When every screen agrees and every screen is wrong

Most bridge teams have a plan for losing GPS. The alarm sounds, the position goes to dead reckoning, and everyone knows something is wrong. The harder case is the one where nothing alarms at all: the position is wrong, but it looks right, and every display on the bridge agrees with it.

That is what happened on board the bulk carrier Rosco Poplar in Hydrographers Passage on 4 May 2022. The Australian Transport Safety Bureau (ATSB) published its findings in July 2024. The summary below is drawn from that report.

What happened

The 225 m ship was in ballast, at night, with a coastal pilot on board for the transit of Hydrographers Passage, a long and narrow route through the outer reef with strong tidal streams.

• 0145 The pilot boarded by helicopter, ordered full speed and set up the portable pilot unit (PPU).
• 0149 The passage waypoints were found to be loaded in the ECDIS only. The second mate spent much of the next stage entering them into the radars.
• 0239 The master and second mate noticed a heading discrepancy between radar and ECDIS. They discussed it between themselves but did not raise it with the pilot.
• 0301 A position cross-check was made using the ECDIS itself, which confirmed the false position.
• 0311 The pilot saw a sector light showing red and altered course immediately.
• 0313 GPS alarms sounded and the displayed position jumped about 0.92 nm east. The ship passed less than 200 m from Bond Reef, against a normal clearance of about 1,500 m.

Why no one saw it

The ship had three GPS units, but they fed a 3-way selector switch, and the output of the selected unit was split to supply the bridge equipment. The ATSB noted this "may have satisfied the IMO performance standards", yet it meant every navigation system took its position from one source at a time.

The selected unit, likely through an internal antenna fault, kept sending an invalid position without updating its accuracy information, so it raised no alarm. The ECDIS units and radars all showed the same wrong position. The GPS units were obsolete models, out of production since 2012, and were replaced after the incident with the bridge reconfigured to take multiple GPS inputs.

The pilot's PPU was plugged into the ship's AIS pilot plug and was not set to use its own position sensor. It showed the same error. The ATSB found the pilot incorrectly believed it was independent, and was unaware the settings could be changed.

The procedures were already written. The ship's own system called for position fixes by radar and visual observation at least every 30 minutes, and more often if GPS accuracy was in doubt. The pilotage provider required the PPU to use its own independent sensor and to be checked against leading and sector lights. On the night, neither happened.

The ATSB also found that no visual bearings or radar position checks were used during the transit, the master-pilot exchange did not set out roles and monitoring, and the bridge team did not share concerns with the pilot. When the reef VTS system raised a grounding alert, the operator judged it to be a system error and contact with the ship was delayed.

The report went further than the bridge. It found the check pilot system used to assure coastal pilot competency was not giving reliable results, and it made a safety recommendation to AMSA.

What saved the ship

A sector light. The oldest and simplest aid on the route, which needs no satellites and cannot be corrupted by a faulty antenna, told the pilot what every screen was hiding.

Navigate by more than one means, all the time

GNSS is a superb aid, but it is one aid. Good practice is to run at least one fully independent method alongside it for the whole passage, not only when something looks wrong.

Simulator exercises with GNSS degraded or switched off are a safe way to keep these skills current across the whole bridge team.

A growing threat: jamming and spoofing

Rosco Poplar's error came from a failing antenna. The same symptoms, a wrong position that looks right, can be produced on purpose. GNSS jamming and spoofing are now widely reported at sea, and in March 2025 the IMO, ICAO and ITU issued a joint call for states to protect satellite navigation, with the IMO Secretary-General warning that interference poses a serious risk to shipping, including collisions and groundings.

As the world becomes less stable, bridge teams should plan for GNSS being degraded, falsified or switched off, not just failing. Warning signs include sudden position jumps, a radar overlay that no longer sits on the chart, AIS targets shown over land, time or date errors, and several ships nearby reporting the same odd position. The defence is the same as above: independent sources, cross-checked as routine.

