A passage plan is judged less on whether the four stages are named correctly than on whether the numbers behind them — under-keel clearance, wheel-over geometry, fix intervals — actually hold up when checked. This chapter works through the mechanism behind each one, not just the rule.
Appraisal, planning, execution and monitoring are not four separate jobs on four separate days — they are one continuous loop, and the examiner is testing whether you can keep it turning rather than whether you can recite the names in order. Appraisal gathers the raw material: charts, publications, weather and the ship's own particulars. Planning turns that material into a track with decisions built into it — where the ship must not go, where she turns, where she could abort. Execution is planning meeting reality: pilotage, traffic, a squall that wasn't in the forecast. Monitoring is the constant check that reality still matches the plan, and it feeds straight back into the next appraisal, because every voyage teaches something the next one should use.
Where candidates lose marks is treating the four stages as paperwork completed once, at the start, and then abandoned. A plan appraised on Monday for a Thursday departure needs its weather and tidal data refreshed before sailing, not just filed. A plan that stops being monitored the moment pilotage is handed over stops being a plan at all — it becomes a hope.
The four stages describe a cycle that runs for the whole voyage, not a checklist ticked off before the anchor is weighed. Monitoring one voyage is appraisal for the next.
Appraisal is where a plan either gets built on solid ground or doesn't. It starts with charts and publications corrected to the latest Notices to Mariners — not "reasonably up to date", but corrected, with the correction log to prove it if asked. Routeing guides and pilot books carry the local knowledge that a chart alone can't: recommended tracks, traffic separation conventions, areas to avoid, local hazards that don't always show as a symbol. Weather and climatology matter beyond tomorrow's forecast — ocean routeing charts and pilot charts describe what a given sea area typically does in a given month, which is what lets a passage plan build in a sensible margin rather than a guess.
The ship herself is part of the appraisal, and it's the part most often skimped. Draught, air draught, trim, the turning circle and stopping distance at the speeds actually planned, and how she handles in shallow or confined water — all of it has to be on hand before a track is drawn, not looked up afterwards when a tight corner turns out to be tighter than the ship can manage. Port and pilotage requirements close the loop: berth restrictions, tug and mooring arrangements, reporting points, and any local rules that will shape the final approach.
Planning takes everything appraisal gathered and turns it into a track — and the track has to run berth to berth, including the pilotage waters at both ends. A plan that starts at the pilot station and stops at the next one has skipped the parts of the voyage where the ship is slowest, most confined and least forgiving of a mistake; examiners ask about this specifically because it's where real plans go wrong.
Four features carry most of the planning marks. A no-go area is water the ship cannot enter at any state of the tide — not "shallow", not "to be avoided if possible", but excluded outright once draught, squat and the UKC policy are applied to the charted depth. A wheel-over point is where the helm actually goes over so the ship rolls out on the new course rather than overshooting or cutting the corner; it has to allow for the ship's advance and transfer at the planned rate of turn, which is a function of speed and rudder angle, not a fixed distance before the corner. An abort point is the last position from which the whole manoeuvre — an approach, a pilotage, a berthing — can still be safely abandoned in favour of a known alternative; it has to be decided before it is needed, because working it out in the moment is a different exercise under a different kind of pressure. A contingency anchorage is that known alternative: somewhere the ship can actually bring up if the plan can't continue, chosen and checked in advance rather than picked off the chart in a hurry.
Under-keel clearance is a policy applied at a place and a moment, not a single number written once at the top of the plan. The relationship is straightforward to state and easy to get wrong in practice:
Charted depth comes off the chart at chart datum, and height of tide adds back whatever the tide actually gives at the moment the ship is there — which means the UKC at a given shoal is different at every state of tide, not fixed. Draught should be the actual draught for that leg of the voyage, corrected for trim and, where the passage crosses from salt to fresh water, for the change in density. Squat is the part most often left out of a quick mental check: it grows with the ship's block coefficient and, in the shallow-water approximation, with the square of her speed, so a small increase in speed through a confined reach can cost disproportionately more UKC than the speed increase suggests.
