otherlightsor convey specific information.Alight may show a distinctive sequence of light and dark in-change is less accurate than obtaining a bearing with an az-tervals.Additionally,a light may display a distinctive colorimuth circle.or color sequence.In the Light Lists, the dark intervals arereferred to as eclipses.An occulting light is a light totally508.Factors AffectingRangeAnd Characteristicseclipsedatregular intervals,thedurationoflightalways beTheconditionoftheatmospherehasa considerableeffecting greater than the duration of darkness.A flashing lightis a light whichflashesat regular intervals,theduration ofupon a light's range. Sometimes lights are obscured by fog.lightalwaysbeinglessthanthedurationofdarkness.Anhaze,dust, smoke,or precipitation.On theother hand,refrac-isophase light flashes at regular intervals, the duration oftion may cause a light to be seen farther than under ordinarylightbeing equal to the duration ofdarknesscircumstances.AlightoflowintensitywillbeeasilyobscuredLight phase characteristics (Figure 506a and Figurebyunfavorable conditions of theatmosphere.Forthisreason506b)are the distinctive sequences of light and dark inter-the intensity ofa lightshould always be considered when look-vals or sequences in the variations ofthe luminous intensitying for it in thick weather.Haze and distance may reduce theof a light.The light phase characteristics of lights whichapparentduration ofa light'sflash.In some conditions ofthechangecolordonotdifferfromthoseof lightswhichdonotatmosphere,whitelights may have a reddish hue.In clearchange color.Alight showing different colors alternately isweather green lights may have a more whitish hue.described as an alternating light.The alternatingcharacter-Lightsplacedatgreatelevationsaremorefrequentlyisticmaybeused withotherlightphasecharacteristicsobscuredbyclouds.mistandfogthanthosenearsealevelLight-sensitive switches extinguish most lighted navi-In regions where ice conditions prevail, an unattendedlight'slanternpanesmaybecomecoveredwithiceorsnowgation aidsduring daylighthours.However, owingtothevarioussensitivityofthelightswitches,alllightsdonotThis may reduce the light's luminous range and change thecomeon orgooff at the sametime.Mariners should ac-light'sobservedcolor.count for this when identifying aids to navigation duringThedistancefrom a light cannot be estimated by its ap-twilight periods when some lighted aids are on while othersparent brightness.There are too many factors whichcanare not.change the perceived intensity.Also,a powerful, distantlightmaysometimesbeconfusedwithasmaller,closerone507.Light Sectorswith similar characteristics.Every light sighted should becarefullyevaluatedtodetermine if it is the one expectedSectorsof coloredglass orplastic aresometimesThe presence of bright shore lights may make it diffi-placed in thelanterns ofcertain lights to indicatedangerouscult to distinguish navigational lights from backgroundwaters.Lights so equipped showdifferentcolorswhen ob-lighting.Lights mayalso beobscured byvarious shoreob-served from different bearings.A sector changes the colorstructions,natural and man-made. The Coast Guardof a light, but not its characteristic,when viewed from cer-requests mariners to report these cases to the nearest Coasttain directions.For example, a four second flashing whiteGuard station.light havinga red sectorwill appearas a four second flash-A light's loom is seen throughhaze or the reflectioning red light when viewed from within thered sector.from low-lying clouds when the light is beyond its geo-Sectors maybe only a fewdegrees in width or extendgraphic range.Onlythemostpowerful lights cangeneratein a wide arcfrom deepwatertoward shore.Bearings refer-aloom.Theloommaysometimesbesufficientlydefinedtoring to sectors are expressed in degrees true as observedobtain a bearing.If not, an accuratebearing on a light be-fromavessel.yond geographic range may sometimes be obtained byInmostcases,areascovered byred sectors shouldbeascending to a higher level where the light can be seen,andavoided.Thenatureof thedanger canbedetermined fromnoting a star directly over the light.The bearing of the starthe chart. In some cases a narrow sector may mark the bestcan then be obtained from the navigating bridge and thewater across a shoal, or a turningpoint in a channel.bearingtothe lightplotted indirectlyAtshortdistances,someofthebrighterflashinglightsSectors generated by shadow-casting filters do nothave precise boundaries as directional sector lights domayshowafaintcontinuous light,orfaintflashes,between
66 SHORT RANGE AIDS TO NAVIGATION tics. Additionally, environmental characteristics of the location are considered. Various types of light-condensing panels, reflex reflectors, or colored sector panels may be installed inside the lens to provide the proper characteristic. A special heavy 200mm lantern is used in locations where ice and breaking water are a hazard. LIGHT CHARACTERISTICS 506. Characteristics A light has distinctive characteristics which distinguish it from other lights or convey specific information. A light may show a distinctive sequence of light and dark intervals. Additionally, a light may display a distinctive color or color sequence. In the Light Lists, the dark intervals are referred to as eclipses. An occulting light is a light totally eclipsed at regular intervals, the duration of light always being greater than the duration of darkness. A