This incident summary is based on a safety alert issued by the Marine Safety Forum concerning the loss of Differential Global Positioning System (DGPS) signal in offshore operations in the Persian Gulf. The report includes details on the operational impact, possible contributing factors, and immediate corrective measures taken.
What Happened
An offshore operator reported DGPS signal loss in the Persian Gulf, suspected to be linked to ongoing military activity in the Middle East. The disruption prevented vessels from meeting the minimum number of position reference systems (PRS) required for dynamic positioning (DP) station keeping. From 13 June, all contracted DP2 offshore support vessels experienced DGPS outages, resulting in the temporary suspension of DP operations. The signal loss was widespread in the region and impacted normal DP operations, with the potential to disrupt offshore supply activities. Instructions from DGPS service providers were followed, but the problem persisted. Helicopter operations offshore were unaffected.
Why It Happened
The probable cause of the DGPS signal loss was electronic interference linked to heightened military activity in the region. Reports from monitoring authorities indicated increased interference within the waters of the Gulf and the Strait of Hormuz, significantly affecting vessel positional reporting via automated systems such as AIS. This interference compromised the ability of vessels to maintain accurate positioning for DP operations.
Actions Taken
Operations within the 500-meter safety zone were suspended in accordance with Activity Specific Operating Guidelines (ASOG). A joint risk assessment was conducted between the marine team and the vessel’s technical operator to assess operations using only two PRS without DGPS. The marine risk team subsequently reviewed the situation and developed an interim ASOG, which was successfully trialled for cargo operations offshore.
Lessons Learned
- Maintain readiness to operate with alternative PRS configurations in case of DGPS failure.
- Conduct thorough joint risk assessments before resuming operations with reduced positioning capability.
- Develop and trial interim operating guidelines to maintain essential offshore activities safely.
- Monitor and report electronic interference promptly to relevant authorities.
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Source: Marine Safety Forum
