Sailings Chart Work Exercises Information from Charts Tides Sextant


Terrestrial Navigation



Information from Charts


The Chart Catalogue

Many countries publish Chart Catalogues. Among the principal chart publishers is the Hydrographer to the Navy (U.K.). However other countries that do publish charts also make available data to the International Hydrographic Organisation, who allows different countries to publish these charts. Thus the 2nd publishers just print from whatever data they get from the IHO and the survey is conducted by the 1st country. These series are termed International series and bear the stamp of the IHO.

To give an example note the label on the following:

Here you see the surveying country as Singapore and the IHO emblem on the right of the emblem of Singapore.

The charts that are published anywhere follow the rules as laid down by the IHO, thus learning to use a chart of one country makes one proficient in using other charts.

The above picture is self explanatory if read in conjunction with the following picture:

Prior taking a new chart for use the following must be checked:

  1. The correction record at the bottom – left hand corner
  2. The year of publishing
  3. The scale of the chart, and
  4. The source table

The source table would give the type of survey that was carried out and when. Many charts are published with some areas being surveyed recently while in other areas the data is taken from previous surveys (which may be quite old).

All International series charts have the International number beside the national number of the chart.

Learning the symbols printed on the Charts:

While charts are published, the abbreviations, the symbols and the colour code is not mentioned on the charts and the mariner is expected to know of such things prior to using the charts.

The above symbols and the abbreviations are printed in another publication called Chart 5011 by the UK Hydrographic office. Other countries do have such books.

To give an example of a few items:

The above shows a compass rose. The circle is always projected in the above manner, the top of the rose pointing to the top of the chart.

The outer ring is the one from where the true bearings are plotted.

Within the outer ring there is an inner ring graduated in the same way but slightly off with reference with the outer ring. This inner ring is the one that has not been compensated with the variation.

Thus if the bearings that are plotted are corrected only for deviation then these may be drawn using this ring graduation.

The variation is again written on the north marking line – in this case is written as:

4°15’ W 1985 (6°E)

Meaning that in 1985 the variation at that place, where the rose is printed was 4°15’West and that the yearly change is 6°E. Now to get the variation for 2004, we have to multiply the number of years since 1985 – 19 years with 6° and get 114°. So 1°54’ have to be subtracted from 4°15’W. Subtract since the change was E.

Passage Planning

Passage Planning is a way of minimising the risk of navigational error.  In areas of high traffic density and restricted available water, the requirement for pre-planning becomes even more necessary.

The aim of passage planning is to prepare for the navigation of the ship so that the intended passage can be executed in a safe manner in respect of both the vessels and the protection of the environment, by ensuring the proper and positive control of the ship at all times.  Without such planning, the time to process essential information may not be available at critical times when the bridge team is occupied in confirming a landmark, altering course, avoiding or monitoring traffic and carrying out other bridge duties, such as external communications and internal communications within the ship.  Under these circumstances, unless there is an effective plan in place, mistakes and errors may go undetected leading to disastrous consequences.

The construction of an effective passage plan encourages all those concerned to foresee potential problems and plan a strategy to minimise the risk.

No specific courses are laid down as it is necessary for all vessels to plan, and lay down on the chart, their own course. 

Where alterations of course are required, the latitude or longitude or approximate bearing to a navigational mark, which ever is more appropriate, is used singly to indicate an obvious change of direction in the traffic separation scheme.  This to ensure that navigators are not using a set of advised, fixed positions thus avoiding vessels using exactly the same courses in their individually developed plans.


The Checklists are a basis for individual ships either amending or drawing up their own checklists.  They should not be considered to be definitive but the basis for individual ships to expand upon.  The checklists incorporate checks for readiness for transit and reporting. 

Parallel Indexing

This is the simplest and quickest pilotage technique that gives continuous monitoring of the track that the ship is making good.  Parallel indexes should be used, whenever practicable, while transiting through coastal areas.  To this end, for every leg, suggested reference points should be included into the Passage Notes.  These points are known to be radar conspicuous and likely to be available at all times.  Buoys, especially buoys known to be prone to damage or movement, should never be used.

Wheel Over Positions

Course alteration positions should be chosen to allow for proper monitoring during ship turns.  Ships using a plan would have their maneuvering characteristics and the ships data must thus be consulted when planning a wheel over position.

Where possible, techniques for monitoring the turn should be used.  This may be using a rate of turn indicator, parallel indexing or other suitable techniques.