flashing light is a light which flashes at regular intervals, the duration of light always being less than the duration of darkness. An isophase light flashes at regular intervals, the duration of light being equal to the duration of darkness. Light phase characteristics (Figure 506a and Figure 506b) are the distinctive sequences of light and dark intervals or sequences in the variations of the luminous intensity of a light. The light phase characteristics of lights which change color do not differ from those of lights which do not change color. A light showing different colors alternately is described as an alternating light. The alternating characteristic may be used with other light phase characteristics. Light-sensitive switches extinguish most lighted navigation aids during daylight hours. However, owing to the various sensitivity of the light switches, all lights do not come on or go off at the same time. Mariners should account for this when identifying aids to navigation during twilight periods when some lighted aids are on while others are not. 507. Light Sectors Sectors of colored glass or plastic are sometimes placed in the lanterns of certain lights to indicate dangerous waters. Lights so equipped show different colors when observed from different bearings. A sector changes the color of a light, but not its characteristic, when viewed from certain directions. For example, a four second flashing white light having a red sector will appear as a four second flashing red light when viewed from within the red sector. Sectors may be only a few degrees in width or extend in a wide arc from deep water toward shore. Bearings referring to sectors are expressed in degrees true as observed from a vessel. In most cases, areas covered by red sectors should be avoided. The nature of the danger can be determined from the chart. In some cases a narrow sector may mark the best water across a shoal, or a turning point in a channel. Sectors generated by shadow-casting filters do not have precise boundaries as directional sector lights do. Therefore, the transition from one color to another is not abrupt. The colors change through an arc of uncertainty of 2° or greater, depending on the optical design of the light. Therefore determining bearings by observing the color change is less accurate than obtaining a bearing with an azimuth circle. 508. Factors Affecting Range And Characteristics The condition of the atmosphere has a considerable effect upon a light’s range. Sometimes lights are obscured by fog, haze, dust, smoke, or precipitation. On the other hand, refraction may cause a light to be seen farther than under ordinary circumstances. A light of low intensity will be easily obscured by unfavorable conditions of the atmosphere. For this reason, the intensity of a light should always be considered when looking for it in thick weather. Haze and distance may reduce the apparent duration of a light’s flash. In some conditions of the atmosphere, white lights may have a reddish hue. In clear weather green lights may have a more whitish hue. Lights placed at great elevations are more frequently obscured by clouds, mist, and fog than those near sea level. In regions where ice conditions prevail, an unattended light’s lantern panes may become covered with ice or snow This may reduce the light’s luminous range and change the light’s observed color. The distance from a light cannot be estimated by its apparent brightness. There are too many factors which can change the perceived intensity. Also, a powerful, distant light may sometimes be confused with a smaller, closer one with similar characteristics. Every light sighted should be carefully evaluated to determine if it is the one expected. The presence of bright shore lights may make it difficult to distinguish navigational lights from background lighting. Lights may also be obscured by various shore obstructions, natural and man-made. The Coast Guard requests mariners to report these cases to the nearest Coast Guard station. A light’s loom is seen through haze or the reflection from low-lying clouds when the light is beyond its geographic range. Only the most powerful lights can generate a loom. The loom may sometimes be sufficiently defined to obtain a bearing. If not, an accurate bearing on a light beyond geographic range may sometimes be obtained by ascending to a higher level where the light can be seen, and noting a star directly over the light. The bearing of the star can then be obtained from the navigating bridge and the bearing to the light plotted indirectly. At short distances, some of the brighter flashing lights may show a faint continuous light, or faint flashes, between
67SHORTRANGEAIDSTONAVIGATIONTypeDoscrintionAtrevisticnmtastrationF1.FIXEDAligntshowing continuouslyendsteadily2OCCULTINGAightin wtichthetotalduraticn of light inaperiod is longer than thetotalduration ofdarkness and the intervals otdarknese (ecipses)are usually cfequelduraticn.O2.1Single-occulting.An occulting light in which an eclipse is regularly repeated.pertod2.2Group-occulting.Oc(2)Ancculingghtinwhichgroupofcipses,specifiedinnubssgulaperiodrepeated.Oc(2+1)2.3Compositegroup-occulting.Alight,sinlar to sgroup-occutting Tight,except thaf sucoessivegroups in aperiedperiod have different numbers of eclipses.3.ISOPHASE.IsoAlight in wtich all durations of ight and darkress are equalperod4.FLASHINGA ight in which the total duration of light in a period is shorter than the totalduraticn otdariness and the sppesrancesoflight (lashes) areususily ofequalduration.FI4.1Single-flashing.88Afiashing light in which a fiash is regularly repeatec (frequency notexceeding 30perios,fashes per minute)===THISFIGUREHASTOBEREPAIRED!!==Figure 506a.Light phase characteristics.===-.=
