Chapter 5 - MONITORING THE SHIPs PROGRESS Flashcards
Importance of Monitoring the ships progress
Monitoring is ensuring that the ship is following the pre-determine passage plan and is a primary function of the Officer of the Watch
Fixing Method
The first requirement of monitoring is to establish the position of the ship. Thiss may be done by a variety of methods, ranging from the very basic three bearing lines, through a more technically sophisticated use of radar ranges and bearings, to instant readout of one of the electronic position fixing systems, e.g., LORAN or GPS. The result though, is always the same. However the fix has been derived the OOW finishes up with no more than a position. It is how this information is used that is important.
Visual Bearings
As stated above, fixing methods vary. Basic fixing consists of
taking more than one position line obtained from bearings using an
azimuth ring on a compass. Gyro or magnetic, the bearings are
corrected to true, drawn on the chart and the position shown. Three
position lines are the minimum required to ensure accuracy.
Poor visibility or lack of definable visual objects may prevent a three bearing fix being made. In this case radar derived ranges (distances) may be included in the fix and under some circumstances make up the whole of the fix. In any case a mixture of visual or radar bearings and radar ranges is acceptable. Other methods may be used, e.g. running fixes (which may be inaccurate as they depend on an clement of DR) sextant angles etc, but these are seldom used on modem ships. Any good chartwork textbook will give a wide range of less used fixing methods.
Electronic position fixing may also be used, particularly where there are no shore-based objects to be observed and the radar coastline is indistinct. Whilst these systems appear to be infallible the operator needs to have a good understanding of the principles and failings of the electronic system being used, in order to avoid a false sense of security.
Fix frequency will have been determined at the planning stage. Even so, this may have to be revised, always bearing in mind the minimum frequency required is such that the ship cannot get into danger between fixes.
Regularity
Fixing needs not only to be accurate and sufficiently frequent it also needs to be regular.
Estimated Position
Regular fixing also allows a fix to be additionally checked. Each time a position has been fixed, it is good practice to estimate the position that the ship will have reached at the next fix. Providing fixing is being carried out at regular intervals this can easily be picked off as the distance between the present and the previous fix and checked against the anticipated speed. If the next fix coincides with the Estimated Position (EP) then this acts as an additional check that the ship is maintaining its track and speed. Should the fix not coincide with the EP then the OOW is aware that something is either wrong with the obtained position or some external influence has affected
the ship. The first action is to check the EP, then check the fix. If they are both correct then something is influencing the ship; either the course being steered is not the one required or the engine revolutions have changed. If both these features are in order then some external influence is affecting the ship, either the wind has changed direction or strength or the tidal stream has changed. The OOW is immediately aware that something is influencing the ship and can take immediate action to correct it.
Soundings
It is also good practice to observe the echo sounder at the same time as fixing and writing this reading on the chart beside the fix. If the observed reading is not the same as that expected from the chart then the OOW is immediately aware that something is not right. It may be that the chart is wrong, it may be that the ship is standing into danger.
Cross Track Error
Having fIXed the position the OOW will be aware of whether or not the ship is following the planned track and whether or not the ship will arrive at the next waypoint at the expected time. If the ship is deviating from the planned track the navigator must determine whether or not such deviation will cause the ship to stand into danger and what action he should take to remedy the situation. Apart from deviating from track to avoid an unplanned hazard such as an approaching ship, there is seldom justification to not correct the deviation and get the ship back onto the planned track. The OOW must use his judgement as to how much he needs to alter course to return to track. He must also bear in mind that even when he has returned to the planned track he may need to leave some of the course correction on in order to compensate the cause of the earlier
deviation.
International Regulations for the Prevention of Collisions at Sea
Irrespective of the planned passage, no ship can avoid confonning with the requirements of the Rule of the Road. These Rules are quite clear, are internationally accepted and understood by most OOWs.
RULE 16 states “Every vessel which is required to keep out of
the way of another shall, so far as possible, take early and substantial action to keep clear.”
Despite the requirement to maintain rrack, RULE 8 makes it quite clear that the give way ship must keep clear, either by altering course or if this is impossible then by reducing speed, or a combination of both these factors. Proper planning will have ensured that the ship will never be in a situation where such action cannot be taken.