Emergency / Contingency Plans

By preparing in advance for possible contingencies, a quick and effective response can be made when the unexpected happens.  Plans should be considered for coping with, amongst others, steering failure, power loss, loss of propulsion or any other type of accident or emergency that may occur on a ship that will affect the navigational ability.

To this end, the Passage Notes, for each leg, should indicate the available depth of water.  


The requirement for an effective plan is included in the STCW Convention that states - "The intended voyage shall be planned in advance taking into consideration all pertinent information and any course laid down should be checked before the voyage commences."


The purpose of passage planning is to ensure control over the safe navigation of the ship at all times.  This is normally achieved by entering onto the chart as much information as is available to enable immediate reference should the unexpected occur.  Also to monitor the progress of the vessel along the intended tracks and within previously planned and agreed parameters.

Information Required to Formulate a Passage Plan

Prior to compiling a passage plan as a minimum, the following publications will be required in addition to this guide:

chart catalogue

corrected navigational charts

routeing and pilot charts

IMO Ship's Routeing

sailing directions and pilot books

light lists

tide tables

tidal stream information

Navtex local warnings and Notices to Mariners (Navareas, Hydropacs) radio signal information (including VTS and pilot service) owner's and other unpublished sources manoeuvring data

Mariner's Handbook

climatic information and weather forecasts electronic navigational systems information (as applicable) personal experience of ships navigating officers.

Additionally, when compiling the passage plan the availability and reliability of the following have to be considered at the early part of the planning phase:

main propulsion system

steering gear

navigational equipment


thrusters (if equipped)


trim and draught of vessel

transverse stability

the availability of manpower.

Preparing the plan

When preparing the plan the navigating officer will need to take account of the following:

a.                   Adequate under keel clearance at all times, including allowances for squat, pitch, roll, swell, predicted tidal height and possible increase of draught due to heel and trim

b.                  safe distances off dangers, allowing for weather, tidal stream, anticipated traffic, availability of safe water and navigational systems in use

c.                   alter-course positions which can be monitored conveniently either visually or by radar

d.                  management of chart changes, which should not occur at critical points of the passage

e.                   The Traffic Separation Schemes, and the requirements of Rule 10

f.                    predicted tidal stream information, leading to the pre-working of allowances for set

g.                   visibility of lights (especially in the Malacca Straits), rising/dipping distances, arcs and colours of light sectors

h.                   envisaged safe speeds along the route, taking into consideration recommended area of reduced speed, leading to a speed plan for the transit, and an ETA plan at the pilot station or

i.                     storing position, making due allowance for possible reduced visibility. A plan for reducing speed under control should be considered

j.                    selection of depths for comparison with the echosounder, taking note of the predicted height of tide may be desirable for certain routes

k.                  reporting points, VHF frequencies, VTS requirements, areas of special concern and pilot station frequencies if either requiring a pilot or areas of increased traffic density.

l.                     abort positions for specific sections and contingency plans in case of accident or emergency or bad visibility

m.                 the primary and secondary systems of navigation to be used

n.                   requirements of any electronic chart systems

o.                  all charts and publications available are up to date

p.                  equipment status

q.                  margins of allowable error, safety clearing bearings and ranges

r.                    the making up of a bridge, or conning, notebook.

The master must satisfy himself that the passage plan meets all his requirements and he must then ensure that all watch-keeping officers are properly briefed; and that the plan is kept amended and upto-date for the intended passage.

Passage planning therefore should be a preparation for effective piloting by selecting, and marking in advance, those relevant navigational techniques which will lead to safe control of the ship and adherence to the plan.

Parallel Indexing

As mentioned previously this is the simplest and quickest pilotage technique, and is highly recommended as it gives continuous monitoring of the track that the ship is making good As with all radar techniques, parallel indexing should be practised in clear weather during straightforward passages so that personnel become thoroughly familiar with the technique before attempting to use it in confined or difficult passages, at night or in restricted visibility.  Great care should be taken in identifying and confirming reference points on the chart and on the radar; and also in verifying the radar range when using the parallel index.

Preparing the Chart

1 .The first step when preparing a passage plan is to identify and mark the 'no-go' areas on the chart.

The charts supplied to ships are the same for everyone, whether for use on board a VLCC at 25 metres draught or on a coaster sailing at 3 metres draught.  It is therefore imperative that the chart is made suitable for the specific condition of your vessel.  This should be done by marking the 'limiting danger lines' - often referred to as marking out the 'no-go areas.'