SHORT RANGE AIDS TO NAVIGATION 67 Figure 506a. Light phase characteristics. = = = = = = THIS FIGURE HAS TO BE REPAIRED!! = = = = = =
68SHORTRANGEAIDS TONAVIGATIONTypeDesariptionustralxanAttrevation4.2Group-flashing.FI (2)日Aflashinglightinwhichagroupof flashes,specified in number,isregularly,petod,repeated.4.3 Compositegroup-flashingAlightsimilarto agroupflashing lightexceptthat successivegroups intheperiodFI(2+perfod.havedifferentnumbersofflashes.5.QUICK.A light in which flashes are produced at a raleof 60 fiashes perminute5.1ContinuousquickaAquick light in which a flash is regularly repeated.IQ5.2InterruptedquickA quick light in which the sequence of flashes is interrupted by regularly repeatededipsesofconstantandlongduration.6.MORSECODEMo(AAlight in whichappearances of lightoftwoclearlydifferentdurations (dotsandperioddashes) are grouped to represent a characteror characters in the Morse codeFFI7.FIXEDANDFLASHING.Alight in which a fixed light is combined with a flashing light of higherluminousperiod,intensity.AIRM8.ALTERNATINGAlightshowingdifferentcolorsallemalelyperioe,Figure506b.Lightphasecharacteristics
68 SHORT RANGE AIDS TO NAVIGATION Figure 506b. Light phase characteristics
69SHORTRANGEAIDS TONAVIGATIONregular flashes. This is due to reflections of a rotating lensalternating flashing white and red (F W AI WR).This is be-on panes of glass in the lighthousecause for a given candlepower, white is the most visibleIf a light is not sighted within a reasonable time aftercolor,green less so,and red leastofthethree.Thisfactalsoprediction,adangerous situation may exist.Conversely,theaccounts for the differentrangesgiven in the Light Lists forlightmay simply be obscured or extinguished.The ship'ssome multi-color sector lights.Thesame lamphas differentposition should immediatelybefixedby othermeanstode-ranges according to the color imparted by the sector glasstermine any possibility of danger.A light may be extinguished due to weather,batteryThe apparent characteristic of a complex light mayfailure,vandalism,or other causes.In the case of unattend-changewith thedistance of the observer.For example,aed lights,this condition might not beimmediatelylight with a characteristic of fixed white and alternatingcorrected.Themariner should report this condition to theflashing whiteand redmayinitially showas a simpleflash-nearest Coast Guard station.During periods of armed con-ing white light. As the vessel draws nearer, the red flashflict, certain lights may be deliberately extinguishedwill become visible and the characteristic willapparentlybewithout notice.alternating flashing white and red. Later, the fainter fixedOffshorelight stations should alwaysbeleft well offwhite light will be seen between the flashes and the truecharacteristicofthelightfinallyrecognizedasfixedwhite,the course whenever searoom permits.BUOYS509.Definitions And TypesBuoys arefloating aids to navigation.Theymarkchannels, indicate shoals and obstructions,and warn the marinerof dangers.Buoys are used where fixed aids would be un-economicalorimpracticalduetothedepthofwater.Bytheir color,shape,topmark,number,and light characteris-tics,buoys indicatetothemariner howtoavoid hazards andstay in safe water.The federal buoyage system in the U.S.ismaintainedbytheCoastGuard.Therearemanydifferent sizes and types of buoys de-signedto meeta widerangeofenvironmental conditionsand user requirements.The size ofabuoy is determined primarily by its location.In general, the smallest buoy whichwill stand up to local weather and current conditions ischosen.There are five types of buoys maintained by the CoastGuard. They are:1.Lateral marks.Figure 509.Buoy showing counterweight.2.Isolated danger marks.3.Safewatermarks.15to20feethigh.The designed nominal visual range is3.84.Specialmarks.miles, and the radar range 4 miles. Actual conditions will5.Information/regulatorymarks.cause these range figures to vary considerably.The smallest buoys are designed for protected waterTheseconform ingeneral tothe specifications of theSomearemadeof plastic and weighonly40pounds.SpeInternational Association of Lighthouse Authoritiescially designed buoys are used for fast current, ice, and(IALA) buoyage system.otherenvironmental conditions.Alighted buoyis a floating hull with atower on whichAvariety of special purpose buoys are owned by othera light is mounted.Batteries for the light are in watertightgovermmental organizations.Examplesof theseorganiza-pockets in the buoyhull or in watertight boxesmounted ontions include the Panama Canal Commission,the Stthe buoy hull.To keep the buoy in an upright position, aLawrenceSeawayDevelopmentCorporation,NOAA,andcounterweight is attached to the hull below the water sur-the Department of Defense.These buoys are usually navi-face.A radar reflector is built into the buoy tower.gational marks or data collection buoys with traditionalThelargest ofthetypicalU.S.CoastGuard buoys canround, boat-shaped, or discus-shaped hulls.bemoored in upto190feetofwater,limited by the weightof chain the hull can support. The focal plane ofthe light isA special class of buoy,theOceanDataAcquisition
