《航海学》课程参考文献（地文资料）CHAPTER 25 THE NAVIGATION PROCESS

CHAPTER 25THENAVIGATIONPROCESSINTRODUCTION2500.Fundamentalstem's optimum use varies as a function of the type of vessel,the quality of the navigation equipment on board, and the ex-perience and skill of the particular navigator.This chapter emphasizes the operational aspects of navi-For the watch officer, ensuring ship safety always takesgating in theopen ocean.It is in this operational process thatan individual navigator's experience and judgment becomepriorityovercompletingoperationalcommitmentsand car-mostcrucial.Compoundingthis subject'sdifficultyisthefactrying out the ship's routine.This chapter discusses severalthat there are no set rules regarding the optimum employmentbasic safety considerations designed tominimize theprob-of navigational systems and techniques.The navigation sys-ability of human error leading to a marine accident.VOYAGEPLANNINGVoyageplanning determines the safestand most effi-todetermine thepositionofresulting track points.Transfercient track fortheshipto followto ensurethatthevesselthesepoints to a Mercator chart asa succession of way-completes its operational commitments.Constructing apoints connected by rhumb lines.Figure 2501 illustratesplanned track for a voyage is fundamentally important forthis method.This figure shows a great circle route plottedship's safety.The commanding officer and the navigatoras a straight line on agnomonic chart and as a series ofmustcarefullyreviewandapprovethetrackfollowedbythepoints when transferred to a Mercator chart.The arrowsconning officer.Several ships'groundingshaveoccurred be-representcorrespondingpointsonthetwocharts.cause ofunauthorized deviations from an approvedtrack.An operation orderoften assigns a naval vessel to an op-eratingareaInthatcase,planatrackfromthedeparturetothe2501.ConstructingAVoyage Plan Trackedge of the operating area to ensure that the vessel arrives attheoperatingarea ontime.Following a planned track insideConstruct the track using a navigation computer, atheassigned areamaybe impossiblebecauseof thedynamicgreat circle (gnomonic) chart, or the sailings.This chapternature of a planned exercise. In that case,carefully examinewill discuss onlythenavigation computer and thegreatcir-theentireoperatingareafornavigationhazards.Ifsimplytranclechart.Chapter24coversthesailings.Useanavigationsiting through the area, the ship should still follow a plannedcomputer if one is available because the computer elimi-and approvedtrack.nates the plotting errors inherent in transferring the trackfromgnomonictoaMercatorprojectionWhen using a navigation computer,the navigator simply2502.Following AVoyage Planinputs the two endpoints of his planned voyage.The computercomputeswaypoints markingthegreatcircletrackbetweentheComplete the planning discussed in section 2501 priortwo endpoints. The computer determines each track leg's dis-toleavingport.Once the shipistransiting,frequently com-tance and, given a speed of advance, calculates the times thepare the ship's actual position to the planned position andvessel canexpecttopass eachwaypoint.Constructthetrackonadjust the ship's course and speed to compensatefor anythe Mercator chart by plotting the computer-generated way-deviations.Order coursesand speedstokeepthevessel onpoints andthetracks betweenthem.track without significantdeviation.After adjusting the track as necessary to pass well clear ofOften a vessel will have its operational commitmentsanyhazard,choosea speed ofadvance (SOA)that ensures thechanged after it gets underway.Ifthis happens, begin the voyageship will arrive on time at any required point. Given an SOAplanningprocess anew.Ensuretheship'snavigatorand captainmark the track with the ship's planned hourly positions. Theseapprovethenewtrack correspondingtothenewmissionTheplanned positions are points of intended movement (PIM's)conningofficermustunderstand that,unlesstransiting inan opThe SOA chosen for each track leg is the PIM speedIf a navigation computer is not available,usea gno-erating area as discussed above, he should never transit on amonic chart to plotagreat circleroutebetween points andchartthatdoesnothavean approved trackforhimtofollow.371

371 CHAPTER 25 THE NAVIGATION PROCESS INTRODUCTION 2500. Fundamentals This chapter emphasizes the operational aspects of navi￾gating in the open ocean. It is in this operational process that an individual navigator’s experience and judgment become most crucial. Compounding this subject’s difficulty is the fact that there are no set rules regarding the optimum employment of navigational systems and techniques. The navigation sys￾tem’s optimum use varies as a function of the type of vessel, the quality of the navigation equipment on board, and the ex￾perience and skill of the particular navigator. For the watch officer, ensuring ship safety always takes priority over completing operational commitments and car￾rying out the ship’s routine. This chapter discusses several basic safety considerations designed to minimize the prob￾ability of human error leading to a marine accident. VOYAGE PLANNING Voyage planning determines the safest and most effi￾cient track for the ship to follow to ensure that the vessel completes its operational commitments. Constructing a planned track for a voyage is fundamentally important for ship’s safety. The commanding officer and the navigator must carefully review and approve the track followed by the conning officer. Several ships’ groundings have occurred be￾cause of unauthorized deviations from an approved track. 