These are valuable safety limits to any plan for a coastal.  Lines must be drawn on the chart to highlight where the vessel cannot go.  Proper allowance must be made for maximum draft and predicted tidal height and any other limiting condition.  The concept of marking no-go areas has the following benefits:

a.                   it forces consideration of the factors affecting under keel clearance, which is always the high risk element

b.                  it forces a concentrated study of the chart, rather than just a glance it immediately highlights to anyone who looks at the chart the, often large, areas that must be avoided.

It is not enough to depend on, say, printed depth contour lines.  The lines have to be prominent in order to highlight the immediate danger quickly and effectively at any time under any light condition.

It is important to draw the no-go boundaries as accurately as possible.  They should show, for example, that the vessel can pass the wrong side of a mark, in an emergency, although this may not normally be desirable.  It can be seen from the study of some recent incidents that had this information been immediately available, then a grounding or collision would most probably not have occurred.  In this context passing the wrong side of a buoy is nothing compared with the consequences of even a minor incident.

Insert the 'limits of safety'.  Normally this will be an area either side of the vessels intended track that may be acceptable to deviate within, under normal circumstances.  In the approaches to ports as well as in some areas, however, this may be the traffic lanes already on the chart.  However in certain areas, additional lines should be marked on the chart to highlight where it has been considered that it is only safe to navigate under normal circumstances.

After these considerations have been made the vessels intended track should be inserted.

The wheel over positions should then be marked on the chart.  When marking the wheel over positions consideration should be given to the amount of rudder that will be applied, the expected speed of the ship at the alteration position and also the depth of water due to the effect on the turning circle of shallow water,

It is often valuable to insert the speed that is to be maintained along certain sections of a leg.  This is especially true if an accurate ETA is required at a certain point, e.g. for picking up pilots or rendezvousing for stores.

The methods to be used for fixing the vessels position on different parts of the intended track should be entered onto the chart.  The prime method should be by visual fix, whenever possible, backed by radar or electronic means.  If, from experience, it is known that there are conspicuous landmarks or points for position fixing it is often worthwhile to identify these.

The timing of fixing the vessels position should be considered when passing though the congested waters.  The requirement for fixing the vessels position will vary considerably, based on the nearness of the most imminent danger and also while executing and completing a turn.  As a back up to frequent fixing, the use of parallel indexing techniques will assist in ensuring the vessel is maintaining the intended track and should be considered, especially in the more constricted parts.

From experience it will become evident what identifiable marks are radar conspicuous.  It is of value to mark these radar conspicuous targets on the chart for future reference.  Weaker targets that may be usefully used in clear weather may disappear in heavy rain and thus may not be available.

Clearing bearings for hazards, and to assist in maintaining the track should be inserted onto the chart.  These give a very quick method of checking that the vessel is, at least, missing dangerous or noteworthy points.

Clearing ranges are another technique used by some vessels to ensure that a minimum and maximum distance is maintained from a identifiable mark.  These should be considered on all vessels where parallel indexing is not being employed and may especially beneficial when completing a turn.

Prior to entering a restricted section abort points should be entered on the chart.  At this point it must be agreed that to proceed any further all systems etc. have to be fully operational and the vessel is in readiness to proceed.  As well as entering the abort point on the chart it is often recommended that the action to be taken to abort is also entered onto the chart.  E.g. When reaching the abort point the engine speed is reduced and the direction of turn, with possibly the helm order, entered so that all personnel involved in navigating the vessel are fully aware of the agreed action to be taken.

In addition to the abort positions contingency planning should also take place whilst compiling the passage plan.  By marking the "no-go areas" on the chart, as suggested above, it should be readily apparent if there is sufficient water outside the traffic lanes in which to anchor.  By preparing in advance for possible contingencies, a quick and effective response can be made when the unexpected happens.  Plans should be considered for coping with, amongst other things, main engine failure, steering loss, port or channel closures, radar failure, reduction in visibility, heavy traffic at crucial points, movement or closure of a pilot station, or any of the accidents and emergencies that can occur to a ship on passage.

The tidal streams and heights at the time of expected transit should be marked on the chart.  The depth of water, in general, at sea should not pose a problem for vessels, but if the height of tide is marked on the chart, in coastal waters it will assist in contingency planning.  The direction and strength of the tide and current in certain parts, can be very strong and should be marked on the chart in prominent positions.  This will assist, not only, in predicting and understanding the movement of your own ship but also the movement of others, especially slow moving vessels and tugs with tows.

