GNSS receivers and position integrity
What is being checked
The inspector is checking whether GNSS receivers provide correctly configured position, datum, integrity and timing information that is continuously checked against independent sources, with officers able to configure, cross-check, test and respond to failure of the actual equipment fitted.
Ready onboard
0/6 completePractice questions
Answer aloud, then open the preparation point.
1What safety function does gnss receivers and position integrity provide?
Gnss receivers provide correctly configured position, datum, integrity and timing information that is continuously checked against independent sources.
2How is the complete function tested?
Run the approved receiver test, compare independent receivers and terrestrial, radar, visual or inertial information, and verify downstream ECDIS, AIS, VDR and GMDSS inputs.
3What is its principal limitation?
GNSS can suffer jamming, spoofing, constellation error, antenna or cable failure and common-mode failure across several displays.
4What is your response if it fails?
Reject suspect data, select an independent source, increase fixing by terrestrial and radar methods, assess downstream systems, call the Master and report interference where required.
5Show the latest test and operational evidence.
Link the dated record to the actual unit, test method, result, defect response and restoration; a panel lamp test alone is not sufficient where the full signal path can be tested.
Where an observation may arise
The responsible officer cannot explain safe use, limitations or failure response.
Testing does not prove the required operational function or remote indication.
Two matching screens are treated as independent although they share the same source.
A plausible false position is followed despite contradictory radar, depth or visual evidence.
AIS, ECDIS, VDR or time systems continue using suspect GNSS data without assessment.
Master's practical note
Ask which systems would be corrupted by one bad GNSS source. The response must cover the distribution network, not only the receiver showing the alarm.
Equipment boundary and references
Equipment boundary: Receiver capabilities and integrity modes vary. The passage plan must identify independent fixing methods and frequencies appropriate to coastal, ocean and interference-prone waters.
References
- OCIMF SIRE 2.0 Question Library Part 1, Version 1.0, Question 4.1.6
- SOLAS Chapter V regulations 19 and 27
- IMO Resolution A.1046(27)
- ICS Bridge Procedures Guide
- Receiver manufacturer instructions
Last reviewed: 2026-09-11
