Witherby Seamanship International A Division of Witherby Publishing Group Ltd 4 Dunlop Square, Livingston, Edinburgh, EH54 8SB, Scotland, UK Tel No: +44(0)1506 463 227 - Fax No: +44(0)1506 468 999 Email: info@emailws.com - Web: www.witherbyseamanship.com NAVIGATIONADVANCEDMATES/MASTERS SECOND EDITION Captain Nadeem Anwar v Captain Nadeem Anwar Captain Nadeem Anwar, FNI, MSc, BSc, ACII, CertEd, PGCEL, Master Mariner, is a Curriculum Manager at Fleetwood Nautical Campus, UK. Captain Anwar has written several other books including ‘Ballast Water Management’ and ‘Passage Planning’. He has also contributed to various other titles, developed training courses and written a range of training materials. He also provides consultancy services to marine-training providers and shipping companies. Captain Anwar has 14 years experience of being at sea on a variety of ships, including multipurpose vessels, car carriers, VLCC, OBO, O/O, Gas and Chemical Tankers. He has substantial experience of being at a senior level on board ships, including being in command. He has navigated worldwide and gained substantial experience of different extreme environmental conditions and sea areas, gaining a wealth of navigational experience. He has had a successful career as an academic and a professional. In 2005, he achieved an MSc in Maritime Operations with a Distinction (Liverpool John Moores University) as well as an Advanced Diploma in Insurance (through the Chartered Insurance Institute, London). Captain Anwar was recently in the Arabian Gulf, where he was exposed to modern developments and current industrial practices. His consultancy base expanded significantly while working in the Gulf as the Managing Director of leading international companies. viivii Author’s Preface Navigational inaccuracies have mainly been the source of most of the catastrophic maritime disasters. The industry is heavily legislated and more regulations are likely to be developed in the near future. It is important to understand that it is the basic skills of the seafarers, especially the navigators who are the main stay of maritime safety. There are increasing concerns about the competence and skills of seafarers, in particular the navigation watchkeepers. The training and development of seafarers is time consuming, costly and demanding. There is also the need to keep the knowledge current by staying abreast of the new developments and practices. This book is aimed at the navigator of today and of the future. The increasing workload on the watchkeeper demands simple methods of working and, clear and concise instructions, so that the navigator can spend more time concentrating on watchkeeping. The methods of working used in the book are not just easy to follow for learning, but are also for on board applications. It contains a number of worked examples, plots, templates for working and exercises to allow the navigator to gain basic and advanced navigation skills. The book not only mentions the methods, it explains the methods. The future of maritime safety, to a large extent, relies on advanced navigational skills. The book is aimed at Masters and senior navigation officers and would also be beneficial for the junior navigation officers as it would help them to gain knowledge and develop skills for shipboard applications, and also for future career progression. ixix Contents Author’s Preface.......................................................................................................................................................vii 1Regulatory Requirements..................................................................................................................................1 1.1STCW.......................................................................................................................................................1 1.2 Safe Manning............................................................................................................................................2 1.3SOLAS Chapter V.....................................................................................................................................3 1.3.1Reports by the Master ................................................................................................................3 1.4ISM Code..................................................................................................................................................6 1.4.1SMS............................................................................................................................................6 1.4.2The Master’s Responsibility........................................................................................................6 1.4.3Simplified Compliance ................................................................................................................7 1.5Bridge Procedures Guide .........................................................................................................................7 1.5.1Contents .....................................................................................................................................7 1.6BNWAS.....................................................................................................................................................8 1.7Buoyage....................................................................................................................................................9 1.7.1Direction of Buoyage and Distance ............................................................................................9 1.7.2Special Marks ...........................................................................................................................13 1.7.3New Dangers............................................................................................................................14 1.8ISPS ........................................................................................................................................................14 1.9Pollution..................................................................................................................................................14 1.10Guidance from a Flag State ....................................................................................................................14 1.10.1Merchant Shipping Notices (MSN)...........................................................................................14 1.10.2Marine Guidance Notes (MGN) ................................................................................................14 1.10.3Marine Information Notices (MIN).............................................................................................14 1.10.4 Carriage Requirements for Publications ...................................................................................14 1.11Voyage Data Recorder ...........................................................................................................................15 1.12Standing and Night Orders .....................................................................................................................16 1.12.1Standing Orders .......................................................................................................................16 1.12.2Night Orders .............................................................................................................................17 2Passage Planning.............................................................................................................................................19 2.1Appraisal.................................................................................................................................................19 2.1.1Use of Publications ...................................................................................................................20 2.1.2Other Sources