The "required margin and survey allowance" in the formula is what turns a raw depth calculation into a policy figure: an allowance for the accuracy and age of the survey the chart is based on, plus whatever the company adds for sea state, squat variability and simple error. None of that is constant either — a chart surveyed to modern standards earns a smaller allowance than one surveyed a century ago and never resurveyed since.
UKC is recalculated at every critical point on the track, at the state of tide and speed actually planned there — never quoted as one figure for the whole passage.
ECDIS route checking is part of planning, and it earns that place because it catches what a visual scan of the chart can miss — a single sounding inside an otherwise clear channel, an isolated danger just off the planned track, a stretch where the margin looks fine at a glance but isn't once measured properly. Two settings decide what the check actually finds. The safety contour is the depth contour the navigator selects to separate water the ship can safely use from water she can't — set from the ship's draught, the squat expected on that leg and the UKC policy, not left at a system default. The safety depth controls how soundings shallower than that contour are emphasised on the display; it affects what stands out to the eye, not what the automated check treats as a danger.
Route checking against the correct safety contour is what turns the exercise from a formality into a real check: run it with the contour set incorrectly and the system will either miss genuine dangers or bury the watchkeeper in false ones, and either failure defeats the point of running it at all. Every alarm the check raises has to be examined and resolved — accepted as a real hazard the plan must route around, or dismissed with a documented reason if it genuinely isn't one. Silencing an alarm without resolving it removes the evidence that the danger was ever considered, and it is one of the most consistently penalised mistakes in this part of the syllabus.
Execution is the plan meeting the conditions of the day, and monitoring is the discipline that keeps the two connected once pilotage, traffic or weather start pulling the ship away from the plotted track. The practical tools are simple and deliberately so: parallel indexing gives a continuous, visual check of cross-track distance on radar without waiting for the next fix; position fixing at the interval stated in the plan — shorter in confined water, where the tolerance for error is smaller — confirms where the ship actually is; and cross-checking independent position sources against each other catches a single failed or degraded source before it can put the ship somewhere the plan didn't intend.
None of this replaces judgement. The plan is the master's plan, even though the mate usually writes it, and executing it well means recognising early when conditions have moved outside what the plan assumed — a set stronger than allowed for, visibility closing in before a critical turn — and using the abort points and contingency anchorages already built in, rather than improvising a solution under pressure. Monitoring one passage is also the start of appraising the next: deviations, near misses and anything that didn't go to plan belong in the record, because that record is exactly the local knowledge the next appraisal needs.
The three problems below chain the ideas above together — under-keel clearance under way, turn geometry weighed against a crew-readiness margin, and channel tolerance set against a monitoring interval — each worked the way an oral examiner expects it stepped through.
A bulk carrier of block coefficient C_B = 0.78 must cross a shoal reach with a charted depth of 14.20 m (chart datum). The tide at the planned transit time gives a height of tide of 1.80 m. The ship's draught is 12.40 m and she will run the reach at 10 knots. Company policy sets a minimum net under-keel clearance of 1.30 m at any point on the track. Is the transit safe at this speed and time, and what margin does it leave?
Charted depth (chart datum) = 14.20 m Height of tide = 1.80 m Draught = 12.40 m Speed through the shoal reach = 10 kn Block coefficient C_B = 0.78 Required minimum net UKC (company policy) = 1.30 m
Find the squat at the planned speed using the shallow-water approximation from the reference sheet.
Add the tide to the charted depth to get the water actually available over the shoal at the transit time.
The ship does not occupy just her draught.
Add the squat, since that is how much deeper she sits once moving.
Under-keel clearance is what is left once the ship's occupied depth is taken from the water available.
Compare against the policy minimum.
The plan is only safe if the working UKC clears it with margin to spare.
AnswerUKC at the shoal = 2.82 m, which is 1.52 m clear of the 1.30 m policy minimum — the transit is safe at 10 kn at this state of tide.