SHORT RANGE AIDS TO NAVIGATION 69 regular flashes. This is due to reflections of a rotating lens on panes of glass in the lighthouse. If a light is not sighted within a reasonable time after prediction, a dangerous situation may exist. Conversely, the light may simply be obscured or extinguished. The ship’s position should immediately be fixed by other means to determine any possibility of danger. The apparent characteristic of a complex light may change with the distance of the observer. For example, a light with a characteristic of fixed white and alternating flashing white and red may initially show as a simple flashing white light. As the vessel draws nearer, the red flash will become visible and the characteristic will apparently be alternating flashing white and red. Later, the fainter fixed white light will be seen between the flashes and the true characteristic of the light finally recognized as fixed white, alternating flashing white and red (F W Al W R). This is because for a given candlepower, white is the most visible color, green less so, and red least of the three. This fact also accounts for the different ranges given in the Light Lists for some multi-color sector lights. The same lamp has different ranges according to the color imparted by the sector glass. A light may be extinguished due to weather, battery failure, vandalism, or other causes. In the case of unattended lights, this condition might not be immediately corrected. The mariner should report this condition to the nearest Coast Guard station. During periods of armed conflict, certain lights may be deliberately extinguished without notice. Offshore light stations should always be left well off the course whenever searoom permits. BUOYS 509. Definitions And Types Buoys are floating aids to navigation. They mark channels, indicate shoals and obstructions, and warn the mariner of dangers. Buoys are used where fixed aids would be uneconomical or impractical due to the depth of water. By their color, shape, topmark, number, and light characteristics, buoys indicate to the mariner how to avoid hazards and stay in safe water. The federal buoyage system in the U.S. is maintained by the Coast Guard. There are many different sizes and types of buoys designed to meet a wide range of environmental conditions and user requirements. The size of a buoy is determined primarily by its location. In general, the smallest buoy which will stand up to local weather and current conditions is chosen. There are five types of buoys maintained by the Coast Guard. They are: 1. Lateral marks. 2. Isolated danger marks. 3. Safe water marks. 4. Special marks. 5. Information/regulatory marks. These conform in general to the specifications of the International Association of Lighthouse Authorities (IALA) buoyage system. A lighted buoy is a floating hull with a tower on which a light is mounted. Batteries for the light are in watertight pockets in the buoy hull or in watertight boxes mounted on the buoy hull. To keep the buoy in an upright position, a counterweight is attached to the hull below the water surface. A radar reflector is built into the buoy tower. The largest of the typical U.S. Coast Guard buoys can be moored in up to 190 feet of water, limited by the weight of chain the hull can support. The focal plane of the light is 15 to 20 feet high. The designed nominal visual range is 3.8 miles, and the radar range 4 miles. Actual conditions will cause these range figures to vary considerably. The smallest buoys are designed for protected water. Some are made of plastic and weigh only 40 pounds. Specially designed buoys are used for fast current, ice, and other environmental conditions. A variety of special purpose buoys are owned by other governmental organizations. Examples of these organizations include the Panama Canal Commission, the St. Lawrence Seaway Development Corporation, NOAA, and the Department of Defense. These buoys are usually navigational marks or data collection buoys with traditional round, boat-shaped, or discus-shaped hulls. A special class of buoy, the Ocean Data Acquisition Figure 509. Buoy showing counterweight
70SHORTRANGEAIDSTONAVIGATIONSystem (ODAS) buoy,is moored or floats free in offshoreUnder normal conditions, the lenses used on buoys arewaters.Positions arepromulgated throughradio warnings.155mm in diameter at the base.200 mm lenses areusedThesebuoys aregenerally not largeenoughto causedam-where breaking waves or swells call forthe largerlensage in a collision, but should be given a wide berthThey are colored according to the charted characteristic ofregardless,asanyloss wouldalmost certainlyresult inthethe buoy,As in shore lights,thelamp must be carefullyfo-interruption of valuable scientific experiments.They arecusedsothatthefilamentisdirectlyinlinewiththefocalgenerally bright orange or yellow in color, with verticalplane of the lens.This ensures that the majority of the lightstripes on moored buoys and horizontal bandsonfree-float-produced isfocused in a360°horizontal fan beamAbuoyingones,andhaveastrobelightfornightvisibility.lighthasarelativelynarrowverticalprofile.Becausethebuoyrocks inthesea,thefocal planemayonlybevisibleEvenin clearweather,thedanger of collisionwithabuoy exists.If struck head-on,a large buoy can inflict se-for fractions of a second at great ranges.Arealistic rangefor sighting buoylights is 4-6miles in good visibilityveredamageto