1. Reference: U.S. Maritime Alert 2017-005A.

2. Issue: During the week of June 19, 2017, multiple vessels operating in the Black Sea reported GPS interference, which included intermittent signals, no signals, or an incorrect signal. Both U.S. Maritime Advisory 2017-006, as well as U.S. Maritime Alert 2017-005A, advised mariners of this interference and provided guidance. This Advisory reaffirms that GPS disruptions are a global concern and provides amplified guidance.

3. Guidance: The U.S. Coast Guard Navigation Center (NAVCEN) recently posted information online regarding effective navigation practices in the context of GPS interference. The information reaffirms safe navigation practices when experiencing a possible GPS disruption, provides useful details in reporting a possible GPS disruption, and is intended to generate further discussions within the maritime community about other disruption mitigating practices and procedures. Further guidance includes recommendations to take note of critical information, such as the location (latitude/longitude), date/time, and duration of the outage/disruption as well as wherever possible, to provide photographs or screen shots of equipment failures during a disruption to assist analysts. The NAVCEN information is available at: http://mariners.coastguard.dodlive.mil/2017/09/21/9212017-good-navigatio....

4. Contact Information: GPS disruptions or anomalies may be reported to NAVCEN. Reporting a disruption, or other navigational hazards or aids to navigation outages to NAVCEN can be completed electronically through the following website: https://www.navcen.uscg.gov/?pageName=gpsUserInput or by phoning 703-313-5900, 24 hours a day.

5. Cancellation of Prior Advisories: This message cancels U.S. Maritime Advisory 2017-006 and will automatically expire on 20 June 2018.