[Paddlewise] NTSB & USCG on GPS

from USCG district 5 Local Notice to Mariners:

NATIONAL TRANSPORTATION SAFETY BOARD ON GPS The National Transportation
Safety Board (NTSB) has issued an Urgent Class I Recommendation to the
U.S. Coast Guard following the grounding of a cruise ship. The
recommendation included a request to advise mariners of the possible
safety problems associated with Global Positioning System (GPS)
receivers which automatically revert to dead reckoning (DR) tracking
when satellite fixes are not received for a period of time.
In the case prompting this advisory, it is believed a cruise ship ran
aground due to an antenna failure resulting in the loss of satellite
signals. This reverted the GPS to use positions based on DR tracking as
input to the autopilot. Alarms indicating the receiver was in the DR
mode were not heard nor detected visually, which led to a course error
of 14 nautical miles. This casualty was preventable by personnel.
Vessel operators are advised of this circumstance and are urged to
review the design of their bridge systems to identify potential system
and operational failure modes that might result in undetected changes to
the autopilot function and develop modifications as required.
Additionally, bridge officers are reminded not to rely on any single aid
to navigation, but to use all navigation resources at hand.

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