of Information ...................................................................................................22 2.1.3Chart 5500................................................................................................................................27 2.1.4 Charts and Associated Publications – Reliance .......................................................................28 2.2Planning..................................................................................................................................................29 2.2.1Berth-to-Berth Planning ............................................................................................................29 2.2.2Passage Plan Format ...............................................................................................................29 2.3Summary of General Principles ..............................................................................................................31 2.3.1Explanation of Planning Methods.............................................................................................31 2.4Execution................................................................................................................................................39 2.4.1Bridge Resource Management .................................................................................................39 2.5Monitoring...............................................................................................................................................40 2.5.1Position Fixing..........................................................................................................................40 2.5.2Visual Monitoring Techniques ...................................................................................................41 2.5.3Ship’s Profile and Datum Shift ..................................................................................................44 2.5.4Non-Visual Monitoring Techniques...........................................................................................45 2.6Summary................................................................................................................................................46 3Sailings..............................................................................................................................................................47 3.1The Terrestrial Sphere ............................................................................................................................47 3.1.1Position Reference ...................................................................................................................48 3.1.2Direction Reference..................................................................................................................49 3.1.3Distances..................................................................................................................................51 x Navigation Advanced Mates/Masters 3.2Parallel Sailing........................................................................................................................................51 3.3Plane Sailing...........................................................................................................................................52 3.3.1Use of Mean Latitude...............................................................................................................53 3.3.2Application of Traverse Sailing.................................................................................................54 3.4Mercator Sailing......................................................................................................................................55 3.5Great Circle Sailing.................................................................................................................................56 3.5.1Distance....................................................................................................................................57 3.5.2Courses....................................................................................................................................57 3.5.3 Napier’s Rules and Trigonometric Identities .............................................................................59 3.5.4Vertex .......................................................................................................................................59 3.5.5Crossing the Equator................................................................................................................60 3.5.6Latitude at a Meridian ...............................................................................................................61 3.6Composite Great Circle ..........................................................................................................................65 3.7Practical Applications ..............................................................................................................................66 3.7.1Use of Gnomonic Chart ............................................................................................................66 3.7.2Modifying the Routes................................................................................................................68 4Ocean Routeing................................................................................................................................................73 4.1Use of Charts and Publications ..............................................................................................................73 4.1.1Ocean Passages for the World .................................................................................................73 4.1.2Charts.......................................................................................................................................74 4.1.3Current Charts ..........................................................................................................................75 4.2Choice of Routes....................................................................................................................................77 4.2.1Operator Considerations ..........................................................................................................77 4.2.2Master’s Considerations ...........................................................................................................77 4.2.3Weather Routeing - Shore-Based .............................................................................................78 4.3 Oceanographic and Climatic Data..........................................................................................................81 4.3.1Ocean Currents and Climatic Data...........................................................................................81 4.4 General Hazards to be Found on an Ocean Passage............................................................................90 4.4.1 Recap of Factors for Choice of Routes ....................................................................................90 5Bridge Procedures............................................................................................................................................93 5.1Bridge Organisation................................................................................................................................93 5.1.1Navigational Watch Composition..............................................................................................93 5.1.2Engineering Watch ...................................................................................................................95 5.1.3Fitness for Watch and Rest Periods.........................................................................................96 5.2Keeping