What has changed: MO 54 (Coastal pilotage) 2026

When the ATSB reported, AMSA advised that a review of coastal pilotage was underway. The new Marine Order 54 (Coastal pilotage) 2026, in force from 1 September 2026, now writes several of these lessons into law. Under Schedule 1, a pilotage provider's safety management system must include:

• a policy and procedure for PPUs covering use of the PPU with independent GNSS input, training in how to update software, interpret data and troubleshoot, refresher training at least annually, and maintenance and record keeping;
• a policy for information exchange between the master and the pilot;
• regular review of competency assessments, and sharing lessons from local, national and international pilotage incidents with every pilot;
• a policy and procedure for managing cybersecurity threats.

The Order also requires providers to give pilots AMSA's latest pilotage advisory notes. Pilotage Advisory Note 02/2024 on portable pilot units sets out the detail. In summary:

• the PPU should always use a position source independent of the ship's systems. If for any reason it does not, the provider's designated person and REEFVTS should be told as soon as practicable, and a documented risk assessment done before the pilotage starts or continues;
• a PPU that takes the ship's AIS feed should also have an independent SBAS or GNSS input, and AIS should not be relied on for position;
• the unit should be able to use SBAS such as SouthPAN, and give clear visual and audio warnings when accuracy drops or it falls back to dead reckoning;
• the agreed passage plan should be preloaded and discussed with the bridge team throughout, including any differences between the PPU and the ship's equipment;
• a PPU should never be the sole means of fixing position.

Lessons for pilots, masters and operators

1. Make the PPU genuinely independent. Run it on its own GNSS antenna, confirm the source on the screen at boarding, and compare it with the ship's position before you start. A PPU fed only from the ship's plug is a repeater, not a check, and under PAN 02/2024 it is an exception to be reported and risk assessed.
2. Know where each display gets its position. Ask during the master-pilot exchange how the GPS units feed the ECDIS, radars and AIS, and whether one fault can reach them all.
3. Check position by means that do not use GNSS. Visual bearings, radar ranges and parallel indexing on fixed marks, sector lights and depth, and celestial fixes on ocean passages. Plan where each check will be made, and make them at night as much as by day.
4. Treat a small discrepancy as a warning. A heading or position that does not quite agree is often the first sign. Anyone on the bridge who sees it should tell the pilot straight away.
5. Use the master-pilot exchange properly. Agree who monitors what, how position will be checked and what will be reported. Keep the officer of the watch on monitoring, not on tasks that could have been done before the pilot boarded.
6. Prepare the passage before the pilot boards. Waypoints in every system, equipment checked and the bridge team briefed.
7. Do not rely on VTS to catch it. VTS is another layer of safety. It does not replace the pilot and bridge team keeping their own position.
8. Operators: look at the design, not just the people. A single GPS feeding every bridge system is a single point of failure. Review sensor configuration, ageing equipment, cyber protection and how the crew are trained to spot a plausible but wrong position.
9. Plan for interference. Brief the bridge team on the signs of jamming and spoofing, and agree in the passage plan what you will do if GNSS cannot be trusted.

Why this matters now

Bridges are more integrated than ever, and the satellite signals they rely on are weaker and easier to disrupt than most people realise. The skills that saved Rosco Poplar are not new. They are the basic habits of position fixing and bridge teamwork, and they need to be practised and checked, not assumed.

Source: ATSB Marine Safety Investigation MO-2022-005, Near grounding of Rosco Poplar, off Bond Reef, Hydrographers Passage, Queensland, on 4 May 2022, published 26 July 2024 (atsb.gov.au). Marine Order 54 (Coastal pilotage) 2026, Compilation No. 1 (F2026C00930). AMSA Pilotage Advisory Note 02/2024, Portable pilot units (amsa.gov.au). Joint statement by ITU, ICAO and IMO on GNSS interference, March 2025. This article is a general summary for safety learning and does not replace the report.