2501. Constructing A Voyage Plan Track Construct the track using a navigation computer, a great circle (gnomonic) chart, or the sailings. This chapter will discuss only the navigation computer and the great cir￾cle chart. Chapter 24 covers the sailings. Use a navigation computer if one is available because the computer elimi￾nates the plotting errors inherent in transferring the track from gnomonic to a Mercator projection. When using a navigation computer, the navigator simply inputs the two endpoints of his planned voyage. The computer computes waypoints marking the great circle track between the two endpoints. The computer determines each track leg’s dis￾tance and, given a speed of advance, calculates the times the vessel can expect to pass each waypoint. Construct the track on the Mercator chart by plotting the computer-generated way￾points and the tracks between them. After adjusting the track as necessary to pass well clear of any hazard, choose a speed of advance (SOA) that ensures the ship will arrive on time at any required point. Given an SOA, mark the track with the ship’s planned hourly positions. These planned positions are points of intended movement (PIM’s). The SOA chosen for each track leg is the PIM speed. If a navigation computer is not available, use a gno￾monic chart to plot a great circle route between points and to determine the position of resulting track points. Transfer these points to a Mercator chart as a succession of way￾points connected by rhumb lines. Figure 2501 illustrates this method. This figure shows a great circle route plotted as a straight line on a gnomonic chart and as a series of points when transferred to a Mercator chart. The arrows represent corresponding points on the two charts. An operation order often assigns a naval vessel to an op￾erating area. In that case, plan a track from the departure to the edge of the operating area to ensure that the vessel arrives at the operating area on time. Following a planned track inside the assigned area may be impossible because of the dynamic nature of a planned exercise. In that case, carefully examine the entire operating area for navigation hazards. If simply tran￾siting through the area, the ship should still follow a planned and approved track. 2502. Following A Voyage Plan Complete the planning discussed in section 2501 prior to leaving port. Once the ship is transiting, frequently com￾pare the ship’s actual position to the planned position and adjust the ship’s course and speed to compensate for any deviations. Order courses and speeds to keep the vessel on track without significant deviation. Often a vessel will have its operational commitments changed after it gets underway. If this happens, begin the voyage planning process anew. Ensure the ship’s navigator and captain approve the new track corresponding to the new mission. The conning officer must understand that, unless transiting in an op￾erating area as discussed above, he should never transit on a chart that does not have an approved track for him to follow

372THENAVIGATIONPROCESSGNOMONICHMERCATORFigure2501.ConstructingagreatcircletrackonaMercatorprojectionVOYAGEPREPARATION2503.EquipmentInventoryquired for an open ocean or coastal transit. Complete thispreparation well before using the chart to maintain the plot.Prior togetting theship underway,inventory all navi-Correcting The Chart: Correct all applicable chartsgation equipment, charts,and publications.The navigatorthrough the latestNoticetoMariners,Local NoticetoMar-shoulddevelopachecklistofnavigationequipmentspecificto his vessel and check that all required equipment is on-iners,and Broadcast Noticeto Mariners.Ensure the charttoboard.Thenavigator shouldhave all applicable Sailingbe used is the correctedition.Directions,pilot charts,and navigation charts covering hisplanned route.He should also have all charts and sailing di-Plotting Approved Track: Section 2501 above discusS-rection coveringports at which his vessel maycall.Hees constructingthetrack.Markthetrackcourseabovethetrackshouldhaveall theequipmentand publications requiredtolinewith a“C"followed by the course. Similarly,mark eachsupport celestial navigation.Finally,hemust haveall tech-track leg's distance under the course line with aD"followednicaldocumentationrequiredtosupporttheoperationofhisby the distance in nautical miles. Mark the PIM's at hourly in-tervals, and mark the time corresponding to eachPIM.electronicnavigationsuiteCompletethischart,publication,andequipmentinven-tory well before the underway date and obtain all missingCalculating Minimum Expected, Danger, Anditems before sailingWarning Soundings: Chapter 8 discusses calculating mini-mumexpected,danger and warning soundings.Determining2504.Chart Preparationthese soundings is particularly important for ships passing ashoal close aboard.Set these soundings to warn the conningJust as the navigator must prepare charts for piloting,officer that he is passing too close to the shoal. Mark the min-he must also prepare his charts for an open ocean transit.imum expected sounding,thewarningsounding,and theThe following is a list ofthe minimum chart preparation re-danger soundingclearlyonthechart and indicate the section