a large ship;itcan sink a smaller oneReduced visibility orheavy background lighting can con-tribute totheproblem.TheCoastGuardsometimes511.SoundSignalsOnBuoysreceivesreportsofbuovsmissingfromstationthatwereac-tuallyrun down and sunk.Tugboats and towboats towing orLighted sound buoys have the same general configura-pushing barges are particularly dangerousto buoys becausetion as lighted buoys but are equipped with either a bell,of poor over-the-bow visibility when pushing or yawinggong,whistle, or horn.Bells and gongs are soundedby tap-duringtowing.Theprofessional marinermustreportanypers hangingfromthetower that swing as thebuoys roll incollision with a buoy to the nearest Coast Guard unit.Fail-thesea.Bellbuoys produceonlyone tone;gongbuoys pro-ure to do so may cause the next vessel to miss the channelduce several tones.The tone-producingdevice is mountedor hit the obstruction marked by the buoy, it can also leadbetweenthelegsofthepillarortower.tofines and legal liabilityWhistlebuoys makea loud moaning sound caused byRoutineon-stationbuoy maintenance consists of in-the rising and falling motions of the buoy in the sea.Aspecting themooring,cleaning thehulland superstructure,soundbuoyequipped with anelectronic horn will producereplacing thebatteries,flasher,and lamps,checking wiringa pure tone at regular intervals regardless of the sea stateand venting systems,and verifying thebuoy's exactposi-Unlighted sound buoys havethe samegeneral appearancetion.Everyfewyears,eachbuoyisreplaced bya similar aidas lighted buoys, but their underwater shape is designed toand returned to a Coast Guard maintenance facility formakethemlivelyinallseastates.completerefurbishmentThe placement of a buoydepends on its purposeand its512.BuoyMooringspositiononthechart.Mostbuoys areplaced onchartedposi-tion as accurately as conditions allow.However, if a buoy'sBuoys require moorings tohold them inposition.Typ-purpose is to mark a shoal and the shoal isfound to be in a dif-icallythemooringconsistsof chain anda largeconcreteferentposition thanthechartshows,thebuoywill beplacedtoproperly mark the shoal, and not on its charted position.510. Lights On BuoysBuoy light systems consist ofa battery pack,a flasherwhichdeterminesthecharacteristic,a lampchangerwhichautomaticallyreplacesburned-outbulbs,alenstofocusthelight,and ahousing which supports thelens and protectsthe electrical equipment.The batteries consist of 12-volt lead/acid type batter-ies electricallyconnectedtoprovidesufficientpowertoruntheproperflashcharacteristic and lampsize.Thesebatterypacks are contained in pockets in the buoy hull,accessiblethroughwater-tightboltedhatchesorexternallymountedboxes.Careful calculations based on light characteristicsdeterminehowmuchbatterypowerto install.Theflasher determines the characteristic of the lamp.It is installed in the housing supporting thelens.Thelampchanger consists of several socketsarrangedaroundacentral hub.AnewlamprotatesintopositioniftheFigure512.Asinker used toanchor abuoyactiveoneburnsout
70 SHORT RANGE AIDS TO NAVIGATION System (ODAS) buoy, is moored or floats free in offshore waters. Positions are promulgated through radio warnings. These buoys are generally not large enough to cause damage in a collision, but should be given a wide berth regardless, as any loss would almost certainly result in the interruption of valuable scientific experiments. They are generally bright orange or yellow in color, with vertical stripes on moored buoys and horizontal bands on free-floating ones, and have a strobe light for night visibility. Even in clear weather, the danger of collision with a buoy exists. If struck head-on, a large buoy can inflict severe damage to a large ship; it can sink a smaller one. Reduced visibility or heavy background lighting can contribute to the problem. The Coast Guard sometimes receives reports of buoys missing from station that were actually run down and sunk. Tugboats and towboats towing or pushing barges are particularly dangerous to buoys because of poor over-the-bow visibility when pushing or yawing during towing. The professional mariner must report any collision with a buoy to the nearest Coast Guard unit. Failure to do so may cause the next vessel to miss the channel or hit the obstruction marked by the buoy; it can also lead to fines and legal liability. Routine on-station buoy maintenance consists of inspecting the mooring, cleaning the hull and superstructure, replacing the batteries, flasher, and lamps, checking wiring and venting systems, and verifying the buoy’s exact position. Every few years, each buoy is replaced by a similar aid and returned to a Coast Guard maintenance facility for complete refurbishment. The placement of a buoy depends on its purpose and its position on the chart. Most buoys are placed on charted position as accurately as conditions allow. However, if a buoy’s purpose is to mark a shoal and the shoal is found to be in a different position than the chart shows, the buoy will be placed to properly mark the shoal, and not on its charted position. 