Watch.......................................................................................................................................97 5.2.1 Familiarisation with Bridge Equipment.....................................................................................97 5.2.2Keeping the Watch ...................................................................................................................98 5.2.3General Watchkeeping ...........................................................................................................100 5.3Navigation.............................................................................................................................................101 5.3.1Anchoring...............................................................................................................................102 5.3.2Towing and Navigation ...........................................................................................................103 5.3.3CollisionAvoidance .................................................................................................................104 5.4Use of Pilot...........................................................................................................................................105 5.4.1Reasons.................................................................................................................................105 5.4.2Initial Information Exchange...................................................................................................106 5.4.3Navigation With a Pilot on Board ............................................................................................106 5.4.4Responsibilities.......................................................................................................................107 5.4.5Monitoring the Pilotage...........................................................................................................107 5.4.6Information on the Pilot Card..................................................................................................108 5.5Procedures...........................................................................................................................................108 5.5.1Restricted Visibility ..................................................................................................................108 5.5.2 Malfunction of Navigational Equipment..................................................................................110 5.5.3Piracy ......................................................................................................................................110 5.5.4Pre-Departure Procedures......................................................................................................111 5.5.5Pre-Arrival Procedures ............................................................................................................111 5.6NavigationalRisk Assessment...............................................................................................................111 5.6.1ExampleRisk Assessment .....................................................................................................112 5.7 Hydrographic and Port Information .......................................................................................................113 5.7.1Hydrographic Information .......................................................................................................113 5.7.2Port Information ......................................................................................................................114 Contents xi 6Radar Navigation............................................................................................................................................115 6.1Radar Displays.....................................................................................................................................115 6.1.1Relative Motion .......................................................................................................................115 6.1.2True Motion .............................................................................................................................116 6.1.3Interpretation of Vectors and Trails .........................................................................................116 6.2Plotting..................................................................................................................................................119 6.2.1Procedureand Terminology ....................................................................................................119 6.2.2Report.....................................................................................................................................120 6.2.3 Current or Tidal Stream/Other Relations Between ‘O’, ‘A’ and ‘W’.........................................121 6.2.4Alteration by Observed Vessel ...............................................................................................122 6.2.5Alteration By Observing Vessel ..............................................................................................123 6.2.6Head Reach ............................................................................................................................123 6.3CollisionAvoidance...............................................................................................................................128 6.3.1Use of Trial Manoeuvre ..........................................................................................................132 6.4 Common Plotting Errors and Penalties (UK Examining Board)............................................................133 6.5Use for Navigation................................................................................................................................133 6.5.1Parallel Indexing .....................................................................................................................133 6.5.2Use of Nav Lines ....................................................................................................................137 6.5.3Precautions With Parallel Indexing .........................................................................................138 6.5.4Landfall...................................................................................................................................138 6.5.5Position Fixing........................................................................................................................139 6.6 Radar Detection and Interpretation.......................................................................................................139 6.6.1Characteristics of Propagation...............................................................................................140 6.6.2Reflective Properties..............................................................................................................140 6.6.3Interpretation ..........................................................................................................................140 6.6.4Icebergs and Ice Fields ..........................................................................................................141 6.6.5Unwanted Echoes ..................................................................................................................141 7 Extreme Weather and Navigation..................................................................................................................143 7.1 Tropical Revolving Storms (TRS) .........................................................................................................143 7.1.1Description..............................................................................................................................143 7.1.2 Shipboard Detection and Location of TRS .............................................................................145 