NV Ch. 5 — Monitoring the Ship's Progress

1. Introduction — what monitoring means

Monitoring is making sure the ship keeps to the passage plan that was prepared beforehand. The book calls it a primary function of the Officer of the Watch. The OOW may do it alone, with help from other crew, or as a back-up and information source for another officer who has the con.

Source: SWIFT, A. J.; BAILEY, T. J. Bridge Team Management: a practical guide. 2nd ed. London: The Nautical Institute, 2004. Chapter 5 — Monitoring the Ship's Progress (pp. 41-46).

Edital: Anexo 2-B, Área III, item 1 (Swift & Bailey) → Chapter 5 — Monitoring the Ship's Progress · Anexo 2-A, Área III, item 11 (Manobra de embarcações em águas restritas — "Monitoring the ship's progress"; rubrica literal do tópico).

Whatever the arrangement, monitoring always follows the same loop: carry out a set of functions, analyse the results, then act on that analysis. The chapter walks through the tools of that loop — fixing the position, checking it against an estimate, watching cross-track error and time, keeping a proper lookout, using natural aids such as transits and leading lines, and treating satellite navigation with the right caution.

2. Fixing method — establishing the position

The first requirement of monitoring is to establish the position of the ship. The methods range from very basic to highly technical — but the output is always the same. However the fix is obtained, the OOW ends up with no more than a position; what matters is how that information is used.

2.1 Fix frequency and regularity

Fix frequency is set at the planning stage, but it may need revising. The governing rule: the minimum frequency must be such that the ship cannot get into danger between fixes. Beyond being accurate and frequent enough, fixing also needs to be regular — evenly spaced, not just often. If the required interval falls below about three minutes, conventional fixing becomes too demanding and a continuous method such as parallel indexing should be used instead.

3. Estimated Position and soundings — the cross-checks

Regular fixing lets each fix be checked against an estimate. After every fix, it is good practice to estimate the position the ship will reach at the next fix. With regular intervals this is easy — pick off the distance between the present and previous fix and check it against the anticipated speed.

3.1 Soundings

It is also good practice to read the echo sounder at the moment of fixing and write that reading on the chart beside the fix. If the observed depth differs from what the chart predicts, the OOW knows immediately something is not right — the chart may be wrong, or the ship may be standing into danger.

4. Cross-track error and time management

Once the position is fixed, the OOW knows whether the ship is on the planned track and whether it will reach the next waypoint on time. If it is deviating, the navigator must judge whether the deviation will lead the ship into danger and what to do about it. Except when deviating to avoid an unplanned hazard such as an approaching ship, there is seldom justification not to correct the deviation and bring the ship back onto the planned track.

4.1 The Rule of the Road overrides the plan

No passage plan can override the Rule of the Road (the COLREGs). The Rules are clear and internationally understood:

RULE 16: "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."

RULE 8 makes clear that the give-way ship must keep clear — by altering course, or if that is impossible by reducing speed, or both together. Proper planning should ensure the ship is never in a position where such action cannot be taken. In heavy traffic near dangers, the person with the con holds a delicate balance between keeping track and avoiding other ships. The priority is to avoid collision — but not at the expense of grounding.

4.2 Non-navigational emergencies

The bridge team must never let the reaction to an emergency so dominate their response that the ship is put into a hazardous situation — for example, accidentally entering an area of high danger. Planning should allow for contingencies, but even the best plan cannot cover every situation. Situational awareness, careful assessment of changing circumstances, and the principles of bridge team management help stop a bad situation from getting worse.

4.3 Time management

If the ship is ahead of or behind the planned ETA at the next waypoint, the OOW judges whether to adjust speed. Sometimes the ETA is critical — for example when the ship must make a tide — and then the ETA must be adhered to. In either case, whether to advise the master is governed by night or standing orders, or left to the OOW's discretion.

5. Lookout — the full sense of the word

The OOW's situational awareness improves through structured team management and his own self-discipline in keeping a good professional watch — which includes confirming that a good lookout is kept. A good lookout means far more than the OOW personally watching the surroundings by eye.

RULE 5 (COLREGs 1972, ratified 1977): "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 the Rule addresses collision, it also applies to maintaining situational awareness. Lookout must be read in its fullest sense, covering all of the following:

Situational awareness is further enhanced when the OOW observes the environment by all available means, not limiting himself to the routine of fixing and correcting.

6. Monitoring aids — confirming track without a full fix

Beyond formal fixing, several features let the OOW confirm at a glance that all is well. None replaces a fix, but each adds confidence quickly.

6.1 Under-keel clearance and waypoints

Routine observation of the echo sounder must be one of the standing procedures of the watch (under-keel clearance). Waypoints are not only points on the chart where a change of status or event occurs — they are also good indicators of whether the ship is on time. If it is not, something has affected the passage and the OOW takes steps to correct it.

6.2 Transits (ranges) and leading lines

A transit (range) is an important navigational feature: it can cue a decision such as a wheel-over, or serve a more passive role — confirming the ship is on schedule or still on track, especially just after an alteration. Even a minor confirming transit reassures the observant OOW that all is as it should be.

Leading lines — the transit of two identifiable shore marks on the extension of the required ground track, usually charted — are used to make sure the ship is safely on the required track. The OOW may also pick up informal natural leading lines, e.g. a navmark in line with the end of land that confirms the vessel is on track.

6.3 Off-track distance from a head mark

Observing a head mark and doing a quick mental calculation gives the distance the ship has deviated from her track. The off-track distance in cables equals:

where "$\sim$" is the difference between the required and observed bearings. Alternatively, the off-track distance can be judged by looking down the required bearing and estimating the gap between the head mark and where the observed bearing meets the land — man-made features such as cars, buses and lamp posts help that estimate.

6.4 Clearing marks, rising/dipping distances and light sectors

7. Satellite navigation — power with caution

Navigational satellites let a ship fix its position at any time — one of the great achievements of modern technology. But, like all systems, incidents have happened when least expected. The book restates its guiding principles, which apply to satellite navigation too:

7.1 Two key factors to monitor

With satellite navigation, two things need watching. The first is equipment failure — in the satellite and in the onboard set. The second is the geographical reference of the satellite compared with the chart: in reality many charts show the land in the wrong position (hardly surprising, since the original surveyors had no satellites). So great care is needed when making a landfall, especially in less busy parts of the world, and when changing from one chart to another.

7.2 The OOW is an observer, not the builder of the fix

All of this depends on the OOW putting his own input into the system. The precise display of an integrated system can tempt the navigator to treat it as failsafe and not needing constant surveillance — which may well be wrong, because failed electronics may not be self-correcting nor give an obvious warning (the book cites the Royal Majesty, Bermuda to New York). GPS does not lessen the need for careful, diligent navigation. It must be emphasised: the navigator has had no part in constructing a GPS fix and is merely an observer. A GPS fix is no more than an easier way of getting a fix — and it is the way the fix is used that makes it contribute to safe navigation.

8. Monitoring the ship's progress in one view

Monitoring is the running check that turns a passage under way into a safe one — a loop of fix, analyse, act, supported by cross-checks, lookout, natural aids and disciplined use of electronics.