ICS Bridge Procedures Guide — Cap. 5: Operation and Maintenance of Bridge Equipment

1. Overview — Operating and Maintaining Bridge Equipment

Source: INTERNATIONAL CHAMBER OF SHIPPING. Bridge Procedures Guide. 6th ed. London: ICS, 2022. Chapter 5 — Operation and maintenance of bridge equipment.

Syllabus: Anexo 2-B, Área III (Navegação em Águas Restritas), item 3 — III.03 (ICS Bridge Procedures Guide), Cap. 5.

Masters and watchkeeping officers must be trained and competent in the ship's navigation and bridge equipment and familiar with how it works. Competence here means four concrete things: knowing the operating manuals well enough to configure safety-critical features, knowing how equipment and software updates are managed and how to verify they were applied, knowing the procedures for spotting and responding to equipment failures, and understanding the capabilities and limitations of every system on board. This Guide does not replace the makers' manuals — it works alongside them and alongside the user policies that belong in the SMS.

1.1 Carriage requirements and equipment performance

Masters and the officer in charge of the navigational watch should know the carriage requirements that apply to their particular ship. Keeping equipment fit for service is routine work: periodic checks are carried out, any defect is reported to the Master, recorded in the log book and, where relevant, flagged on the pilot card. Regular preventive maintenance follows the shipboard maintenance procedures and the manufacturers' instructions.

1.2 Software anomalies, ECDIS anomalies and cyber security

Navigation, communication and cargo systems all rely on software that must be suitable and stable. A defect in the design or operation of that software is a software anomaly, and it can compromise a system and put the ship at risk. The defences are: familiarisation so the crew know the equipment's normal operating condition; investigating any deviation from normal behaviour and applying the remedial measures in the guidance; and reporting new or unknown anomalies to the manufacturer.

ECDIS has its own history of operating anomalies, historically fixed through software updates. Standards have been modernised and anomalies now occur less often, but they can still happen — so the SMS must require data-presentation and performance checks after any software update or ECDIS upgrade, or whenever anyone has concerns about ECDIS performance. Many problems, though, are not anomalies at all: an OOW can misread information or set the system up incorrectly, which is why generic ECDIS training plus familiarisation with the specific ECDIS on board matters.

2. Steering Gear and Automatic Pilot

Steering control normally combines manual (hand) steering with an automatic pilot (autopilot) or other track-control system. Every steering position should have a gyro repeater and a rudder angle indicator; with an autopilot there is also a mode selector to switch between automatic and manual, and a manual override that gives immediate hand control. In an emergency, steering may fall back on alternative power supplies, the auxiliary steering gear, or direct control in the steering compartment.

2.1 Operation and testing

The OOW follows the SMS and the maker's requirements for operating and testing the steering gear. Three rules stand out for restricted-water work:

• In restricted waters or restricted visibility, a second steering-gear power unit is in operation so both units run simultaneously.
• The complete steering system is tested no more than 12 hours before departure.
• When approaching heavy traffic, restricted waters or restricted visibility, automatic steering is changed to hand steering in good time.

2.2 Heading control versus automatic track-keeping

The autopilot can work in two very different ways. In heading control it holds the ship's heading but cannot compensate for wind and tidal stream/current acting on the course over ground (COG) — the ship may keep its heading yet be pushed off track. When engaged this way, the OOW sets the yaw and rudder options to suit the sea state, which also saves fuel by smoothing out large rudder movements.

In automatic track-keeping the ship steers toward a waypoint or along a route while staying within a set cross-track distance (XTD), holding a COG that keeps it on track. How closely it follows the plan depends on the accuracy of the cross-track error (XTE) data the navigation system feeds the autopilot, and the OOW must monitor the alarm outputs and confirm the autopilot can alter course safely.

2.3 Off-course alarm

The steering-control system carries an off-course alarm that warns the OOW when the ship deviates from its heading. Suitable independent devices include a magnetic off-course alarm independent of other bridge equipment, or a second gyro/transmitting heading device with a heading-comparison unit. The alarm should always be in use whenever the autopilot is running and should be integrated with the BNWAS.

