Passage Planning: Appraise, Plan, Execute, Monitor

Prerequisites

This lesson covers voyage and passage planning at the standard of an Officer of the Watch (Unlimited) under STCW Table A-II/1. On most ships the second officer is the navigating officer and prepares the passage plan for the master's approval, so expect to do this job soon after you qualify. Before starting you should:

Be confident with chartwork, tidal calculations (Admiralty Tide Tables NP201) and position fixing.
Have studied the radar and ARPA lesson (parallel indexing) and the ECDIS lesson (safety settings, route check, CATZOC).
Understand the steering and sailing rules, especially Rule 10 for traffic separation schemes.
Have basic knowledge of ship stability and draught, and of how a ship turns (turning circle, advance and transfer).

Learning Objectives

By the end of this lesson you will be able to:

State the legal requirement for passage planning (SOLAS V/34) and the four stages of IMO Resolution A.893(21).
List the publications and information used in the appraisal, and what each provides.
Mark no-go areas and margins of safety, and set a safe track berth to berth.
Calculate wheel-over positions from turn radius and course change, and mark them with independent references.
Set parallel index lines, clearing lines, abort points and contingency plans.
Calculate under-keel clearance including squat, and plan tidal windows.
Describe how the plan is executed and monitored, and when it must be changed.

Why Passage Planning Matters

Most groundings investigated by the MAIB involve a failure of passage planning or monitoring: a plan that ran over a shoal, a plan nobody checked, or a good plan that was not followed. A thorough plan does three things:

It lets the master and navigating officer think through the passage before the pressure of the moment, in daylight, with all the books open.
It gives every OOW a clear picture of what "safe" looks like at each point: the track, the limits, the dangers, when to call the master.
It gives the OOW early warning that something is wrong: an echo inside a PI line, a depth less than expected, an ETA slipping past a tidal window.

The legal basis

SOLAS Chapter V Regulation 34 requires that, prior to proceeding to sea, the master ensures the intended voyage has been planned using the appropriate nautical charts and publications, taking into account the guidelines and recommendations developed by IMO. The plan must identify a route that:

takes into account any relevant ships' routeing systems;
ensures sufficient sea room for the safe passage of the ship throughout the voyage;
anticipates all known navigational hazards and adverse weather conditions; and
takes into account the marine environmental protection measures that apply, and avoids as far as possible actions and activities which could cause damage to the environment.

Those guidelines are IMO Resolution A.893(21), Guidelines for Voyage Planning. In the UK, MGN 315 reinforces them for the OOW, and the ICS Bridge Procedures Guide gives detailed checklists. The plan covers the whole voyage berth to berth, including pilotage waters. The presence of a pilot does not remove the need for a plan.

The Four Stages

A.893 divides passage planning into four stages. They are not a one-off sequence: monitoring feeds back into planning whenever circumstances change.

Stage 1: Appraisal

Appraisal is gathering and weighing all the information relevant to the voyage, and deciding whether and how it can be made safely.

Information about the ship

Draught fore and aft at departure and expected at arrival, and how it will change with fuel and water consumed. Allow for trim, density of water (fresh water allowance) and heel.
Air draught for bridges, cables and gantries.
Manoeuvring characteristics: turning circles, stopping distances, squat tables (from the wheelhouse poster and manoeuvring booklet required by IMO).
Condition of machinery and equipment: any defects in steering, engine, radar, ECDIS, gyro.
Cargo: dangerous goods, deck cargo sensitive to rolling, stability limits.
Crew: watchkeeping arrangements, rest hours, experience, any need for extra lookouts or a second officer on the bridge in pilotage.