510. Lights On Buoys Buoy light systems consist of a battery pack, a flasher which determines the characteristic, a lamp changer which automatically replaces burned-out bulbs, a lens to focus the light, and a housing which supports the lens and protects the electrical equipment. The batteries consist of 12-volt lead/acid type batteries electrically connected to provide sufficient power to run the proper flash characteristic and lamp size. These battery packs are contained in pockets in the buoy hull, accessible through water-tight bolted hatches or externally mounted boxes. Careful calculations based on light characteristics determine how much battery power to install. The flasher determines the characteristic of the lamp. It is installed in the housing supporting the lens. The lamp changer consists of several sockets arranged around a central hub. A new lamp rotates into position if the active one burns out. Under normal conditions, the lenses used on buoys are 155mm in diameter at the base. 200 mm lenses are used where breaking waves or swells call for the larger lens. They are colored according to the charted characteristic of the buoy. As in shore lights, the lamp must be carefully focused so that the filament is directly in line with the focal plane of the lens. This ensures that the majority of the light produced is focused in a 360° horizontal fan beam A buoy light has a relatively narrow vertical profile. Because the buoy rocks in the sea, the focal plane may only be visible for fractions of a second at great ranges. A realistic range for sighting buoy lights is 4-6 miles in good visibility. 511. Sound Signals On Buoys Lighted sound buoys have the same general configuration as lighted buoys but are equipped with either a bell, gong, whistle, or horn. Bells and gongs are sounded by tappers hanging from the tower that swing as the buoys roll in the sea. Bell buoys produce only one tone; gong buoys produce several tones. The tone-producing device is mounted between the legs of the pillar or tower. Whistle buoys make a loud moaning sound caused by the rising and falling motions of the buoy in the sea. A sound buoy equipped with an electronic horn will produce a pure tone at regular intervals regardless of the sea state. Unlighted sound buoys have the same general appearance as lighted buoys, but their underwater shape is designed to make them lively in all sea states. 512. Buoy Moorings Buoys require moorings to hold them in position. Typically the mooring consists of chain and a large concrete Figure 512. A sinker used to anchor a buoy
71SHORTRANGEAIDSTONAVIGATIONorcast iron sinker.SeeFigure512.Because buoys are sub-36 feet abovethe water.Emergencylights automaticallyjectedtowaves,wind,andtides,themooringsmustbeenergize if the main light is extinguished.These buoys maydeployed with chain lengthsmuch greaterthanthewateralso have a radiobeacon and sound signals.Their conditiondepth.Thescopeof chainwill normallybeabout3timesismonitoredbyradiofromshore.the water depth.The lengthof themooringchaindefines awatch circle within which the buoy can be expected to514.WreckBuoysswing.It isforthis reason thatthecharted buoysymbol hasa“position approximate"circle to indicate its charted posiA wreck buoy usually cannot be placed directly overtion, whereas a light position is shown bya dot at the exactthe wreck it is intended to mark because the buoy tenderlocation.Actualwatchcirclesdonotnecessarilycoincidemay not want to pass over a shallow wreck or risk foulingwith the“position approximate"circles which representthe buoy mooring. For this reason, a wreck buoy is usuallythem.placed as closelyas possible ontheseaward orchannelwardOver several years, the chain gradually wears out andside of a wreck.In some situations, two buoys maybe usedmust be replaced with new.The worn chain is often casttomark thewreck,onelyingoff each end.Thewreckmayintotheconcreteofnewsinkers.lie directlybetween themor inshore ofa line between them,depending on the local situation.The Local NoticeTo Mar-513.LargeNavigationalBuoysiners should be consulted concerning details of theplacementof wreck buoys on individual wrecks.Often itLarge navigational buoys are moored in open waterwill also give particulars of the wreck and what activitiesatapproachestomajor seacoastports.These40-footdiam-eter buoys (Figure 513)show lights fromheights of aboutmay be in progress to clear itGUARDCOASTFigure513.Largenavigational buoy
SHORT RANGE AIDS TO NAVIGATION 71 or cast iron sinker. See Figure 512. Because buoys are subjected to waves, wind, and tides, the moorings must be deployed with chain lengths much greater than the water depth. The scope of chain will normally be about 3 times the water depth. The length of the mooring chain defines a watch circle within which the buoy can be expected to swing. It is for this reason that the charted buoy symbol has a “position approximate” circle to indicate its charted position, whereas a light position is shown by a dot at the exact location. Actual watch circles do not necessarily coincide with the “position approximate” circles which represent them. Over several years, the chain gradually wears out and must be replaced with new. The worn chain is often cast into the concrete of new sinkers. 513. Large Navigational Buoys Large navigational buoys are moored in open water at approaches to major seacoast ports. These 40-foot diameter buoys (Figure 513) show lights from heights of about 36 feet above the water. Emergency lights automatically energize if the main light is extinguished. These buoys may also have a radiobeacon and sound signals. Their condition is monitored by radio from shore. 514. Wreck Buoys A wreck buoy usually cannot be placed directly over the wreck it is intended to mark because the buoy tender may not want to pass over a shallow wreck or risk fouling the buoy mooring. For this reason, a wreck buoy is usually placed as closely as possible on the seaward or channelward side of a wreck. In some situations, two buoys may be used to mark the wreck, one lying off each end. The wreck may lie directly between them or inshore of a line between them, depending on the local situation. The Local Notice To Mariners should be consulted concerning details of the placement of wreck buoys on individual wrecks. Often it will also give particulars of the wreck and what activities may be in progress to clear it. Figure 513. Large navigational buoy