The trap: comparing draught alone against the charted depth and ignoring squat — at 10 kn the squat here consumes more than a quarter of the whole under-keel margin, and it grows with the square of the speed, not in proportion to it.
The passage plan calls for a course alteration at a charted turn point from 000°(T) to 090°(T) — a 90° change of heading. The ship's pilot card gives a turning radius of 0.6 nm at the planned manoeuvring speed of 12 knots, and the bridge procedure requires the OOW to be alerted at least 3 minutes before wheel-over so the helm and lookout can be readied. Where should the wheel-over point be marked, and where should the alert be triggered?
Course change at the turn point = 000°(T) to 090°(T), θ = 90° Turning radius at planned speed, R = 0.6 nm Speed through the turn = 12 kn Required crew-alert lead time before wheel-over = 3 minutes
Model the turn as a constant-radius arc.
The wheel-over point sits back from the plotted corner by the tangent length of that arc, R·tan(θ/2).
Convert that distance into time at the planned speed.
Since the alert has to be timed, not just plotted.
Check that against the bridge procedure.
The 3.0 minutes available exactly equals the required alert lead time — there is no spare margin if the ship is running even slightly ahead of plan.
Build in a margin by moving the alert 1 minute earlier than the bare geometric minimum, then convert that back to a distance before the turn point.
AnswerWheel-over point = 0.6 nm before the turn point on the 000° leg; the crew alert should be triggered 0.8 nm before the turn point (0.2 nm before the wheel-over point itself) to preserve the 3-minute lead time with a working margin.
The trap: marking only the wheel-over point and using it as the alert trigger too — at speed, the geometric margin and the crew-readiness margin are not the same distance, and treating them as one can leave no time to react if the ship arrives at the turn early.
A dredged channel has a usable width of 500 m and the ship's beam is 20 m. The passage plan holds a planning margin of 40 m clear of each bank edge to allow for squat, wind and current effects. Previous fixes show the current is setting the ship off track at about 25 m per minute. The plan uses parallel indexing off a charted point to monitor position. How much cross-track tolerance does the plan actually have, and how often must the ship be fixed to keep a working margin for correction?
Usable channel width = 500 m Ship's beam = 20 m Planning margin required clear of each bank = 40 m Estimated cross-track set = 25 m per minute Monitoring method = parallel index off a charted point
How much cross-track tolerance does the plan actually have, and how often must the ship be fixed to keep a working margin for correction?
Find how much room the ship's centreline has to wander on each side before the hull itself reaches the planning margin.
Subtract the planning margin.
Since that space is reserved for squat, wind and current and is not available as track tolerance.
Turn the tolerance into time using the estimated set.
To find how long the ship has before the limit is reached if nothing is corrected.
The fix interval has to leave room to notice the drift and correct it.
Not just detect the limit as it is reached — so it must be a fraction of the time-to-limit, not the whole of it.
AnswerAllowable cross-track tolerance = 200 m; at the estimated set that is reached in 8 minutes, so fixes (and parallel index checks) through this stretch must be taken at intervals of no more than about 4 minutes to leave a working margin to correct.
The trap: carrying an open-water fix interval into a confined channel because the ship's speed hasn't changed — the interval has to shrink because the tolerance for error has shrunk, not because the ship is moving any faster.
Four stagesAppraisal → planning → execution → monitoring, run as a continuous loopUKC = charted depth + HoT − draught − squatLess the required margin and survey allowanceSquat ≈ C_B·V²/100 (shallow water, approx.)Grows with the square of speed — a small speed rise costs a large squat riseNo-go areaWater excluded at any state of tide, not just at low waterWheel-over point ≈ R·tan(θ/2) back from the turnR = turning radius, θ = change of courseAbort pointLast position the plan can still be safely abandoned — decided in advanceContingency anchorageA checked, known alternative if the plan cannot continueParallel indexContinuous cross-track check on radar, independent of the fix intervalFix intervalStated in the plan; shortens in confined or high-risk waterECDIS safety contourSet from draught + squat + UKC policy — never left at default