Publications and sources

Source	What it gives the planner
Admiralty charts or ENCs (best scale)	The primary navigational data; check corrections and edition
NP100 The Mariner's Handbook	Chart use and accuracy, IALA buoyage, ice, ocean currents and meteorology, practical guidance
Sailing Directions (Admiralty Pilots)	Coastal detail, dangers, port approaches, local regulations, anchorages, currents, weather, pilotage arrangements
NP136 Ocean Passages for the World	Recommended routes and distances for ocean passages, by season
Routeing charts (monthly, by ocean)	Prevailing winds, currents, ice limits, gale and tropical storm frequency, load line zones, recommended routes
Admiralty List of Lights and Fog Signals	Full light characteristics, heights, ranges, fog signals
Admiralty List of Radio Signals	Coast radio stations, VTS and reporting systems, port operations, weather and navigational warning broadcasts, GMDSS
Admiralty Tide Tables (NP201 to NP204) and tidal stream atlases	Heights and times of tide; tidal stream rates and directions
Notices to Mariners (weekly) and annual summary	Corrections, temporary and preliminary notices, annual notices (for example on piracy, submarines, distress)
Navigational warnings (NAVTEX, NAVAREA, coastal)	Current hazards: wrecks, unlit buoys, exercises, cable laying
IMO Ships' Routeing	TSSs, deep-water routes, areas to be avoided, mandatory ship reporting systems
Load Line Zones chart	Zone and seasonal area boundaries, to make sure the ship is never overloaded
Weather forecasts and routeing services	Expected conditions, tropical storms, ice
Company and charterer's instructions, port information, master's standing orders	Minimum UKC, passing distances, fixing intervals, reporting requirements

Also consider: marine environmental areas (MARPOL special areas, emission control areas where fuel changeover is needed, particularly sensitive sea areas), ballast water exchange areas, piracy high-risk areas and military exercise areas.

The appraisal decision

At the end of the appraisal, the master and navigating officer should be able to answer: Is this voyage possible with this ship, this draught, this crew and this season? What are the critical stages? Where is the margin for error smallest? Where would we go if things go wrong?

Stage 2: Planning

The plan is drawn on the charts or ECDIS, and summarised in a written passage plan (often a company form or the ECDIS route table). It covers the whole voyage, berth to berth.

No-go areas and margins of safety

Mark no-go areas: all water where the depth is less than the safety depth (draught + squat + UKC allowance), allowing for the height of tide you can rely on for that leg. On paper charts these are hatched; on ECDIS the safety contour and user-defined areas do the same.
Mark other areas to avoid: wrecks, restricted and prohibited areas, areas to be avoided in routeing schemes, firing ranges, offshore installations with safety zones (500 m), fish farms, wind farms.
Lay the track with a margin of safety: a minimum distance from any no-go area. Typical company figures might be 1 nm in coastal waters and more in open sea, adjusted for CATZOC, fixing accuracy, the ship's size and the weather.

The track

Courses and distances for each leg, as true courses, with the ECDIS XTD limit for each leg.
Routeing systems: use TSSs correctly (Rule 10): join or leave at the ends, or at as small an angle as practicable from the side; cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.
Speed and ETAs: planned speed for each leg, the ETAs at key points (pilot boarding, tidal gates, daylight requirements).
Chart changes: mark where to change chart or cell.
Reporting points: VTS, mandatory reporting systems, port control and pilot station calls.
Engine and steering changes: where to put the engine on standby, test the steering, change to hand steering, put extra lookouts on, call the master.

Wheel-over points

Large ships do not turn at the waypoint. They turn on an arc, which begins before the course alteration point. The point where the helm order is given is the wheel-over point (WOP).

For a turn of Δ degrees at a steady radius R, the arc starts R × tan(Δ/2) before the intersection of the two legs. Add a small allowance for the time between giving the order and the ship starting to turn.

Wheel-over geometry for a 60° alteration with a 0.5 nm turn radius, marked by a beam bearing of a tower

Worked example: Course alteration from 000° to 060° (Δ = 60°). From the manoeuvring data at 12 knots with 10° of rudder, the turn radius R = 0.5 nm.

R × tan(Δ/2) = 0.5 × tan 30° = 0.5 × 0.577 = 0.29 nm.
Allow 0.1 nm for rudder response at 12 knots (about 30 seconds).
Wheel-over point: 0.39 nm before the waypoint.

Rate of turn

Many ships turn using a constant rate of turn (ROT) instead of a fixed rudder angle. The radius and ROT are linked by speed:

ROT (degrees per minute) ≈ 0.955 × speed (knots) ÷ radius (nm)

At 12 knots with R = 0.5 nm, ROT ≈ 0.955 × 12 ÷ 0.5 ≈ 23° per minute. A 60° turn takes about 2.6 minutes. If you are slower, the same ROT gives a smaller radius, and you must move the wheel-over point.