72SHORTRANGEAIDSTONAVIGATIONThecharted position of a wreckbuoy will usuallybeproximate position of the sinker which secures the buoy tooffset from the actual geographic position so that the wreckthe seabed. The approximate position is used because ofandbuoysvmbolsdonotcoincide.Onlyonthelargestscalepractical limitations in placing and keeping buoys and theirchartwill theactual and charted positions ofboth wreckandsinkers inprecise geographical locations.These limitationsbuoy bethe same.Where theymight overlap, it is the wreckinclude prevailing atmospheric and sea conditions,thesymbol which occupies the exact charted position and theslope and type of material making up the seabed, the scopebuoysymbolwhichisoffset.of themooring chain, and thefactthat thepositions oftheWreckbuoys arerequired tobeplacedbytheownerofbuovsandthesinkersarenotundercontinuoussurveil-thewreckbuttheymaybeplacedbytheCoastGuardifthelance.Thepositionofthebuoyshiftsaroundtheareashownowner isunableto comply withthis requirement.Ingener-bythechartsymbolduetotheforcesofwind and currental,privatelyplaced aids are not as reliableas Coast GuardA buoy may not be in its charted position becauseofaids.changes in the feature itmarks.For example,a buoy meantSunkenwrecks are sometimes movedawayfromtheirto mark a shoal whose boundaries are shifting might fre-buoysbystorms,currents,freshets,orothercauses.Justasquentlybe moved to markthe shoal accurately.A Localshoalsmayshiftawayfromthebuoysplacedtomarkthem,NoticeTo Mariners will report the change,and a NoticeTowrecksmayshiftawayfromwreckbuoys.Mariners chart correction may also be written.In somesmall channels which change often,buoys arenot charted515.Fallibility Of Buoyseven when considered permanent, local knowledge is ad-vised in such areas.Buoys cannotberelied on tomaintain their charted po-For these reasons,amarinermust not rely completelysitions consistently.They are subject to a variety ofhazardsupon theposition or operation ofbuoys,but should navigateincluding severe weather, collision, mooring casualties, andusing bearings of charted features, structures, and aids toelectrical failure.Reportanydiscrepancynoted inabuoytonavigationon shore.Further,avesselattemptingtopasstootheU.S.Coast Guardclose aboard a buoy risks a collision with the buoy or theThe buoy symbol shown on charts indicates the ap-obstruction it marks.BUOYAGESYSTEMS516.LateralAndCardinalSystemsmercebetween countries,theneedfor a uniform systemofbuoyage became apparent.There aretwo major types of buoyage systems:theIn 1889,an International MarineConferenceheld inlateral system and the cardinal system.The lateral sys-Washington,D.C.,recommendedthatinthelateral system,tem is best suited for well-defined channels. Thestarboard hand buoys be painted red and port hand buoysblack.Unfortunately,when lights for buoys were intro-description of each buoy indicates thedirection of dangerrelativetothecoursewhichisnormallyfollowed.Inprin-duced someyears later,some European countriesplacedciple,the positions of marks in the lateral system arered lights ontheblackport hand buoystoconform withthedetermined by the general direction taken by the marinerred lights marking theport sideof harbor entrances,whilewhen approaching portfrom seaward.These positionsin North America red lights wereplaced on red starboardhandbuoys.In1936,aLeagueofNationssubcommitteemayalsobedeterminedwithreferencetothemainstreamof flood current.TheUnited States Aids toNavigationrecommended a coloring system oppositeto the1889System is a lateral system.proposal.The cardinal system is best suited for coasts with nu-The International Association of Lighthouse Au-thorities (IALA) is a non-governmental organizationmerous isolated rocks,shoals,and islands,and for dangersin the open sea.The characteristic of each buoy indicateswhichconsistsofrepresentativesoftheworldwidecommu-the approximate truebearing of the danger it marks.Thus,nity ofaidsto navigation services to promoteinformationan eastern quadrant buoy marks a danger which lies to theexchangeandrecommend improvementsbased on newwestofthebuoy.Thefollowingpages diagram thecardinaltechnologies.In1980,withthe assistanceof IMOandtheIHO,the lighthouse authorities from 50 countries and rep-and lateral buoyage systems as found outside the UnitedStates.resentativesof9internationalorganizationsconcernedwithaids to navigation met and adopted the IALA Maritime517.TheIALAMaritimeBuoyageSystemBuoyage System,They establishedtwo regions,RegionAand Region B, for the entire world. Region A roughly cor-Although most of the major maritime nations haveresponds to the 1936 League ofNations system, and Regionused either the lateral or the cardinal systemformanyyearsBto theolder 1889systemdetails suchas thebuoyshapes andcolorshavevariedfromLateralmarksdifferbetweenRegionsAand B.Lateralcountry to country.With the increase in maritime com-marks in Region A usered and green colors by day and night