2.4 Berthing systems

Highly accurate berthing systems allow a precise approach to a berth. They are usually specific to a ship type or location and use laser, doppler or GNSS technology to measure the ship's movement relative to the berth or another vessel. The team should know which system is fitted and its capabilities and limitations.

3. Compass Systems

3.1 Magnetic compass

The magnetic compass sits above the navigating bridge on the centreline, read through a periscope from the helm. Where it must supply heading to other systems, a transmitting magnetic compass (TMC) is fitted; its outputs are corrected for compass error and it is tested once a week. A deviation card is kept visible on the bridge showing the magnet positions, and deviation is re-determined and the compass adjusted at intervals — especially after major steel work or when carrying magnetic cargoes such as iron ore and steel.

Every piece of electrical bridge equipment carries a compass safe distance, the minimum distance it may be installed from the magnetic compass. A TMC may apply variation automatically, but that does not include deviation — both variation and deviation must be applied correctly. Performance also degrades near the magnetic poles.

3.2 Gyro compass and GNSS compass

The gyro compass should run continuously. If it stops, it is restarted and checked regularly, and can be relied on again only once it has 'settled' and its error is known. Bridge gyro repeaters are checked against the master gyro at least once per watch and after significant manoeuvring; other repeaters, frequently. Gyro accuracy is reduced by low horizontal force in polar latitudes (around ±70° N or S).

A GNSS compass is a non-magnetic transmitting heading device — an alternative to the gyro that feeds heading to AIS, radar and plotting aids. A GNSS compass (or equivalent) is required in polar waters above 80° latitude.

3.3 Compass errors and rate of turn

Gyro and repeater headings are checked frequently so that any wandering is caught. Magnetic and gyro compass errors are checked and recorded each watch where possible, using azimuth or transit bearings. Separately, rate of turn (ROT) indication shows how quickly the ship is turning — valuable on large ships, where the bow is far from the pivot point, and used by automatic track-keeping to perform controlled turns.

4. Speed and Distance Log

Depending on type, the log measures speed and distance through the water or over the ground — a distinction that matters for collision avoidance.

Speed made good (SMG) can be found from two fixed chart points and is also computed by electronic position-fixing systems. As for the equipment itself, electromagnetic and doppler logs are either single-axis (fore-and-aft only) or dual-axis (fore-and-aft plus athwartships); combined with ROT data, a dual-axis log can give the speed and direction of movement of the bow and stern. Log distances are recorded in the log book at the end of each watch, the equipment is calibrated per the maker's instructions, and its distance can be cross-checked against GNSS for anomalies.

5. Echo Sounders

The echo sounder is always used when making a landfall and kept switched on in coastal and pilotage waters. If it has a shallow-water alarm, the alarm is set to a safe depth. The units of soundings must match those on the chart in use, and any comparison of echo and chart soundings allows for draught, any depth-reading offset and the height of tide. One firm limit: the depth alarm must never be set lower than the ship's sailing draught.

6. Bridge Navigational Watch Alarm System (BNWAS)

The BNWAS monitors bridge activity and OOW awareness and can detect operator disability before it causes an accident. It uses staged visual and audible alarms; if the OOW does not or cannot respond, the Master and other personnel are alerted automatically. The alert period is set long enough that alarms do not distract the OOW from watchkeeping, and the system also lets the OOW call immediate assistance to the bridge.

7. Navigation Lights and Signalling Equipment

The OOW makes sure the navigation lights, emergency navigation lights and signalling equipment are in working order and ready for immediate use. Lights, flags and shapes are checked at regular intervals, and sound signalling equipment is checked daily and kept operational.

8. Voyage Data Recorder (VDR)

A VDR records and securely stores information on a ship's position, movement, physical status and command and control. It lets accident investigators reconstruct the events leading to an incident and gives the company a comprehensive record for improving operations. A simplified VDR (S-VDR) stores a smaller range of data but still covers position, movement, status and command and control; any item that is mandatory for a VDR should also be recorded by an S-VDR when the interfaces exist.

8.1 What a VDR records

A VDR keeps a sequential record covering at least 48 hours, whose minimum contents are the data items summarised above.

