GPS interference plaguing navigation in some regions, MarAd warns

GPS jamming sows confusion by disrupting navigational signals, while GPS spoofing takes that a step further by creating fake signals that could lead to vessel collisions. The majority of such incidents have been reported in the Mediterranean and Middle East.

Mariners should be on the lookout for significant Global Navigation Satellite System (GNSS) interference, especially in the eastern and central Mediterranean Sea, the Persian Gulf and multiple Chinese ports, according to recent alerts from the U.S. Maritime Administration (MarAd).

The interference has resulted in lost or inaccurate signals affecting bridge navigation, GPS-based timing and communications equipment. Satellite communications gear also may be impacted, the alerts said. In addition to the GPS system operated by the United States, GNSS includes Russia’s GLONASS and other regional navigational systems.

The most recent alert, valid through March 2021, reminds mariners to exercise caution when operating and prior to getting underway. The U.S. Coast Guard Navigation Center (NAVCEN) and NATO Shipping Center websites have published effective navigation practices for vessels experiencing GPS disruption.

NAVCEN asks mariners to report incidents in real time and to note critical information such as the location (latitude/longitude), date, time and duration of the outage or disruption. Mariners also are requested to provide photographs or screenshots of equipment failures to facilitate analysis. Incidents can be reported online ( via phone at (703) 313-5900, 24 hours a day.

NAVCEN recommends techniques in case of GPS interference, such as employing radar to mark bearings and distances on a paper chart (or switching to the dead-reckoning mode with a radar overlay on electronic charts) and using parallel indexing with multiple radars while underway. Situational awareness, including verified position and velocity, is crucial to maintain safe commercial operations, NAVCEN said.

The current MarAd advisory covers the entire world. However, the bulk of GPS interference incidents have been reported by vessels operating in the Mediterranean Sea, with a concentration in the vicinity of Egypt, NAVCEN reported. In the past several years, disruptions also have been reported in the Port of Shanghai.

GPS interference or jamming disrupts navigational signals in a given area, sowing confusion and leading to bottlenecks in ports and sea lanes. GPS spoofing creates fake signals that could lead a vessel off course. Terrorists could direct an oil tanker to crash, for instance, causing an environmental disaster.

Experts say it’s difficult to pinpoint the source of the disruptions. Sometimes they are due to atmospheric disturbances, technical causes such as equipment or mapping failures, or conditions in space. However, cyberattacks are strongly suspected in certain locations. Using a GNSS receiver on the International Space Station, researchers from the University of Texas at Austin pinpointed one source of interference from March 2017 through June 2020 at an air base in western Syria.

The first MarAd advisory of 2020 outlined commercial maritime threats from Iran and its proxies in the Persian Gulf, Strait of Hormuz, Gulf of Oman, Arabian Sea, Red Sea, Gulf of Aden and Indian Ocean. MarAd warned of the possibility of GPS interference, bridge-to-bridge communications spoofing and other communications jamming with little to no warning. Mariners also have reported bridge-to-bridge communications from unknown entities falsely claiming to be U.S. or coalition warships, according to the advisory.

With the realization that GPS and other electronics may come under attack in time of war, countries are looking to history for alternatives. The U.S. Navy has experimented with a World War II-era solution, dropping weighted message pouches from aircraft onto a ship’s deck. The Chinese military has trained to use bugle calls for battlefield communications if GNSS and radio signals become impossible to use.

By Professional Mariner Staff