In addition to the above it is suggested that the reporting points are clearly marked on the chart, in addition to the positions where it is necessary to change VHF channels.

Also the position of expected high traffic density should be marked on the chart along with any other relevant information. 

Monitoring the Passage Plan

It is common practice to fix the ship's position and then make an allowance for set and drift depending upon offset from the previous fix.  This approach to navigation is REACTIVE, being based upon past observations.  If either of these is wrong, then any predictions using them will be erroneous.  When using fixes in this way, it is usually better to make the fixes at regular and appropriately frequent intervals.  This enables a simple check to be made with respect to speed.  It also helps the quick and effective calculation of short-term EPs (Estimated Positions), using the latest course and speed made good, to warn of any immediate problems developing.

However, in narrow and restricted waters, techniques need to be used which enable the navigator to maintain a forward outlook, that is to be PROACTIVE, whilst monitoring the deviation from the intended track being made good.  Frequent, hurried visits to the chart table to fix the vessel's position may not be the most effective use of the time available.  Also, whilst doing this the overall sense of awareness can be interrupted and it is easy, during critical phases, to become disorientated.

It is worth remembering to monitor the echo-sounder.  This instrument can often provide the first warning signs that the vessel is standing into danger, since in almost all situations the nearest land is beneath the vessel.



Are the charts the largest scale available?         

Are they corrected for the latest Notice to Mariners and local navigational warnings?

Do the charts completely cover the area?

Sailing Directions

Is the planned track following recommended routes?

 Is the plan following local regulations?

Are all potential hazards known?

Port / Storing Information

Are local conditions known?

Is berthing / storing information available?

Tidal Atlas/Tables

Have the stream strength and directions been discussed?

Have the tidal heights been discussed?

List of Radio Signals

Where is the pilot boarding area?

Are VHF Port working channels and     procedures noted?

Where are the required calling in points?

Weather Reports

Is the local forecast available?

Local Agent

Has the agent advised of berth and berthing/stores and storing requirements?

Vessel Condition Comments                        

What is the draft and air draft?             

What is the minimum acceptable underkeel clearance?

Manoeuvring Data

Have considerations for squat been made and are tables available?

Chart Information

No-go areas    

Margins of safety plotted

Plotted tracks

Have we calculated the wheel-over points and what are they?

Parallel index references

Required speed at differing way points

Tidal stream anticipated

Crew call out position

Tug meeting area

Abort positions

Contingency plans available?


Were all navigators present?

Have the fixing intervals been determined?        

Have fixing points been determined?

Have the primary navigation aids been determined?

Have the secondary means been discussed?

Have the areas of high risk been determined and discussed?

Has the bridge team discussed the information flow and has it been agreed?

Has the charted plan been discussed?   

Has the watch condition been    determined?

Have duties been assigned and understood?

Have the conditions for increasing the watch been determined?

Have team members been made aware of any defective equipment?



International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA)

The IALA buoyage system is split into 2 regions A and B. Region B is mostly areas of the world with American influence, Region A is mostly countries with United kingdom influence.

IALA Buoyage System ‘A’ and ‘B’

click for larger image

Visibility of Lights:

Lights are placed on Light Houses at a height of the light houses, depending on the intensity of the lights themselves, the lights are marked as visible up to a distance of a certain limit, the height of the observer when declaring the above is taken to be 15 feet (4.5 metres).

However the visibility of the lights at the marked limit may be exceeded due to the height of the ship also.

The expression for obtaining the raising of the light limit is given by:

Heights in feet:

Distance = (√Height of observer x 1.15) +  (√Height of Object x 1.15)

Heights in metres:

Distance = (√Height of observer x 2.083) +  (√Height of Object x 2.083)

Or Distance = (√Height of observer x 2.1) +  (√Height of Object x 2.1)


Assume the following:

Height of eye (Bridge): 21 m

Height of Light House (from List of Lights): 60 m Range: 20 NM

Then the above equation would be as follows:

Distance = (√Height of observer x 2.1) +  (√Height of Object x 2.1)

Distance = (√21 x 2.1) +  (√60 x 2.1)

Distance = (4.58 x 2.1) +  (7.75 x 2.1)

Distance = 25.9 NM

That is the light would be seen from a distance of 26 NM.