Loss of DGNSS resulted in ROV being recovered – DP incident

Comments

Both the satellite positioning systems in use were from the same provider.
The report recognised this and recommended that the systems were changed so that position information was provided by different service providers. The service provider informed the operator after the event that its services experienced periods of increased latencies for just over twenty minutes on the day and time of the incident.

Considerations from the above event:

• It would appear from the information available that the standby hydroacoustic position reference (HPR) system did not have an acoustic transponder on the seabed. In any event it was not utilised.
• Proper consideration should always be made of the required PRS based on the specific operation and the DP equipment class of the vessel.
• When considering redundancy of satellite systems do not just consider equipment manufacturer and software versions; the correction type and transmission method should also be different.
• It is noted that two separate vendors could use correction details from the same source, therefore users should compare what correction type is being used.
• In similar situations users could consider switching to raw global navigation satellite system (GNSS) data, therefore staying on DP but with a larger footprint.