372 THE NAVIGATION PROCESS VOYAGE PREPARATION 2503. Equipment Inventory Prior to getting the ship underway, inventory all navi￾gation equipment, charts, and publications. The navigator should develop a checklist of navigation equipment specific to his vessel and check that all required equipment is on￾board. The navigator should have all applicable Sailing Directions, pilot charts, and navigation charts covering his planned route. He should also have all charts and sailing di￾rection covering ports at which his vessel may call. He should have all the equipment and publications required to support celestial navigation. Finally, he must have all tech￾nical documentation required to support the operation of his electronic navigation suite. Complete this chart, publication, and equipment inven￾tory well before the underway date and obtain all missing items before sailing. 2504. Chart Preparation Just as the navigator must prepare charts for piloting, he must also prepare his charts for an open ocean transit. The following is a list of the minimum chart preparation re￾quired for an open ocean or coastal transit. Complete this preparation well before using the chart to maintain the plot. Correcting The Chart: Correct all applicable charts through the latest Notice to Mariners, Local Notice to Mar￾iners, and Broadcast Notice to Mariners. Ensure the chart to be used is the correct edition. Plotting Approved Track: Section 2501 above discuss￾es constructing the track. Mark the track course above the track line with a “C” followed by the course. Similarly, mark each track leg’s distance under the course line with a “D” followed by the distance in nautical miles. Mark the PIM’s at hourly in￾tervals, and mark the time corresponding to each PIM. Calculating Minimum Expected, Danger, And Warning Soundings: Chapter 8 discusses calculating mini￾mum expected, danger and warning soundings. Determining these soundings is particularly important for ships passing a shoal close aboard. Set these soundings to warn the conning officer that he is passing too close to the shoal. Mark the min￾imum expected sounding, the warning sounding, and the danger sounding clearly on the chart and indicate the section Figure 2501. Constructing a great circle track on a Mercator projection

THENAVIGATIONPROCESS373ofthe track for which they are applicable.be able to glean the entire navigation situation from thechart alone without reference to the directive from whichMarking Allowed Operating Areas: This chart prep-the chart was constructed.Therefore, put all operationallyaration step is applicable to militaryvessels.Often animportant information directly on the chart.operationorder assigns a naval vessel toan operating areaMarkingChart ShiftPoints:If thetransit will requirefor a specific period of time.Theremay be operational re-strictions placedon theshipwhilewithinthis area.Forthe ship to operate on more than one chart, mark the chartexample,a surface shipassigned to an operating area maypoints where the navigator must shift to the next chart.beorderednottoexceedacertainspeedforthedurationofan exercise.When assigned an operating area,clearlymarkExamining 50nmOn Either SideOf Track:High-that area on the chart.Label it with the time the vessel mustlight any shoal water or other navigationhazard withinremain intheareaand what,if any,operational restrictions5Onmoftheplannedtrack.Thiswill alerttheconningoffic-itmustfollow.The conning officer and thecaptain shoulder as heapproachesapossibledanger.NAVIGATIONROUTINEATSEA2505.FrequencyOfPositionDeterminationinvaluable formaintaining an accurate ship's position dur-ingperiods when external fix sourcesare unavailable.Thetablebelowlists recommended fixintervalsasaAlways check a position determined bya fix,inertialfunction of navigation phase:navigator, or DR by comparing the charted sounding at theposition with thefathometer reading.If the soundings donotcorrelate,investigatethediscrepancyPilotingCoastalOceanChapter7coverstheimportanceofmaintainingaprop-er DR.It bears repeating here.Determine the difference3-15 min.30 min.Frequency3min.or lessbetween the fix and theDR positions at every fix and usethis information to calculatean EPfrom everyDR.Con-Shorten the suggested fix interval if required to ensurestant application of set and drift to the DR is crucial if thethevesselremainsatleasttwofixintervalsfromthenearestvessel mustpassaknownnavigationhazard closeaboarddanger.However, do not exceed the times recommendedabove.Choosea fix interval that provides a sufficient safety2506.FathometerOperationsmargin from all chartedhazards.Use all available fix information. With the advent ofUse Figure 2506 to develop a standard procedure foraccurate satellitenavigation systems,it is especiallytemptoperating the fathometer.ing to disregard this maxim. However, the experiencednavigatorneverfeelscomfortablerelying solelyononepar-2507.The Modified Piloting Partyticular system. Supplement the satellite position withpositions from Loran, celestial sights,radar lines of posi-Ifoperating out ofpiloting waters but near anavigationtion, and visual observations.Evaluate the accuracy of thehazard,station a modified piloting party.As the name im-various fix methods against the satellite position, when theplies,this team does not consist ofthe entirepilotingpartysatellitereceiverfails,theknowledge,forexample,that Loran fixes consistently plotted1nmto thewest ofGPS canItcouldconsistofonlythenavigatororassistantnavigator,be helpful.a plotter,and a recorder.Its purpose is to increase supervi-sion ofthe navigation plot in areas that could pose a hazardUsean inertial navigator if one is available.The inertialto the vessel.navigatormay produce estimatedpositionsmoreaccurateThe navigator and captain should develop a standing or-than fix positions.Inertial navigators are completely inde-pendent of any external fix input. Therefore, they areder covering the stationing of a modified piloting party. AWaterDepthSounding IntervalChartedWaterDepth 1000 ft.Take and record soundings every hourFigure2506.Fathometeroperatingguidelines