7.1.3Actions on Board Vessel .........................................................................................................147 7.1.4Avoiding Actions .....................................................................................................................150 7.1.5Bridge Procedures – Summary..............................................................................................157 7.2 Planning for and Information on Ice ......................................................................................................158 7.2.1Sources of Information ...........................................................................................................158 7.2.2Readiness of the Vessel .........................................................................................................161 7.3Navigation in Ice Areas .........................................................................................................................162 7.3.1Master’s Duties .......................................................................................................................162 7.3.2 Effects of Ice and Snow Presence on Navigation ...................................................................162 7.3.3Signs of Drift Ice .....................................................................................................................164 7.3.4Signs of Open Water ..............................................................................................................164 7.3.5Icebergs ..................................................................................................................................164 7.3.6Ice Accretion ...........................................................................................................................165 7.4Operating in Ice....................................................................................................................................165 7.4.1 Factors to be Considered Before Entering Ice .......................................................................165 7.4.2Ship Handling in or Near Ice ...................................................................................................165 7.5Working with Ice Breakers ....................................................................................................................166 7.5.1Working in Convoys ................................................................................................................166 7.6Navigation in High Latitudes .................................................................................................................167 7.6.1Conceptof Time .....................................................................................................................167 7.6.2Charts and Bearings...............................................................................................................167 7.6.3Meridians and Parallels ..........................................................................................................167 7.6.4Dead Reckoning (DR)............................................................................................................167 7.6.5Use of Compasses.................................................................................................................167 7.6.6Electronic and Radio Aids .......................................................................................................167 7.6.7Celestial Navigation ................................................................................................................167 8Celestial Navigation........................................................................................................................................169 8.1The Celestial Sphere ............................................................................................................................169 8.1.1Celestial Co-Ordinates...........................................................................................................169 xii Navigation Advanced Mates/Masters 8.2Horizonsand Altitudes ..........................................................................................................................170 8.3Meridian Passage.................................................................................................................................171 8.3.1 Time of Observation for Meridian Passage............................................................................172 8.4Azimuthsand Amplitudes .....................................................................................................................172 8.4.1Azimuth...................................................................................................................................172 8.4.2Amplitude................................................................................................................................173 8.5Astronomical Position Lines..................................................................................................................173 8.5.1NavigationalTriangle ..............................................................................................................173 8.6Fix by Celestial Observations...............................................................................................................176 8.6.1Planning Sights .......................................................................................................................176 8.6.2Sights in Hazy Conditions .......................................................................................................177 8.6.3Abnormal Refraction...............................................................................................................177 8.6.4Plotting Sights .........................................................................................................................178 8.6.5 Errors in Astronomical Position Lines .....................................................................................182 8.6.6Cocked Hat.............................................................................................................................182 8.6.7 Polaris.....................................................................................................................................184 8.6.8SightReduction Tables ...........................................................................................................185 8.7NAVPAC...............................................................................................................................................187 9ElectronicNavigation Aids.............................................................................................................................189 9.1Satellite Navigation Systems ................................................................................................................189 9.1.1Global Positioning System (GPS)...........................................................................................189 9.1.2GLONASS ..............................................................................................................................190 9.1.3Galileo....................................................................................................................................190 9.1.4Beidou Satellite Navigation System ........................................................................................191 9.1.5Satellite System Comparison .................................................................................................191 9.1.6Differential GPS ......................................................................................................................191 9.1.7 Combined System – GNSS 1 (Global Navigation Satellite System) ......................................192 9.1.8Augmentation