Marking the wheel-over point

The WOP must be identifiable without relying on GNSS:

A beam bearing of a charted, conspicuous object (as in the diagram, "tower bearing 270°").
A transit of two charted objects.
A radar range on a radar-conspicuous object, often marked on the parallel index line.
In ECDIS, the WOP is shown on the route and a critical point alarm warns of the approach, but always back it up with an independent reference.

Parallel index lines and clearing lines

Parallel index (PI) lines: for each leg in coastal or pilotage waters, choose a radar-conspicuous object and note its cross index range. Record it in the plan so the OOW can set it up on the radar. Mark wheel-over points along it.
Clearing bearings: a bearing line on a charted object which, if the ship stays on the safe side (for example "Light not less than 045°"), keeps it clear of a danger. Mark them on the chart as NLT and NMT bearings.
Clearing ranges: a minimum radar range off a point.
Leading lines and transits: for narrow channels.

Under-keel clearance

UKC = charted depth + height of tide − (static draught + squat + other allowances)

The other allowances include:

Squat: the ship sinks and changes trim when moving in shallow water. A common estimate (Barrass) is: maximum squat ≈ Cb × V² ÷ 100 metres in open shallow water, roughly double that in a confined channel, where Cb is the block coefficient and V the speed through the water in knots. A tanker with Cb 0.82 at 10 knots: 0.82 × 100 ÷ 100 ≈ 0.8 m in open water, about 1.6 m in a channel. Halving the speed reduces squat to about a quarter.
Heel: a ship heeling increases draught at the bilge. For a box-shaped ship, increase ≈ (half the beam) × sin(heel angle). A 40 m beam ship heeling 5° adds about 20 × 0.087 = 1.7 m.
Wave response: pitching, rolling and heaving in swell.
Water density: lower density in fresh or brackish water increases draught (fresh water allowance).
Tide prediction error and surge: actual heights can differ from predictions, especially with strong winds or a high barometer (negative surge).
Survey quality: CATZOC uncertainty in depth.

Worked example: charted depth 12.0 m, predicted height of tide 2.4 m, static draught 11.5 m, squat 1.0 m. UKC = 12.0 + 2.4 − (11.5 + 1.0) = 1.9 m. If the company minimum is 10% of the static draught (1.15 m) the passage is acceptable, but only while the tide is at least 1.65 m above datum. That gives the tidal window: the times either side of high water when the tide height exceeds 1.65 m. Plan the ETA at the shoal within the window, with margin for delay. Check the actual company UKC policy; figures vary by area and company.

Abort points and contingencies

On the approach to a port, a narrow channel or a lock, there comes a point beyond which the ship cannot safely turn round or stop. Plan for it.

Abort point before the point of no return on the approach to a harbour, with a contingency anchorage

Point of no return: the position after which the ship is committed to the passage, because there is no room to turn, stop or anchor safely.
Abort point: a position, before the point of no return, at which the decision to continue or abort must be made. Mark it on the chart with an independent reference (a bearing or radar range).
Go criteria: list them in the plan. For example: pilot on board, tugs fast, visibility over 1 nm, berth confirmed clear, wind under 25 knots, engine and steering tested, UKC confirmed. If any criterion is not met at the abort point, abort.
Abort action: what to do. For example: turn to starboard into the deep water, or stop and hold position.
Contingency anchorages: safe places to anchor if the plan fails, with depth, holding ground, shelter and swinging room noted.
Contingency plans for engine or steering failure, loss of GNSS, fog, emergency anchoring, and for when the master or pilot is incapacitated.

Approval

The master approves the plan before departure. The plan is then briefed to all the officers. Any later change to the route must be treated as a new plan: checked, approved and briefed. The Muros grounding in 2016 followed a route revision on ECDIS that the master never saw.

Stage 3: Execution

Execution is carrying out the plan, with the tactics decided in the light of the conditions at the time.

Final decisions: confirm ETAs at critical points against tidal windows and daylight; adjust speed to arrive at the right time.
Weather: get updated forecasts and adjust the plan.
Traffic: expect concentrations at TSSs, port approaches and fishing grounds at known times.
Bridge team briefing: before departure and before each critical phase (landfall, TSS, pilotage), brief the bridge team on the plan, their roles, and the abort and contingency arrangements.
Equipment checks before arrival and departure: steering gear test, engine on standby, radars, ECDIS settings, communications, whistle, anchors cleared away and ready.
The pilot: exchange information (the master-pilot exchange). The pilot's plan must be compared with the ship's plan; differences must be discussed and resolved before entering confined waters, not during.

