GPS antenna problems
- Safety Flash
- Published on 9 June 2008
- Generated on 13 June 2026
- IMCA SF 10/08
- 2 minute read
A Member has reported a serious failure of a vessel’s GPS positioning equipment.
What happened?
When approaching the work area, which was close to the shore, the vessel experienced a complete failure of all its GPS receivers (eight receivers from four different manufacturers/suppliers).
Following extensive fault-finding which isolated the problem to the area of the vessel bridge, it was discovered that one GPS unit was causing the failure of all the other units. The receiving antenna for the unit had failed and had become a transmitter, the signal from which subsequently blocked all the other GPS receivers mounted nearby. The close proximity (<1m) of this damaged antenna unit to two other GPS antenna units may also have caused damage to the internal electronics of these units.
Recommendations
Members are warned to be aware of the potential hazard posed by a faulty GPS antenna and that all GPS antennae be separated by at least two metres where possible. It is recommended that when selecting the mounting location and installing global navigation satellite system (GNSS) antennae, guidance is taken from the system manufacturer with regard to safe operating distance from other equipment and with special attention given to transmit/receive devices. Care should also be taken in the selection of appropriate cabling and antennae and to the shielding and grounding required for these systems. A regular inspection and maintenance schedule is also recommended, with periodic replacement of cables.
IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of the entire offshore industry.
The effectiveness of the IMCA Safety Flash system depends on the industry sharing information and so avoiding repeat incidents. Incidents are classified according to IOGP's Life Saving Rules.
All information is anonymised or sanitised, as appropriate, and warnings for graphic content included where possible.
IMCA makes every effort to ensure both the accuracy and reliability of the information shared, but is not be liable for any guidance and/or recommendation and/or statement herein contained.
The information contained in this document does not fulfil or replace any individual's or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.
Share your safety incidents with IMCA online. Sign-up to receive Safety Flashes straight to your email.