Systems...........................................................................................................192 9.1.9Comparison of DGPS and SBAS...........................................................................................193 9.1.10 FactorsAffecting Satellite Derived Positions..........................................................................193 9.1.11Precautions for Navigation.....................................................................................................194 9.1.12Satellite System Vulnerabilities ...............................................................................................195 9.2Hyperbolic Systems..............................................................................................................................195 9.2.1 LORAN-C (Long Range Navigation system) ..........................................................................195 9.2.2Eurofix.....................................................................................................................................198 9.3Echo Sounder.......................................................................................................................................198 9.3.1False Echoes ..........................................................................................................................198 9.3.2Usability..................................................................................................................................199 10Tides and Tidal Streams.................................................................................................................................201 10.1Causesof Tides....................................................................................................................................201 10.2Variation in Tides..................................................................................................................................202 10.2.1 Rotation of the Earth ...............................................................................................................202 10.2.2 Declination of the Moon..........................................................................................................202 10.2.3 Distance of the Moon ..............................................................................................................202 10.2.4 Earth-Sun System ..................................................................................................................203 10.2.5 Spring Tides ............................................................................................................................203 10.2.6 Neap Tides .............................................................................................................................203 10.2.7 Priming and Lagging ...............................................................................................................203 10.2.8 Land Effect ..............................................................................................................................203 10.2.9 Distance from the Pacific Ocean ............................................................................................203 10.2.10 Meteorological Conditions ......................................................................................................204 10.3Tidal Definitions....................................................................................................................................204 10.4 Underkeel Clearance and Air Draught ..................................................................................................205 10.5Tidal Calculations.................................................................................................................................206 10.5.1 EuropeanTides – Standard Port............................................................................................206 10.5.2 EuropeanTides – Secondary Port ..........................................................................................207 10.5.3 PacificTides – Standard Port .................................................................................................209 10.5.4 PacificTides – Secondary Port...............................................................................................210 10.5.5 Tidal Window on Passage ......................................................................................................211 Contents xiii 10.5.6 Offshore Tides ........................................................................................................................212 10.5.7 Tide Computations..................................................................................................................213 10.5.8 Neaping Situations.................................................................................................................213 10.6Tidal Streams........................................................................................................................................214 10.6.1 Rotary Streams .......................................................................................................................214 10.6.2 Rectilinear Streams ................................................................................................................215 10.6.3 Tidal Stream Data ...................................................................................................................215 10.6.4 Harmonic Constants ...............................................................................................................216 10.6.5 Use of Software ......................................................................................................................216 11Marine Communications................................................................................................................................219 11.1GMDSS .................................................................................................................................................219 11.1.1 INMARSAT.............................................................................................................................220 11.1.2 Digital Selective Calling (DSC) ...............................................................................................221 11.1.3SART......................................................................................................................................222 11.1.4 Enhanced Group Calling (EGC) .............................................................................................224 11.1.5 Maritime Safety Information (MSI) ..........................................................................................224 11.1.6 Components of GMDSS .........................................................................................................227 11.1.7 Carriage Requirements for GMDSS .......................................................................................227 11.2WWNWS ...............................................................................................................................................227 11.2.1 NAVAREA Warnings ...............................................................................................................228 11.2.2 Coastal Warnings...................................................................................................................228 11.2.3 Local Warnings .......................................................................................................................228 11.3Weather Reports...................................................................................................................................228 11.4Ship Reporting Systems .......................................................................................................................229 11.4.1 AMVER Organisation.............................................................................................................229 11.4.2 AUSREP.................................................................................................................................230 11.5 Ship Movement Report Systems ..........................................................................................................231 11.5.1 MAREP...................................................................................................................................231 11.5.2 SURNAV .................................................................................................................................232 11.6RadioMedical Advice ...........................................................................................................................232 11.6.1 International Radio Medical Centre(C.I.R.M.)