Stage 4: Monitoring

Monitoring means constantly checking that the ship is following the plan and that the plan is still safe.

Fix the position at the planned interval, using the planned primary method and cross-checking with another. Compare GNSS with radar and visual fixes; use PI lines continuously in pilotage waters.
Check cross-track error and correct promptly. Allow for set and leeway; note the course made good and adjust the course to steer.
Check depth: the echo sounder against the charted depth plus tide. A shallower reading than expected is an early warning of a position or tide error.
Check ETA against tidal windows and abort points.
Watch for changes: weather, visibility, traffic, equipment faults, a navigational warning received during the passage. Any of these may require the plan to be changed.
Record fixes, alterations and significant events in the deck log.

If the ship deviates from the plan, the OOW must act at once to return to safe water and inform the master. If the plan itself is no longer safe, call the master: changes to the plan need his approval.

Worked Example: Coastal Passage with a Tidal Gate

Situation: A 190 m bulk carrier, static draught 10.6 m, Cb 0.80, is to pass through a channel with a charted least depth of 11.0 m, between two banks. The master's standing orders require a minimum UKC of 1.0 m in this channel and a speed of 10 knots through it. The channel is 0.8 nm wide.

Step 1: squat. Confined channel at 10 knots: Cb × V² ÷ 50 = 0.80 × 100 ÷ 50 = 1.6 m. (Open water would be 0.8 m; use the confined figure here.)

Step 2: required height of tide. Required depth = draught + squat + UKC = 10.6 + 1.6 + 1.0 = 13.2 m. Height of tide needed = 13.2 − 11.0 = 2.2 m above chart datum.

Step 3: tidal window. From the tide tables, HW 1430 height 4.6 m, LW 0815 height 0.8 m and LW 2050 height 0.7 m. Using the tidal curve, the tide is above 2.2 m from about 1050 to 1805. Allowing a margin for prediction error and for the time to transit the channel (50 minutes), plan to enter after 1130 and to clear before 1730.

Step 4: ETA. The channel entrance is 76 nm from the morning position at 0400. At 13 knots, the ETA is 0951, too early. Plan to reduce to 11 knots, ETA about 1055, then 10 knots on the approach to arrive at 1130.

Step 5: abort point. Mark an abort point 2 nm before the entrance, with a radar range on a headland. Go criteria: tide above 2.2 m confirmed by the tide gauge report from VTS, visibility over 2 nm, no deep-draught traffic in the channel, steering and engine tested. If any is not met, abort by turning to starboard into the deep-water holding area, where a contingency anchorage is marked.

Step 6: monitoring. In the channel, use PI lines on both banks' radar-conspicuous beacons, fix every 3 minutes, monitor the echo sounder continuously, and keep the speed at 10 knots to limit squat. The master is on the bridge with an OOW and a helmsman.

Step 7: the delay. Suppose instead that a main engine fault delays the ship so that she cannot reach the entrance before 1720. With a 50-minute transit she would clear the channel at about 1810, after the window has closed. The plan must be changed: wait at the contingency anchorage for the next tide, rather than "hoping it will be all right".

Common Mistakes

Planning only pilot to pilot. The plan must cover berth to berth, including pilotage.
Not allowing for squat. It is the forgotten metre that turns a 1 m UKC into a grounding.
Turning at the waypoint. A large ship needs to start the turn well before; a late turn overshoots into danger.
Marking WOPs only on ECDIS. Mark them with an independent reference: beam bearing, transit or radar range.
No abort point. Without one, ships get committed into a channel with no pilot, no tug or no water.
Leaving no margin for the ETA. A tidal window planned to the minute will be missed. Build in time and plan for delay.
Copying last voyage's plan. Draught, season, notices and warnings change. Re-appraise every voyage.
Changing the route without approval. A revised route is a new plan: check it, get it approved, brief it.
Monitoring with a single source. GNSS on ECDIS is not monitoring on its own. Cross-check with radar, visual bearings and depth.
Ignoring CATZOC. Wide margins are needed in poorly surveyed areas.