8.2 Preserving records and testing

Retention differs by recording element, and knowing the figures is what lets a watchkeeper preserve the right data in time.

After those periods older records may be overwritten and lost, so all watchkeeping officers must know the SMS procedures for preserving records and avoiding overwrites. Testing is required annually and always after repair or maintenance to the VDR or to any source feeding it; the OOW confirms every required data item recorded correctly. The VDR is also checked before departure for correct functioning and absence of alarms, and company policy for playback — a tool for analysing bridge-team performance — is set out in the SMS.

9. Electronic Position Fixing — GNSS / GPS

Electronic position-fixing systems give an automatic, continuous position update to a suitable receiver. A GNSS is a satellite-based system providing continuous worldwide position, time and speed over ground. Two systems give near-global coverage — GPS (United States) and GLONASS (Russian Federation) — while BeiDou (China) and Galileo (EU) are also recognised components of the World-Wide Radio Navigation System (WWRNS).

Base GNSS accuracy is around 15–25 metres. A differential GNSS receiver improves that by applying corrections from ground-based reference stations.

9.1 Associated errors and alarms

The OOW must know the system fitted on board and watch its status display, because several distinct errors each demand a different response.

9.2 Receivers, geodetic datum and chart accuracy

As stand-alone or integrated equipment, GNSS receivers provide position (with service-quality and datum information), course and speed over ground, and route storage with XTD monitoring — entering the passage plan gives the OOW an independent way to monitor the passage. A caution attaches to the reference frame: a GNSS fixes position on a particular geodetic datum that may differ from the chart's datum, so a position could be plotted in the wrong place. Where the datum shift is known, a 'satellite-derived positions' note on the chart gives the offset to apply; many receivers transform between datums internally.

10. Automatic Identification System (AIS)

AIS is a maritime mobile system that broadcasts on VHF and automatically exchanges data ship-to-ship and ship-to-shore. Its information falls into three classes:

10.1 AIS aids to navigation, satellite AIS and SAR

AIS increasingly carries Aids to Navigation (AtoN) information — the type, name, position and status of an aid (for example a buoy light failure or a buoy out of position) plus safety data such as tide or wind. Physical AtoN are real aids fitted with AIS transponders (buoys, lighthouses); virtual AtoN do not physically exist but are transmitted by a coastal authority for temporary needs — marking a wreck, a hazard or an area — and are not charted unless a temporary Notice to Mariners is issued. Satellite AIS (SAT-AIS) extends detection beyond coastal areas. Finally, some SAR devices — AIS-EPIRB, AIS-MOB and AIS-SART — use AIS to send distress alerts, and the OOW should know how they appear on AIS or on an AIS-integrated ECDIS.

11. Radar and Radar Plotting Aids

Watchkeepers should understand the difference between X-Band (3 cm) and S-Band (10 cm) radars — their characteristics and how weather affects each — and be familiar with the plotting aid integrated with the radar and the inter-switching between the two transceivers.

11.1 Characteristics and safe use

The OOW should know the radar fitted and its limits, and use its controls correctly: gain, rain and sea clutter; orientation (north-up, head-up, course-up); range scales; variable range markers (VRMs); electronic bearing lines (EBLs); range rings; pulse length; display offset; and performance monitoring. Radar is the main electronic collision-avoidance tool and supports passage monitoring, and unless switched off for safety it is kept running at sea and at anchor.

Range choice depends on visibility, traffic density, proximity of hazards and own speed. Beyond the working range, regular checks at shorter and longer ranges build situational awareness — short ranges reveal small targets, long ranges give early warning of land and high-speed craft, a key factor in safe speed. Parallel indexing should be practised regularly in coastal navigation.

11.2 Radar image overlay and collision avoidance

When a radar image overlay (RIO) is applied to an ECDIS chart, correct orientation, heading alignment and scale are crucial; the OOW confirms the radar image correlates with charted features and adjusts colour and transparency so contacts show clearly. RIO is not a substitute for an anti-collision plot on a separate radar/ARPA display.