........................................................................232 11.7Other Reports .......................................................................................................................................232 11.8 Automatic Identification System (AIS) ..................................................................................................232 11.8.1 Carriage Requirements ..........................................................................................................233 11.8.2 Equipment..............................................................................................................................233 11.8.3 Operating Principle .................................................................................................................233 11.8.4 Operating Modes ....................................................................................................................234 11.8.5 AIS Data Messages ................................................................................................................234 11.8.6 Additional Messages ..............................................................................................................235 11.8.7 AIS Types...............................................................................................................................235 11.8.8 Data Entry ...............................................................................................................................235 11.8.9 Display of AIS Information ......................................................................................................235 11.8.10 Graphic/Radar Display...........................................................................................................236 11.8.11 National Arrangements ...........................................................................................................237 11.8.12 International Arrangements ....................................................................................................237 11.8.13 AIS and Collision Avoidance ...................................................................................................237 11.8.14 Issues with AIS .......................................................................................................................238 11.9 Long Range Information and Tracking (LRIT) ......................................................................................238 12Search and Rescue at Sea.............................................................................................................................241 12.1 Search and Rescue Co-Ordination .......................................................................................................241 12.1.1 On-Scene Co-Ordination ........................................................................................................241 12.2 Search and Rescue Communications ..................................................................................................242 12.2.1 Initial Communications...........................................................................................................242 12.2.2 Information on Distressed Unit ...............................................................................................243 12.2.3 Information on Other Units .....................................................................................................243 12.3On board Preparation ...........................................................................................................................244 12.4Search Planning...................................................................................................................................244 12.4.1 Datum.....................................................................................................................................245 12.4.2 Search Area ............................................................................................................................246 xiv Navigation Advanced Mates/Masters 12.4.3 Search Patterns ......................................................................................................................247 12.4.4 Practical Application...............................................................................................................248 12.4.5 Records..................................................................................................................................250 12.4.6 Radar Use ..............................................................................................................................250 12.4.7 Aircraft Assistance ..................................................................................................................250 12.4.8 Conclusion of the Search .......................................................................................................250 12.5Rendezvous..........................................................................................................................................251 12.5.1 Plotting Method .......................................................................................................................251 12.5.2 Effect of Wind and Current .....................................................................................................254 12.5.3 Rendezvous Involving Change of Course/Speed ...................................................................255 12.5.4 Station Keeping ......................................................................................................................256 12.5.5 Rendezvous at a Specific Time ..............................................................................................260 12.6Interception...........................................................................................................................................264 12.7Rescue by Helicopter............................................................................................................................266 12.7.1 Onboard Preparations ............................................................................................................266 12.7.2 Evacuation..............................................................................................................................266 12.7.3 Hi-Line Technique ...................................................................................................................267 12.8 Search and Rescue Co-Operation Plans Aboard Passenger Ships .....................................................268 12.9Man Overboard.....................................................................................................................................269 12.9.1 In Open Waters .......................................................................................................................269 12.9.2 In Port.....................................................................................................................................269 