Web Alert: Master describes response to GPS denial incident in the Black Sea
22 September 2017
A recent blog post on the Coast Guard Maritime Commons site concerned a master’s response to a GPS outage which occurred in the Black Sea in June 2017. Multiple vessels transiting the North East portion of the Black Sea reported several instances of GPS interference. A master on one of the affected vessels contacted the US Coast Guard Navigation Centre (NAVCEN) to report the disruption. The blog post goes on to describe the actions taken by the master in response:
- setting the ECDIS to Dead Reckoning mode (DR mode)
- using the radar image overlay (RIO)
- comparing the ECDIS to paper charts
- parallel indexing techniques.
The master used the outline of the RIO to determine the error between the GPS position and the ship's actual position as defined by the radar. He then used this calculated error to add an offset to the ECDIS to marry up the two outlines, (RIO outline/ENC land outline). This information was then compared to the paper charts. Later, the master used parallel indexing techniques to navigate the vessel during the pilotage phase of the voyage.
Points to consider:
- The master in this instance was able to maintain situational awareness because he had sufficient knowledge of his systems. This knowledge should be acquired before an incident occurs.
- The master applied an offset to the ECDIS to marry up the RIO and the outline of the land on the ENC. Whilst this did provide the master with the situational awareness he required at the time, applying offsets to ECDIS equipment is not recommended. Some ECDIS have a drag and drop function which allows the user to pick up an ENC and drag it so that the land is aligned with RIO.
- The most effective and simplest means of maintaining situational awareness in the event of GPS failure is to apply a fix to the ECDIS using ranges or bearings. Every ECDIS is equipped with this function, but some brands are easier to use than others. When combined with DR mode it is possible to monitor the ships position in an effective manner.
In this instance, the actions of the master ensured that the failure of the GPS did not result in the failure of the voyage. The most effective means to deal with GPS failure is the use of manual fixing combined with DR mode. Every deck officer using ECDIS should be fully aware of how to use the ECDIS equipment in DR mode. This is especially true when the vessel is paperless.
Whilst the concept of DR mode is easily understood, it requires practice to master. Members should ensure that their deck officers are fully aware of the steps to take in the event of a GPS denial incident.
For full details of the incident visit the coast guard maritime commons.