THE NAVIGATION PROCESS 373 of the track for which they are applicable. Marking Allowed Operating Areas: This chart prep￾aration step is applicable to military vessels. Often an operation order assigns a naval vessel to an operating area for a specific period of time. There may be operational re￾strictions placed on the ship while within this area. For example, a surface ship assigned to an operating area may be ordered not to exceed a certain speed for the duration of an exercise. When assigned an operating area, clearly mark that area on the chart. Label it with the time the vessel must remain in the area and what, if any, operational restrictions it must follow. The conning officer and the captain should be able to glean the entire navigation situation from the chart alone without reference to the directive from which the chart was constructed. Therefore, put all operationally important information directly on the chart. Marking Chart Shift Points: If the transit will require the ship to operate on more than one chart, mark the chart points where the navigator must shift to the next chart. Examining 50nm On Either Side Of Track: High￾light any shoal water or other navigation hazard within 50nm of the planned track. This will alert the conning offic￾er as he approaches a possible danger. NAVIGATION ROUTINE AT SEA 2505. Frequency Of Position Determination The table below lists recommended fix intervals as a function of navigation phase: Shorten the suggested fix interval if required to ensure the vessel remains at least two fix intervals from the nearest danger. However, do not exceed the times recommended above. Choose a fix interval that provides a sufficient safety margin from all charted hazards. Use all available fix information. With the advent of accurate satellite navigation systems, it is especially tempt￾ing to disregard this maxim. However, the experienced navigator never feels comfortable relying solely on one par￾ticular system. Supplement the satellite position with positions from Loran, celestial sights, radar lines of posi￾tion, and visual observations. Evaluate the accuracy of the various fix methods against the satellite position; when the satellite receiver fails, the knowledge, for example, that Lo￾ran fixes consistently plotted 1 nm to the west of GPS can be helpful. Use an inertial navigator if one is available. The inertial navigator may produce estimated positions more accurate than fix positions. Inertial navigators are completely inde￾pendent of any external fix input. Therefore, they are invaluable for maintaining an accurate ship’s position dur￾ing periods when external fix sources are unavailable. Always check a position determined by a fix, inertial navigator, or DR by comparing the charted sounding at the position with the fathometer reading. If the soundings do not correlate, investigate the discrepancy. Chapter 7 covers the importance of maintaining a prop￾er DR. It bears repeating here. Determine the difference between the fix and the DR positions at every fix and use this information to calculate an EP from every DR. Con￾stant application of set and drift to the DR is crucial if the vessel must pass a known navigation hazard close aboard. 2506. Fathometer Operations Use Figure 2506 to develop a standard procedure for operating the fathometer. 2507. The Modified Piloting Party If operating out of piloting waters but near a navigation hazard, station a modified piloting party. As the name im￾plies, this team does not consist of the entire piloting party. It could consist of only the navigator or assistant navigator, a plotter, and a recorder. Its purpose is to increase supervi￾sion of the navigation plot in areas that could pose a hazard to the vessel. The navigator and captain should develop a standing or￾der covering the stationing of a modified piloting party. A Piloting Coastal Ocean Frequency 3 min. or less 3-15 min. 30 min. Water Depth Sounding Interval Charted Water Depth 1000 ft. Take and record soundings every hour. Figure 2506. Fathometer operating guidelines

374THENAVIGATIONPROCESSgood rule is to station the modified piloting party when operat-0800.1200,and2000eachday.Preparethesereportsapproxingwithin10nmofaknownhazardimately30minutes ahead of the time when theyare due.UsetheDRpositionsforthetimeofthereportForexample,pre-2508.CompassChecksparethe2000position reportat1930usingtheship's2000DRposition.Often thecaptainwill requireadditional informationwiththesepositionreports.Somecaptains,forexample,mayDetermine gyro compass error at least daily as part ofwantstatusreports ontheengineroom.Tailoreachpositionre-the at-sea routine.Check the gyro compass reading againstportto containthe informationthecaptain wants.the inertial navigator if the vessel has an inertial navigatorIf the vessel does not have an inertial navigator, check gyro2511.WatchRelief ProcedureserrorusingthecelestialtechniguesdiscussedinChapter17Report any error greater than 1to the navigator and com-When a watch officer relieves as Officer of the Deckmanding officer.(OOD), he assumes the responsibility for the safe naviga-Check the gyro repeaters and the magnetic compasstionoftheship.Hebecomes theCommandingOfficer'sagainstthegyro compasshourly and after each coursedirect representative in ensuring ship safety.As such,hechange.Whencomparingthemagneticandgyrocompasses,must prepare himselffully prior to assuming the watch.Theaccountforchanges invariationanddeviation.Reportanyfollowing list contains those items that, as a minimum,therepeater error greater than 1°to the commanding officer.relievingOODmustcheckpriortoassumingthewatch.2509.Commanding Officer's Night Orders AndStanding OrdersConduct a Pre Watch Tour:The relieving OODshould tour the ship prior to his watch.He should fa-The Night Order book isthe vehiclebywhich the cap-miliarize himself with any maintenance in progress.taininformstheofficerofthedeckofthecaptain'sordersHe