12.9.3 Man Overboard Manoeuvres ..................................................................................................270 13 Offshore Installations and Navigation..........................................................................................................273 13.1 Offshore Oil and Gas Installations ........................................................................................................273 13.1.1 Rigs.........................................................................................................................................273 13.1.2 Wells .......................................................................................................................................274 13.1.3 Platforms.................................................................................................................................274 13.1.4 Mooring Systems (Single Point Moorings - SPM)..................................................................275 13.1.5 Submarine Pipelines ...............................................................................................................277 13.1.6 Navigation in Offshore Areas ..................................................................................................277 13.2 Offshore Renewable Energy Installations (OREI) ................................................................................278 13.2.1 Offshore Wind Farms ..............................................................................................................278 13.3 Offshore Wave and Tidal Energy Installations......................................................................................281 13.3.1 Wave Energy Convertors (WECs) ..........................................................................................281 13.3.2 Tidal Energy Convertors (TECs) .............................................................................................281 13.4 Visibility and Marking of Wave and Tidal Energy Installations ..............................................................282 14ECDIS and IBS.................................................................................................................................................283 14.1ECDIS...................................................................................................................................................283 14.1.1 Requirements.........................................................................................................................283 14.1.2 Use of ECDIS .........................................................................................................................286 14.1.3 Updating Electronic Charts.....................................................................................................291 14.1.4 Precautions During the Use of ECDIS ....................................................................................292 14.2Integrated Bridge Systems ...................................................................................................................295 Further Exercises...................................................................................................................................................297 Answers...................................................................................................................................................................299 Almanac Data..........................................................................................................................................................301 Glossary of Abbreviations.....................................................................................................................................367 References..............................................................................................................................................................370 Bibliography............................................................................................................................................................370 Index........................................................................................................................................................................371 Templates................................................................................................................................................................379 Radar Plotting Sheet..............................................................................................................................................380 Appendix.................................................................................................................................................................385 42 Navigation Advanced Mates/Masters 2.5.2.2 Clearing Marks Left (Northern) edge of island open to left of N Cardinal Buoy - ship in safety 30R 10 20 20 98 8 14 15 17 14 16 9 8 8 17 16 17 1813 12 11 2224 27 29 28 25 27 24 25 26 282927 262722 M S M S Sh M S Sh M S Pb S Pb 122 White White Red Red BY VQkFl 000350340 330 320 310 300 010020 030 040 050 060 101º T WO 145º T Figure 2.9 Use of clearing mark The ship’s safe approach can be monitored where two marks are used in conjunction. Once a safe bearing has been determined, the furthest of the selected marks should remain open to the side that the ship lies. In Figure 2.9, the ship will be safe if the island remains open to left of the North Cardinal buoy. 2.5.2.3 Horizontal Danger Angle Once the safe distance from a hazard has been determined, ie 7 cables, mark the chart with the safe distance to pass. Then determine the horizontal angle between two fixed objects that, by preference, should be the same distance either side of the hazard. In Figure 2.10, the safe distance is 81°. If the angle measured at the ship is equal to or less than the danger angle, the vessel will remain in safety. Where there are hazards either side of the track, repeat the same procedure for a point the same distance inside of the other hazard. In Figure 2.10 this is 50°. In this case, if the angle is more than 50°, the ship will remain in safety. NMT81° 81° 7 Cables NLT 50° Ship in safety if angle NLT50 or NMT 81 Hazard 1 Hazard 2 Figure 2.10 Horizontal danger angle Passage Planning 43 If the angle at the ship is no less than (NLT) 50° or no more than (NMT) 81°, the ship will remain in safety. 2.5.2.4 Horizontal Angle Fix In Figure 2.11: C Brg 1= 048° C Difference between 1 and 2= 47° C Brg 2= 095° C Difference between 2 and 3= 39° C Brg 3= 134° C Complement 1-2 = 90° - 47°= 43° Complement 2-3 = 90° - 39° = 51° The Horizontal Angle can be used for fixing. In this case, objects should be selected so that they and the ship do not end up on the perimeter of a circle. This is because the position can be plotted anywhere on the circle. To avoid this problem, objects should be on a straight line. Using the complements, two position circles are plotted. The fix can be used to determine the error in compass, as the fix is not based on the bearings themselves but on the difference of angle between the pairs. Compass error 1 = 048° C ~ 050° T = 2° E Compass error 2 = 095° C ~ 097° T = 2° E Compass error 3 = 134° C ~ 136° T = 2° E Fix 1 2 3 Centre 1-2 Centre 2-3 43º 51º Position circle 1-2 Position circle 2-3 Truebearing1 Truebearing2 Truebearing3 Figure 2.11 Fix using horizontal angle If the incorrect bearings have been plotted directly, use the format station pointer to obtain the correct fix. The true bearings can then be read from the chart. In both the cases, the cocked hat in terrestrial fixes can be resolved. 2.5.2.5 Sector Lights Sectors of coloured lights can be used to indicate the presence of navigational hazards and the safe water around them. These lights show different colours when viewed from different bearings. The limits of the sectors are marked on navigational charts. This method of monitoring can only be used in good visibility. 