Jun 112008

Comfortable that having eight GPS receivers from four different manufactures aboard will make sure you know where you are? Don’t be complacent is the message in the latest safety flash from the International Maritime Contractors association, IMCA.

One would expect a GPS antenna failure to just result in a lost signal, but it could result in the receiver becoming a transmitter and knocking out the other GPS units. An IMCA member reports that 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.

The seriousness of the failure is self-evident. Be aware of the potential hazard posed by a faulty GPS antenna and that all GPS antennae should be separated by at least two metres where possible.