should check for general cleanliness and stow-for operating the ship.The Night Orderbook,despite itsage.He should order any loose gear that could posename,can contain ordersfortheentire24 hourperiod aftera safety hazard in rough seas secured.which the CO issues it.The navigatormaywrite theNight Orders pertainingto.Check the Position Log and Chart: Check the typenavigation. Such orders include assigned operating areas,and accuracy ofthe ship's lastfix.Verifythat the nav-maximum speeds allowed,required positions with respecttoigation watch has plotted the last fix properly.EnsurePIM, and, regarding submarines,the maximum depth atthere is a properly constructed DR plot on the chartwhich the ship can operate.Each department head should in-ExaminetheDRforanypotentialnavigationhazardsclude in the Night Order book the evolutions he wants toCheckship's position withrespecttothePIM.Ensureaccomplish during the night that would normally require thethattheship is in the corectoperating area, ifapplica-captain's permission,The captain can add further orders andble.Check toensure that the navigation watchhasdirections as required.When the captain signs theNightOrderproperly appliedfixexpansion in accordance withthebook.itbecomesanoficialordertotheOfficeroftheDeck.navigator's instructions.The Officer of the Deck must notfollowtheNight Or-ders blindly.Circumstances under which the captain signed.Check the Fathometer Log:Ensure that previousthe Orders may have changed,rendering some evolutionswatches have taken soundings at required intervals andordered impractical to complete.The Officer of theDeckthatthenavigationwatchtooka soundingatthelastfixwhen exercisinghis judgment on completing ordered evo-Verifythat thepresent soundingmatches the chartedlutions,mustalways informthecaptain of anydeviationsounding at the vessel's charted position.fromtheNightOrdersassoonas suchadeviationoccursThe Commanding Officer's Night Orders are in effect.Check the Compass Record Log:Verify that theonlyfor the 24 hours after they are written;his Standing Or-navigation watch has conducted compass checks atders are continuously in force. The captain sets the ship'sthe proper interval. Verify that gyro error is less thannavigation policy in these orders. He sets required fix inter-10 and that all repeaters agree within 1° with thevals, intervalsfor fathometer operations,minimum CPA'smastergyro.and othergeneral navigation and collision avoidancerequire-ments.TheOfficeroftheDeckmustfollowtheCommanding.Read the Commanding Officer Night Orders:Officer's Standing Orders at all times.Report any deviationCheckthe Night Order Book for thecaptain's direc-from these orders immediatelyto the Commanding Officer.tions for the duration of thewatch.2510.Position Reports.CheckPlanned Operations:For anyplannedopera-tions, verify that the ship has met all operationalIf the captain requires position reports, deliver them atprerequisites, that the ship is in the correct operating

374 THE NAVIGATION PROCESS good rule is to station the modified piloting party when operat￾ing within 10 nm of a known hazard. 2508. Compass Checks Determine gyro compass error at least daily as part of the at-sea routine. Check the gyro compass reading against the inertial navigator if the vessel has an inertial navigator. If the vessel does not have an inertial navigator, check gyro error using the celestial techniques discussed in Chapter 17. Report any error greater than 1° to the navigator and com￾manding officer. Check the gyro repeaters and the magnetic compass against the gyro compass hourly and after each course change. When comparing the magnetic and gyro compasses, account for changes in variation and deviation. Report any repeater error greater than 1° to the commanding officer. 2509. Commanding Officer’s Night Orders And Standing Orders The Night Order book is the vehicle by which the cap￾tain informs the officer of the deck of the captain’s orders for operating the ship. The Night Order book, despite its name, can contain orders for the entire 24 hour period after which the CO issues it. The navigator may write the Night Orders pertaining to navigation. Such orders include assigned operating areas, maximum speeds allowed, required positions with respect to PIM, and, regarding submarines, the maximum depth at which the ship can operate. Each department head should in￾clude in the Night Order book the evolutions he wants to accomplish during the night that would normally require the captain’s permission. The captain can add further orders and directions as required. When the captain signs the Night Order book, it becomes an official order to the Officer of the Deck. The Officer of the Deck must not follow the Night Or￾ders blindly. Circumstances under which the captain signed the Orders may have changed, rendering some evolutions ordered impractical to complete. The Officer of the Deck, when exercising his judgment on completing ordered evo￾lutions, must always inform the captain of any deviation from the Night Orders as soon as such a deviation occurs. The Commanding Officer’s Night Orders are in effect only for the 24 hours after they are written; his Standing Or￾ders are continuously in force. The captain sets the ship’s navigation policy in these orders. He sets required fix inter￾vals, intervals for fathometer operations, minimum CPA’s, and other general navigation and collision avoidance require￾ments. The Officer of the Deck must follow the Commanding Officer’s Standing Orders at all times. Report any deviation from these orders immediately to the Commanding Officer. 