127° 083° 050° Red Red Red White White DangerSector Danger Sector Safe Sector 098° Danger Sector Safe Sector Figure 2.12 Use of coloured sectors 2.5.2.6 Clearing Bearings In the vicinity of hazards, the clearing bearings of selected objects should be determined and marked on the chart during planning to set the safety margins and for monitoring. These bearings should be determined as Not More Than (NMT) or Not Less Than (NLT). 44 Navigation Advanced Mates/Masters Clearing Bearing NLT 081° T Clearing Bearing NMT 100° T Bearing 078° T Ship in danger Bearing 089° T Ship in safety Selected Object 105°Tis more than 100º T 078° T is less than 081° T Bearing 105° T Ship in danger Figure 2.13 Explanation of use of clearing bearings 2.5.2.7 Leading Lights/Marks The principle is to keep the marks or lights in transit. •If the nearer mark is opening to starboard, the ship is to the left of the intended track•if the nearer mark is opening to port, the ship is to the right of the intended track. This method of monitoring can only be used in good visibility. Ship on leads Ship to right of intended trac k Ship to left of intended track Leading lights 044° Nearer light open to starboard Nearer light open to por t Figure 2.14 Use of leading lights 2.5.3Ship’s Profile and Datum Shift The position plotted on the chart represents a part of the bridge or the scanner’s position. Some parts of the ship are away from this point. Depending on the scale of the chart being used and the size of ship, these points may be in or approaching danger. It is important to know the corresponding size of the ship for the respective chart so the navigator is never in doubt about a hazard’s proximity and the time or distance to it. Simple cardboard models of the profile and shift for the different charts to be used during the passage can be a valuable addition to the chart table. Natural scale, dimensions of the chart and correction for datum should be used to calculate this. The models cannot be used on a smaller-scale chart as the vessel’s profile would be too small. Natural scale 1:12,500 at latitude 21° 30´ N Dimensions 965 mm × 635 mm (d.lat = 0° 5´.21) [ie 1 nm = 185.2 mm] Corrections for datum 0´.17 N, 0´.06 E Ship’s profile (for L = 300 m × B = 50 m) is 30 mm × 5 mm Datum shift is 019°T × 33.4 mm (0´.18) In electronic charts, the ship’s profile can be automatically generated for the scale in use. Depending on the navigation system being used and the datum of the chart, there may be a discrepancy Passage Planning 45 between the plotted position and the actual position, ie if it is not corrected before plotting. It is better to apply datum shift separately as the ship may not always be on the same heading as when the profile and shift model was prepared. 2.5.4Non-Visual Monitoring Techniques Using continuous monitoring techniques does not relieve the OOW from plotting the ship’s positions at the planned fix frequency. Parallel indexing, maps and navigation lines are used on radar for continuous monitoring. This is explained in detail in sections 6.5.1, 6.5.2 and 6.5.3. Terrestrial radio and satellite navigation systems can be used for continuous monitoring through use of cross track error and alarm, arrival alarm and course to steer alarm. Reliance on continuous monitoring systems must remain within the limitations of the base system in use. If the positioning system has an error of 0´.5, the monitoring may be constantly in error. Use of XTE on GPS etc, allows monitoring of ground track and speed made good against ship’s course and speed. It is also useful to monitor DR and EP. 2.5.4.1 Discrepancy in Positions If there are random errors, generally the position plotted from terrestrial observations will result in a cocked- hat, the intersection of the position lines closest to the hazard should be selected as the ship’s position. If there is a discrepancy in positions that have been plotted based on different systems, the above principle should still be put to practice. However, the mariner must carefully analyse the situation and should take into account the circumstances and reasons for the possible discrepancy before accepting a position. The situation could be of particular concern when hazards are approached in the open sea/ocean. For example, if a ship is to pass an isolated set of rocks, small island or shoal in open sea but positions have been obtained that place her in different locations. Generally, the position that is nearest to the hazard should be assumed and avoiding action should be taken. In Figure 2.16, the ship is required to pass the isolated rock with the lighthouse at 12 nm. It is assumed that the three positions have been plotted using Radar, GPS and Stellar Observations at twilight. Full analysis should be completed: •If star sight is correct, the ship is approximately 10nm South of the intended track. If stars are selected carefully and sight is taken correctly, then the position error should not be more than 1 to 2 nm•the GPS position puts the ship on track, although there should be no selective availability, there is no assurance that the system is functioning correctly•the Radar generated position is a single range and bearing. This puts the ship about 4 nm South of the intended track. In addition, the radar range may be accurate but bearing may not be. Also the radar range of light is 23nm. This may cause doubt as the range and bearing could have been from another passing ship. As the bearing is not a visual bearing doubt exists•the only position described above that is based on visual identification is Star Sight. Profiles of Ship of Length 300 m and Beam 50 m Scale meters 010.52 For chart with vertical dimensions 965 mm covering d.lat 5'.21 Different Headings of the Ship. (Note no change in Datum Shift for same chart) Figure 2.15 Profile and datum shift 46 Navigation Advanced Mates/Masters 100 30R2530 3450 3317 3215 3590 2680468 416 917 2917 281° T 3225 Stellar Position Radar Position: Range 23 nm, Brg 258 T GPS Position 300 310 320 330 340 350000010020 030 040 050 060 Figure 2.16 Profile and datum shift In this situation, the ship should immediately alter course to NW or NNW. While the ship cannot obtain soundings at its current position, the echo sounder should be switched on to obtain a warning when the depth is less than 500m. On the radar the parallel indexing should be set up on the lighthouse. GPS positions should also be plotted regularly to identify the trend in the track being made and the set being experienced. If night is approaching, lookouts should focus on detecting lights, in daylight they should be attempting to visually detect the lighthouse. 2.6Summary WatersCongestedCoastalOpen VisibilityGoodPoorGoodPoorGoodPoor VisualPP Continuous visual monitoring techniques PP Parallel Indexing/ Electronic monitoring SPSP RadarSPSP LORAN CSSSS DGPSSP/S GPSSPP CelestialS Table 2.4 Primary and secondary position fixing/monitoring methods Author’s Note: The operation of a ship is a complex task. The navigation officers and Master are required to perform a number of tasks simultaneously. The environment can be hostile. The legal requirements surrounding shipping are very stringent. Any error or omission can result in a disaster. With high costs, public and environment damage liability bills increasing all the time, the mariner and the ship operators must ensure that ships are operated as safely as possible. Effective voyage planning is only one of the steps towards ensuring the safety of operations. 4747 Basic mathematics is used to determine the course, distance and other relevant details of the passage between two points on the surface of the earth. Some methods use plane trigonometry, while others use spherical trigonometry. Before moving on to actual principles and calculations involving sailings, it is useful to identify and explain some of the relevant terms. 3.1The Terrestrial Sphere Spherical trigonome