In areas of heavy traffic and proximity of dangers, the person having the con will have to hold a delicate balance between planned track maintenance and other ship avoidance. The priority will be to avoid collision, but not at the expense of grounding.
Non-navigational emergencies
Similarly, the bridge team must never allow the reaction to an emergency situation to so dominate their response that the ship is put into a hazardous situation such as aCcidentally entering an area of high danger. Again, the planning should have allowed for such contingencies but even the best plan cannot allow for every conceivable situation. Situational awareness and careful assessment of the changing circumstances, coupled with principles of bridge team management will help prevent a bad situation compounding and becoming worse.
Time Management
In the event that the ship is ahead of or behind the planned ETA at the next waypoint, the OOW must use his judgement as to whether he adjusts the speed or not. In some instances, as for example when it is imperative that the ship’s ETA is critical to make a tide, then ETAs have to be adhered to.
In either of the instances cited above, it will be the observance of night or standing orders or at the OOW’s discretion as to whether he advises the master.
Lookout
The OOW’s situational awareness will be improved by both the structured management of the team and his own seU-discipline ensuring that he keeps a good professional watch. This will indude his confirming that a good lookout is kept. A good lookout does not just mean that he personally keeps a good visual lookout of the ship’s surroundings.
Rule 5 of the International Regulations for the Prevention of Collisions at Sea (1972, ratified 1977) states:
“Every vessel shall at all times maintain a proper look out by sight and hearing as well as by all available means appropriate in the prevailing conditions so as to make a full appraisal of the situation and of the risk of collision.”
Though specifically addressing collision the above quoted rule also applies if the OOW is to maintain his situational awareness. The keeping of an efficient look out needs to be interpreted in its fullest sense and the OOW needs to be aware that look out includes the following items:
1 A constant and continuous all round visual look out enabling a full understanding of the situation and the proximity of dangers, other ships and navigation marks to be maintained. In some instances, particularly in poor visibility, radar will give a better picture of the ship’s environment than actual visual observation. However, unless the OOW has considerable experience of comparing the radar picture with the visual scene he cannot automatically interpret his radar picture. In any case, the visual scene is the real scene not an electronic version of reality and the OOW who frequently
observes the scene outside the windows will have a better understanding of and feel for the world around him.
2 Visual observation will also give an instant update of environmental changes, particularly visibility and wind.
3 Visual observations of the compass (magnetic or gyro) bearing of an approaching ship will quickly show whether or not its bearing is changing and whether or not it needs to be considered a danger.
4 Visual observation of characteristics of lights and timing of them is the only way of positively identifying them and thus increases the OOW’s situational awareness.
5 Lookout will also include the routine monitoring of ship control and alarm systems, e.g. regularly comparing standard and gyrocompasses and that the correct course is being steered.
6 Electronic aids should not be overlooked or ignored under any circumstances, but it should be borne in mind that echo sounders, radars etc. are aids to navigation, not merely single means of navigation.
7 Also included in the concept of lookout should be the advantageous use of VHF. Judicious monitoring of the appropriate channels may allow the OOW to be aware of situations arising long before the ship is actually in the affected area.
8 A routine should be established for major course alterations including:
8.l Checking astern prior to altering.
8.2 Checking, both visually and by radar along the bearing of the new track.
The OOW’s situational awareness will also be enhanced by his observation of the environment using alI available means, not just limiting himself to the routine of fixing and correcting as described above.
Under-keel Clearance
Routine observation of the echo sounder needs to be one of the procedures of the watch.
Waypoints
Besides being points noted on the chart where a change of status or an event will occur, waypoints are also good indicators of whether the ship is on time or not If not, then something has occurred or is occurring that has affected the passage and the OOW will take steps to correct this occurrence.
Transits (Ranges)
Transits are often important navigational features; they can for example be used to cue decisions such as a wheel over, but can also be used in a more passive role. The OOW can use a transit to confirm that the ship is on schedule or that it is remaining on track, particularly when this occurs after an alteration. Of itself, the confirming transit may be no more than a minor occurrence but it will help the observant OOW confirm in his own mind that an is well and as it should be.
Leading Lines
Leading lines, i.e. the transit of two readily identifiable land based marks on the extension of the required ground track and usually shown on the chart are used to ensure that the ship is safely on the required track.