2510. Position Reports If the captain requires position reports, deliver them at 0800, 1200, and 2000 each day. Prepare these reports approx￾imately 30 minutes ahead of the time when they are due. Use the DR positions for the time of the report. For example, pre￾pare the 2000 position report at 1930 using the ship’s 2000 DR position. Often the captain will require additional information with these position reports. Some captains, for example, may want status reports on the engine room. Tailor each position re￾port to contain the information the captain wants. 2511. Watch Relief Procedures When a watch officer relieves as Officer of the Deck (OOD), he assumes the responsibility for the safe naviga￾tion of the ship. He becomes the Commanding Officer’s direct representative in ensuring ship safety. As such, he must prepare himself fully prior to assuming the watch. The following list contains those items that, as a minimum, the relieving OOD must check prior to assuming the watch. • Conduct a Pre Watch Tour: The relieving OOD should tour the ship prior to his watch. He should fa￾miliarize himself with any maintenance in progress. He should check for general cleanliness and stow￾age. He should order any loose gear that could pose a safety hazard in rough seas secured. • Check the Position Log and Chart: Check the type and accuracy of the ship’s last fix. Verify that the nav￾igation watch has plotted the last fix properly. Ensure there is a properly constructed DR plot on the chart. Examine the DR for any potential navigation hazards. Check ship’s position with respect to the PIM. Ensure that the ship is in the correct operating area, if applica￾ble. Check to ensure that the navigation watch has properly applied fix expansion in accordance with the navigator’s instructions. • Check the Fathometer Log: Ensure that previous watches have taken soundings at required intervals and that the navigation watch took a sounding at the last fix. Verify that the present sounding matches the charted sounding at the vessel’s charted position. • Check the Compass Record Log: Verify that the navigation watch has conducted compass checks at the proper interval. Verify that gyro error is less than 1° and that all repeaters agree within 1° with the master gyro. • Read the Commanding Officer Night Orders: Check the Night Order Book for the captain’s direc￾tions for the duration of the watch. • Check Planned Operations: For any planned opera￾tions, verify that the ship has met all operational prerequisites, that the ship is in the correct operating

375THENAVIGATIONPROCESSarea,and that all watchstanders havereviewed the op-relievethewatch.TheonwatchOODthenshouldbrieftheeration order.If theoperation is a complicated onerelievingOODonthefollowingconsider holdingan operations briefwith applicable.Vessel's present course and speedwatchstanderspriortoassumingthewatch.Vessel'spresentdepth(submarines only):Check the Broadcast Schedule: Read any messageAnyevolutions planned or in progress.traffic that could have a bearing on the upcoming.The status of the engineering plant.watch.Ifthe ship ison a broadcast schedule, find out·Thestatus of repair on any out of commission equip-whentheradiooperatorreceivedthelastbroadcasment that effects the ship's operational capability.(military vessels only).Determine ifthe radiooperator.AnyordersfromtheCommandingOfficernotex-has anymessagesto transmit during the watch.presslygiven in the Night Orders..Status of cargo (merchant vessels only)..Ascertain the Contact Situation: Check the radar andAnyhazardous maintenanceplanned orinprogress..Any routine maintenance planned or in progress.sonar contact picture, if so equipped.Determine whichAny planned ship's drills.contacthastheclosestCPAandwhatmaneuvers,ifany,willberequiredtoopenCPAFindoutfromtheoffgoingIf the relieving OOD has no questions following thisOOD if there have beenanybridge-to-bridge communi-brief, then he should relieve the watch.Upon relieving thecations with anyvessels in the area.Check that noCPAwill be less than theminimum set by theCommandingwatch, he should announceto both the helmsman and theOfficer's StandingOrders.quartermaster that he has the deck and the conn.Thequar-termaster should log the change of watch in the ship's deck.ReviewWatchstander Logs:Reviewthe log readingslogfor all watchstanders.Note any out of specificationWatch officers should not relievethewatch in the mid-readings or any trends in log readings indicating that adle of an evolution or when casualtyprocedures arebeingparameter will soon go out of specification.carried out. Relieve the watch only during a steady state operational and tactical situation. This ensures that thereisAfter conducting the above listed checks,therelievingwatchstander continuity when carrying out a specific evo-OODshouldreporttotheonwatchOODthatheisreadytolutionorcombatinga casualtyTHEDAY'SWORKINCELESTIALNAVIGATIONThe advent of accurate electronic and satellite naviga-5.Calculatean azimuth of the sun for a compasstion systems has relegated celestial navigation to use solelycheck.The navigator normally obtains an azi-as a backup navigation method. Seldom ifever will a shipmuth at aboutthe sametimeas hetakes a morningundertake an ocean transit relyingonly on celestial naviga-sunobservation.Hemayalsocheckthecompasstion.Therefore.thenavigatorneednotfollowtheentirewith an amplitude observation at sunriseroutine listed belowifcelestial navigation isnothisprimary6.Observethe sun at local apparentnoon.Crossnavigation source.Use only the steps of the celestial day'sthe resulting LOP with an advanced morningwork that arenecessaryto provide a meaningful check onsun line or with a longitude determined at LANthe primary fix source's accuracy.Should the electronicfora fix or running