To find a target's closest point of approach (CPA) and any risk of collision, radar needs accurate own-ship heading and STW. Yawing or input errors reduce vector accuracy — in head-on situations with strong currents, vectors may show a target passing clear when a collision risk exists. Multiple observations are needed to establish a target's course, speed and CPA; a single one is not enough, and the estimate is valid only up to the last observation. It must not be assumed that a changing relative bearing means no risk of collision.

11.3 Plotting aids and ARPA

ARPA offers automated collision-avoidance features, including a trial manoeuvre before acting. But the OOW must understand its possible errors and warnings, understand its limitations, treat the apparent precision of a digital display with caution as CPA nears the safe minimum, and regularly test the ARPA using its built-in self-test.

11.4 Automatic target acquisition and AIS targets

Guard zones can be set on ARPA so that targets entering them are automatically acquired; the OOW sizes and positions the zones to manage how many targets are taken. Automatic acquisition must be used with caution — hidden targets may not be detected, and it is not a substitute for a proper look-out, regular inspection of the image, or early manual acquisition of targets of concern.

Where the radar/ARPA is connected to the AIS transponder it can show AIS targets beside or merged with ARPA data, and the display must clearly indicate which is which. AIS data — especially CPA and time to closest approach (TCPA) — should not be relied on for collision avoidance.

11.5 Radar and navigation — parallel indexing

Near restricted visibility, radar is a valuable tool to fix the ship's position and cross-reference GNSS. The OOW checks overall performance, heading-line alignment, the accuracy of VRMs, EBLs and fixed range rings, and that any parallel index lines are correctly set.

Parallel indexing is a technique for assessing the distance at which the ship will pass a fixed object such as a headland. An index line is drawn parallel to the planned ground track, touching the edge of the object's radar echo at a range equal to the desired passing distance. It works in both relative motion — where the static object runs along the index line, reciprocal to the ground track — and in sea-stabilised true motion, where the VRM moves along the index as the ship closes the object. Radars may also display ENCs and electronic maps of buoys, channel limits and zones, but such maps must be used with caution and be correctly geo-referenced, as position or stabilisation errors cause misinterpretation.

11.6 Search and rescue transponder (SART)

A SART is a self-contained emergency device using radar or AIS technology. A radar-SART marks distress as a series of 12 dots on an X-band display — for stable reception, interference rejection is switched off. An AIS-SART is detected by AIS but does not appear on radar.

12. Charts, Publications and ECDIS

All ships must carry adequate and up-to-date official nautical charts, sailing directions, lists of lights and radio signals, Notices to Mariners, tide tables and every other publication needed to appraise, plan, execute and monitor a passage. A chart and publication management system records what is carried, the licences held, and when each item was last corrected. To be official, a chart or publication must be produced or approved by an authorised hydrographic office in line with IHO resolutions.

12.1 Electronic charts — ENC and RNC

ENCs are official vector charts storing hydrographic data in a database rather than a picture; ECDIS builds a system chart (SENC) from it and lets the OOW choose which features are shown and add information manually. RNCs are official raster charts — exact scanned copies of paper charts — whose display cannot be changed, so nothing can be hidden. Their strengths and weaknesses differ markedly.

13. Integrated Bridge and Navigation Systems (IBS / INS)

An integrated bridge system (IBS) and integrated navigation system (INS) use multi-function workstations that bring together some or all of the equipment covered in this chapter. The two integrate different families of function.

14. GMDSS Communications

A ship equipped with the GMDSS must be able to transmit ship-to-shore distress alerts by two independent means and receive shore-to-ship alerts (usually relayed by a Rescue Co-ordination Centre). It must also handle ship-to-ship alerts, SAR co-ordinating and on-scene communications, locating signals, Maritime Safety Information (MSI), routine shore traffic and bridge-to-bridge communications.

14.1 Equipment and sea areas

The mandatory equipment on SOLAS ships is:

Across the system, Digital Selective Calling (DSC) is used for calling and replying and for transmitting, acknowledging and relaying distress alerts. It lets a specific station be contacted by its maritime mobile service identity (MMSI), or a call be addressed to ALL SHIPS or ALL STATIONS.