Summary

SOLAS V/34 requires a voyage plan berth to berth; IMO A.893(21) sets out appraisal, planning, execution and monitoring.
Appraisal uses charts, NP100, Sailing Directions, Ocean Passages for the World, routeing charts, lights and radio signals lists, tide tables, notices, warnings, weather and ship's own data.
Plan no-go areas, margins of safety, courses, speeds, WOPs, PI and clearing lines, reporting points, abort points and contingencies.
WOP distance before the waypoint = R × tan(Δ/2) + reaction allowance. ROT ≈ 0.955 × speed ÷ radius.
UKC = charted depth + tide − (draught + squat + allowances). Squat ≈ Cb × V² ÷ 100 in open water, about double in a channel.
Decide go or abort at the abort point, before the point of no return.
The master approves the plan; any change is a new plan.
Monitor with more than one method, compare depths and ETAs, and change the plan when the situation changes.

Check Your Understanding

What does SOLAS V/34 require, and which IMO guidelines apply?

Answer: That before proceeding to sea the master ensures the intended voyage has been planned using appropriate charts and publications, identifying a route that takes account of routeing systems, gives sufficient sea room, anticipates all known navigational hazards and adverse weather, and takes account of marine environmental protection measures. The guidelines are IMO Resolution A.893(21), Guidelines for Voyage Planning.

Name four publications used in the appraisal and one thing each provides.

Answer: For example: Sailing Directions (local dangers, port approaches and regulations); NP136 Ocean Passages for the World (recommended ocean routes and distances by season); routeing charts (monthly winds, currents, ice and load line zones); Admiralty List of Radio Signals (VTS, reporting systems and broadcast times); Admiralty List of Lights (light characteristics); tide tables (heights and times); NP100 The Mariner's Handbook (chart use, buoyage, ice and meteorology).

A ship is to alter course by 90° with a turn radius of 0.6 nm. Allowing 0.1 nm for rudder response, how far before the waypoint is the wheel-over point?

Answer: R × tan(45°) = 0.6 × 1.0 = 0.6 nm, plus 0.1 nm allowance = 0.7 nm before the waypoint.

At 15 knots, what rate of turn gives a turn radius of 0.8 nm?

Answer: ROT ≈ 0.955 × 15 ÷ 0.8 ≈ 17.9°, about 18° per minute.

Calculate the UKC: charted depth 14.5 m, height of tide 1.8 m, static draught 13.2 m, squat 1.4 m.

Answer: UKC = 14.5 + 1.8 − (13.2 + 1.4) = 16.3 − 14.6 = 1.7 m.

Estimate the squat of a ship with Cb 0.75 at 12 knots in open shallow water and in a confined channel. What is the effect of reducing to 6 knots?

Answer: Open water: 0.75 × 144 ÷ 100 ≈ 1.1 m. Confined channel: about double, 2.2 m. Squat varies with speed squared, so halving the speed to 6 knots reduces it to about a quarter: about 0.3 m in open water and 0.5 m in a channel.

Explain the difference between an abort point and a point of no return.

Answer: The point of no return is the position after which the ship can no longer safely turn, stop or anchor and is committed to the passage. The abort point is a position before it at which the decision to continue or abort must be made, based on pre-set go criteria, leaving room to carry out the abort action safely.

Why should wheel-over points be marked with a beam bearing, transit or radar range as well as on ECDIS?

Answer: So that the moment to turn can be identified independently of GNSS and ECDIS, which may be wrong (sensor error, spoofing, wrong route). An independent reference also lets the OOW or pilot cross-check the ECDIS and keeps the turn accurate if the electronics fail.

Your ship is running 45 minutes late for a tidal window over a bar. What should the OOW do?

Answer: Recognise that the plan is no longer valid, recalculate the ETA against the window and the UKC, and call the master. The plan must be changed, for example by waiting at a contingency anchorage for the next tide, rather than pressing on. Record the decision.

List four things the plan should say about monitoring.

Answer: Any four of: the primary and secondary position fixing methods; the fixing interval for each stage; parallel index lines and clearing bearings or ranges to use; expected depths to compare with the echo sounder; XTD limits; points at which to call the master; reporting points; abort points and go criteria.