Ship Passage Planning



VOYAGE PLANNING - GUIDANCE NOTES

1. General

Investigations show that human error contributes to 80% of navigational accidents and that in many cases essential information that could have prevented the accident was available to but not used by those responsible for the navigation of the vessels concerned. Most accidents happen because of simple mistakes in use of navigational equipment and interpretation of the available information, rather than because of any deficiency in basic navigational skills or ability to use equipment.

Masters, skippers and watchkeepers should therefore adhere to the IMO Guidelines taking the following measures to ensure that they appreciate and reduce the risks to which they are exposed:

    a) ensure that all the vessel's navigation is planned in adequate detail with contingency plans where appropriate
    b) ensure that there is a systematic bridge organisation that provides for:
      (i) comprehensive briefing of all concerned with the navigation of the vessel;
      (ii) close and continuous monitoring of the vessel's position ensuring as far as possible that different methods of determining the position are used to check against error in any one system
      (iii) cross-checking of individual human decisions so that errors can be detected and corrected as early as possible
      (iv) information available from plots of other traffic is used carefully to ensure against over-confidence, bearing in mind that other vessels may alter course and/or speed
    c) ensure that optimum and systematic use is made of all appropriate information that becomes available to the navigational staff;
    d) ensuring that the intentions of a pilot are fully understood and acceptable to the vessel's navigational staff

2. Responsibility for Voyage planning

In most deep-sea vessels the master delegates the initial responsibility for preparing the plan for a voyage to the officer responsible for navigational equipment and publications (hereafter referred to as the navigating officer.) On smaller vessels, including fishing vessels, the master or skipper may have the responsibility of the navigating officer for voyage planning purposes. Prior to departure the navigating officer will prepare the detailed voyage plan from berth to berth in accordance with the Guidelines and to the master's requirements. If the port of destination is not known or is subsequently altered, the navigating officer must extend or amend the original plan as appropriate.

3. Principles of Voyage planning

The four stages of Appraisal, Planning, Execution and Monitoring logically follow each other. An appraisal of all information available must be made before detailed plans can be drawn up and a plan must be in existence before tactics for its execution can be decided upon. Once the plan and the manner in which it is to be executed have been decided, monitoring must be carried out to ensure that the plan is followed.

Appraisal is the process of gathering all information relevant to the proposed voyage, including ascertaining risks and assessing its critical areas. The Guidelines list the items that should be taken into account.

An overall assessment of the intended voyage should be made by the master, in consultation with the navigating officer and other deck officers who will be involved, after all relevant information has been gathered. This appraisal will provide the master and his bridge team with a clear and precise indication of all areas of danger, and delineate the areas in which it will be possible to navigate safely taking into account the calculated draught of the vessel and planned under-keel clearance. Bearing in mind the condition of the vessel, her equipment and any other circumstances, a balanced judgement of the margins of safety which must be allowed in the various sections of the intended voyage can now be made, agreed and understood by all concerned.

Once a full appraisal has been carried out the navigating officer carries out the Planning process, acting on the master's instructions. The detailed plan should cover the whole voyage from berth to berth, and include all waters where a pilot will be on board. The plan should be completed and include all the relevant factors listed in the Guidelines.

The appropriate charts should be marked clearly showing all areas of danger and the intended track taking into account the margins of allowable error. Where appropriate, due regard should be paid to the need for advanced warning to be given on one chart of the existence of a navigational hazard immediately on transfer to the next. The planned track should be plotted to clear hazards at as safe a distance as circumstances allow. A longer route should always be accepted in preference to a shorter more hazardous route. The possibility of main engine or steering gear breakdown at a critical moment must not be overlooked.

Additional information which should be marked on the charts include:

If an electronic chart system is used to assist voyage planning the plan should also be drawn up on the paper charts. Where official (ENC) vector data is available an ECDIS provided with fully compliant ENC data for the vessel's voyage may be used instead of paper charts. Raster Chart Display Systems (RCDS) using official and up to date Raster charts can be used in conjunction with paper charts to assist voyage planning and route monitoring. Hazards should be marked on the RCDS as well as on the paper chart. Systems that use unofficial chart data should not be used for voyage planning or navigation.

Depending on circumstances, the main details of the plan should be marked in appropriate and prominent places on the charts to be used during the voyage. They should also be programmed and stored electronically on an ECDIS or RCDS where fitted. The main details of the voyage plan should also be recorded in a bridge notebook used specially for this purpose to allow reference to details of the plan at the conning position without the need to consult the chart. Supporting information relative to the voyage, such as times of high and low water, or of sunrise or sunset, should also be recorded in this notebook.

It is unlikely that every detail of a voyage will have been anticipated, particularly in pilotage waters. Much of what will have been planned may have to be adjusted or changed after embarking the pilot. This in no way detracts from the real value of the plan, which is to mark out in advance, areas where the vessel must not go and the appropriate precautions which must be taken, and to give initial warning that the vessel is standing into danger.

Execution of the finalised the voyage plan should be carried out taking into account the factors listed in the Guidelines. The Master should take into account any special circumstances which may arise, such as changes in weather, which may require the plan to be reviewed or altered.

Monitoring of the vessel's progress along the pre-planned track is a continuous process. The officer of the watch, whenever in any doubt as to the position of the vessel or the manner in which the voyage is proceeding, should immediately call the master and, if necessary, take appropriate action for the safety of the vessel.

The performance of navigational equipment should be checked prior to sailing, prior to entering restricted or hazardous waters and at regular and frequent intervals at other times throughout the voyage.

Advantage should be taken of all the navigational equipment with which the vessel is fitted for position monitoring, bearing in mind the following points:

    (a) positions obtained by electronic positioning systems must be checked regularly by visual bearings and transits whenever available;
    (b) visual fixes should, if possible, be based on at least three position lines;
    (c) transit marks, clearing bearings and clearing ranges (radar) can be of great assistance;
    (d) it is dangerous to rely solely on the output from a single positioning system;
    (e) the echo sounder provides a valuable check of depth at the plotted position;
    (f) buoys should not be used for position fixing but may be used for guidance when shore marks are difficult to distinguish visually; in these circumstances their positions should first be checked by other means;
    (g) the charted positions of offshore installations should be checked against the most recent navigational notices;
    (h) the functioning and correct reading of the instruments used should be checked;
    (i) account must be taken of any system errors and the predicted accuracy of positions displayed by electronic position fixing systems; and
    (j) the frequency at which the position is to be fixed should be determined for each section of the voyage.

Each time the vessel's position is fixed and marked on the chart in use, the estimated position at a convenient interval of time in advance should be projected and plotted. With ECDIS or RCDS care should be taken to ensure that the display shows sufficient "look-ahead" distance and that the next chart can be readily accessed.

Radar can be used to advantage in monitoring the position of the vessel by the use of parallel indexing, which is a simple and most effective way of continuously monitoring that a vessel is maintaining its track in restricted coastal waters. Parallel indexing can be used in any situation where a radar-conspicuous navigation mark is available and it is practicable to monitor continuously the vessel's position relative to such an object. It also serves as a valuable check on the vessel's progress when using an electronic chart.


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