72 SHORT RANGE AIDS TO NAVIGATION The charted position of a wreck buoy will usually be offset from the actual geographic position so that the wreck and buoy symbols do not coincide. Only on the largest scale chart will the actual and charted positions of both wreck and buoy be the same. Where they might overlap, it is the wreck symbol which occupies the exact charted position and the buoy symbol which is offset. Wreck buoys are required to be placed by the owner of the wreck, but they may be placed by the Coast Guard if the owner is unable to comply with this requirement. In general, privately placed aids are not as reliable as Coast Guard aids. Sunken wrecks are sometimes moved away from their buoys by storms, currents, freshets, or other causes. Just as shoals may shift away from the buoys placed to mark them, wrecks may shift away from wreck buoys. 515. Fallibility Of Buoys Buoys cannot be relied on to maintain their charted positions consistently. They are subject to a variety of hazards including severe weather, collision, mooring casualties, and electrical failure. Report any discrepancy noted in a buoy to the U.S. Coast Guard. The buoy symbol shown on charts indicates the approximate position of the sinker which secures the buoy to the seabed. The approximate position is used because of practical limitations in placing and keeping buoys and their sinkers in precise geographical locations. These limitations include prevailing atmospheric and sea conditions, the slope and type of material making up the seabed, the scope of the mooring chain, and the fact that the positions of the buoys and the sinkers are not under continuous surveillance. The position of the buoy shifts around the area shown by the chart symbol due to the forces of wind and current. A buoy may not be in its charted position because of changes in the feature it marks. For example, a buoy meant to mark a shoal whose boundaries are shifting might frequently be moved to mark the shoal accurately. A Local Notice To Mariners will report the change, and a Notice To Mariners chart correction may also be written. In some small channels which change often, buoys are not charted even when considered permanent; local knowledge is advised in such areas. For these reasons, a mariner must not rely completely upon the position or operation of buoys, but should navigate using bearings of charted features, structures, and aids to navigation on shore. Further, a vessel attempting to pass too close aboard a buoy risks a collision with the buoy or the obstruction it marks. BUOYAGE SYSTEMS 516. Lateral And Cardinal Systems There are two major types of buoyage systems: the lateral system and the cardinal system. The lateral system is best suited for well-defined channels. The description of each buoy indicates the direction of danger relative to the course which is normally followed. In principle, the positions of marks in the lateral system are determined by the general direction taken by the mariner when approaching port from seaward. These positions may also be determined with reference to the main stream of flood current. The United States Aids to Navigation System is a lateral system. The cardinal system is best suited for coasts with numerous isolated rocks, shoals, and islands, and for dangers in the open sea. The characteristic of each buoy indicates the approximate true bearing of the danger it marks. Thus, an eastern quadrant buoy marks a danger which lies to the west of the buoy. The following pages diagram the cardinal and lateral buoyage systems as found outside the United States. 517. The IALA Maritime Buoyage System Although most of the major maritime nations have used either the lateral or the cardinal system for many years, details such as the buoy shapes and colors have varied from country to country. With the increase in maritime commerce between countries, the need for a uniform system of buoyage became apparent. In 1889, an International Marine Conference held in Washington, D.C., recommended that in the lateral system, starboard hand buoys be painted red and port hand buoys black. Unfortunately, when lights for buoys were introduced some years later, some European countries placed red lights on the black port hand buoys to conform with the red lights marking the port side of harbor entrances, while in North America red lights were placed on red starboard hand buoys. In 1936, a League of Nations subcommittee recommended a coloring system opposite to the 1889 proposal. The International Association of Lighthouse Authorities (IALA) is a non-governmental organization which consists of representatives of the worldwide community of aids to navigation services to promote information exchange and recommend improvements based on new technologies. In 1980, with the assistance of IMO and the IHO, the lighthouse authorities from 50 countries and representatives of 9 international organizations concerned with aids to navigation met and adopted the IALA Maritime Buoyage System. They established two regions, Region A and Region B, for the entire world. Region A roughly corresponds to the 1936 League of Nations system, and Region B to the older 1889 system. Lateral marks differ between Regions A and B. Lateral marks in Region A use red and green colors by day and night