fix.navigation systemfail,however,and shouldcelestial navi7. Reduce a sun sight during the afternoon. Thisgation become the primary means of navigation, thisis primarilyforusewith an advanced noon sunsectionprovidesacomprehensiveproceduretofollowline, or with a moonor Venus line,ifthe skies2512.Celestial Navigation Routineare overcast during evening twilight8.Calculate an azimuth of the sun for a compassComplete a typical day's work in open celestial navi-check ataboutthe sametime asthe afternoon sungation as follows:observation. The navigator may replace this azi-muth with an amplitudeobservation at sunset.1. Plot the dead reckoning position.9.Reduce celestial observations for a fix during2.Reduce celestial observations for a fix duringevening twilight.morning twilight.3.Windthe chronometerand determine chro-Chapter7,Chapter17,and Chapter20contain detailed exnometererror.4. Reduce a sun sight for a morning sun line.planations of theprocedures required to carry out thisroutine

THE NAVIGATION PROCESS 375 area, and that all watchstanders have reviewed the op￾eration order. If the operation is a complicated one, consider holding an operations brief with applicable watchstanders prior to assuming the watch. • Check the Broadcast Schedule: Read any message traffic that could have a bearing on the upcoming watch. If the ship is on a broadcast schedule, find out when the radio operator received the last broadcast (military vessels only). Determine if the radio operator has any messages to transmit during the watch. • Ascertain the Contact Situation: Check the radar and sonar contact picture, if so equipped. Determine which contact has the closest CPA and what maneuvers, if any, will be required to open CPA. Find out from the offgoing OOD if there have been any bridge-to-bridge communi￾cations with any vessels in the area. Check that no CPA will be less than the minimum set by the Commanding Officer’s Standing Orders. • Review Watchstander Logs: Review the log readings for all watchstanders. Note any out of specification readings or any trends in log readings indicating that a parameter will soon go out of specification. After conducting the above listed checks, the relieving OOD should report to the on watch OOD that he is ready to relieve the watch. The on watch OOD then should brief the relieving OOD on the following: • Vessel’s present course and speed. • Vessel’s present depth (submarines only). • Any evolutions planned or in progress. • The status of the engineering plant. • The status of repair on any out of commission equip￾ment that effects the ship’s operational capability. • Any orders from the Commanding Officer not ex￾pressly given in the Night Orders. • Status of cargo (merchant vessels only). • Any hazardous maintenance planned or in progress. • Any routine maintenance planned or in progress. • Any planned ship’s drills. If the relieving OOD has no questions following this brief, then he should relieve the watch. Upon relieving the watch, he should announce to both the helmsman and the quartermaster that he has the deck and the conn. The quar￾termaster should log the change of watch in the ship’s deck log. Watch officers should not relieve the watch in the mid￾dle of an evolution or when casualty procedures are being carried out. Relieve the watch only during a steady state op￾erational and tactical situation. This ensures that there is watchstander continuity when carrying out a specific evo￾lution or combating a casualty. THE DAY’S WORK IN CELESTIAL NAVIGATION The advent of accurate electronic and satellite naviga￾tion systems has relegated celestial navigation to use solely as a backup navigation method. Seldom if ever will a ship undertake an ocean transit relying only on celestial naviga￾tion. Therefore, the navigator need not follow the entire routine listed below if celestial navigation is not his primary navigation source. Use only the steps of the celestial day’s work that are necessary to provide a meaningful check on the primary fix source’s accuracy. Should the electronic navigation system fail, however, and should celestial navi￾gation become the primary means of navigation, this section provides a comprehensive procedure to follow. 2512. Celestial Navigation Routine Complete a typical day’s work in open celestial navi￾gation as follows: 1. Plot the dead reckoning position. 2. Reduce celestial observations for a fix during morning twilight. 3. Wind the chronometer and determine chro￾nometer error. 4. Reduce a sun sight for a morning sun line. 5. Calculate an azimuth of the sun for a compass check. The navigator normally obtains an azi￾muth at about the same time as he takes a morning sun observation. He may also check the compass with an amplitude observation at sunrise. 6. Observe the sun at local apparent noon. Cross the resulting LOP with an advanced morning sun line or with a longitude determined at LAN for a fix or running fix. 7. Reduce a sun sight during the afternoon. This is primarily for use with an advanced noon sun line, or with a moon or Venus line, if the skies are overcast during evening twilight. 8. Calculate an azimuth of the sun for a compass check at about the same time as the afternoon sun observation. The navigator may replace this azi￾muth with an amplitude observation at sunset. 9. Reduce celestial observations for a fix during evening twilight. Chapter 7, Chapter 17, and Chapter 20 contain detailed ex￾planations of the procedures required to carry out this routine

376THENAVIGATIONPROCESSPOSITIONPLOTTINGSHEET142"WD29Figure 2512.Typical celestial plot at sea.SPECIALCONSIDERATIONSFORSMALLCRAFT2513.NavigationOfSmallCraftor Sailing Directions,and binocularsAll craft venturing offshore should carryaproperlyIn principle,thenavigationofsmall craft is the same asregisteredEPIRBand VHFradio.LoranC.Omega,andGPS receivers are available; boats that transit out of sight ofthat of larger vessels.However, because of a small craft'sshallower draftgreatermaneuverability,and possible lim-land shouldhaveatleast oneof theseIf the craft is to proceed out of sight of land for moreitations of equipment and expertise, there are importantthan short intervals, celestial navigation equipment shoulddifferences.Smallcraft oftenspendmostoftheirtimewith-in sightof land,and theirnavigation islargelya matter ofbe aboard.This equipment should include a sextant, an ac-piloting. They generally are close enough inshore to reachcuratetimepiece, a means of receiving time signals, ansafety in case of storm or fog.Sincemost of them arepri-almanac, and sight reduction tables. Celestial navigationmarily pleasure craft, there is a tendency for theircalculators orcomputerprograms arealso usefulnavigation tobea less professional processthan in com-Asmall craftnavigator of limited experiencemayun-mercialormilitarycraftderestimate the importance of professional navigationRegardless ofthenatureofthecraft,it should carrytheHowever,his vessel's safety depends on his skill.Hemustminimum safety equipment required by the U.S. Coastplanhis trackandknow hisposition at all times.Small craftGuard. In addition to thisCoast Guard mandated safetynavigationalsorequiresacomplete,accurate,andneatplotequipment, a small craft should also carry a compass,Wherethis is impractical because of heavyweather or limit-charts,plottingdevices,speedlog,tidetables,CoastPiloedplottingspace,use a careful loganddead reckoningplot

376 THE NAVIGATION PROCESS SPECIAL CONSIDERATIONS FOR SMALL CRAFT 2513. Navigation Of Small Craft In principle, the navigation of small craft is the same as that of larger vessels. However, because of a small craft’s shallower draft, greater maneuverability, and possible lim￾itations of equipment and expertise, there are important differences. Small craft often spend most of their time with￾in sight of land, and their navigation is largely a matter of piloting. They generally are close enough inshore to reach safety in case of storm or fog. Since most of them are pri￾marily pleasure craft, there is a tendency for their navigation to be a less professional process than in com￾mercial or military craft. Regardless of the nature of the craft, it should carry the minimum safety equipment required by the U.S. Coast Guard. In addition to this Coast Guard mandated safety equipment, a small craft should also carry a compass, charts, plotting devices, speed log, tide tables, Coast Pilot or Sailing Directions, and binoculars. All craft venturing offshore should carry a properly registered EPIRB and VHF radio. Loran C, Omega, and GPS receivers are available; boats that transit out of sight of land should have at least one of these. If the craft is to proceed out of sight of land for more than short intervals, celestial navigation equipment should be aboard. This equipment should include a sextant, an ac￾curate timepiece, a means of receiving time signals, an almanac, and sight reduction tables. Celestial navigation calculators or computer programs are also useful. A small craft navigator of limited experience may un￾derestimate the importance of professional navigation. However, his vessel’s safety depends on his skill. He must plan his track and know his position at all times. Small craft navigation also requires a complete, accurate, and neat plot. Where this is impractical because of heavy weather or limit￾ed plotting space, use a careful log and dead reckoning plot. Figure 2512. Typical celestial plot at sea

377THENAVIGATIONPROCESSCONCLUSION2514.The Importance OfThe Navigation Processposition enroute are fundamental concepts of safe naviga-tion.A mariner should never feel comfortable unless he isNavigating a vessel is a dynamic process. Schedulesfollowinganapproved trackplottedona correctedchart onwhich he has frequently updated his position.change, missions change. Planning a voyage is a process that be-gins well beforetheshipgets underway.Executingthat plandoesDeveloping and implementing such a routine is onlynot end until the ship ties up at the pier at its final destination.halfofthebattle.Watchstandersmust follow approved pro-cedures. U.S. Navy grounding reports and U.S. CoastDevelopa navigation process encompassing the princi-ples discussed in this chapter. Carefully planning a route,Guard accident reports attest to the danger courted when avessel disregards basic navigation safety.preparing required charts, and closely monitoring the ship's

THE NAVIGATION PROCESS 377 CONCLUSION 2514. The Importance Of The Navigation Process Navigating a vessel is a dynamic process. Schedules change; missions change. Planning a voyage is a process that be￾gins well before the ship gets underway. Executing that plan does not end until the ship ties up at the pier at its final destination. Develop a navigation process encompassing the princi￾ples discussed in this chapter. Carefully planning a route, preparing required charts, and closely monitoring the ship’s position enroute are fundamental concepts of safe naviga￾tion. A mariner should never feel comfortable unless he is following an approved track plotted on a corrected chart on which he has frequently updated his position. Developing and implementing such a routine is only half of the battle. Watchstanders must follow approved pro￾cedures. U.S. Navy grounding reports and U.S. Coast Guard accident reports attest to the danger courted when a vessel disregards basic navigation safety