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The U.S. military is testing a wide-area GPS jammers that could disable GPS satellite navigation signals from California into Mexico from the Oregon border during testing.

The tests were conducted on six Tuesdays and Thursdays this month, from 9:30 a.m. to 3:30 p.m. Pacific Daylight Time on June 7, 9, 21, 23, 28 and 30 - has the potential to disrupt satellite navigation on commercial airliners flying to and from busy ports of entry on the West Coast, such as Los Angeles International Airport, and San Francisco.

During these times, commercial and general aviation aircraft may need to revert to older air navigation systems, including VHF and IF radio beacons that send signals to cockpit avionics known as VHF full range (VOR) indicators and automatic direction finding (ADF).

On six days this month, Federal Aviation Administration (FAA) officials issued flight notices (NOTAM) to pilots warning of possible GPS interference on planes.

• The FAA warned that the military tests, conducted at the China Lake Naval Air Warfare Center in the desert town of Ridgecrest, California, "may result in unreliable or unusable GPS signals."

• During tests in areas including major airports in Los Angeles, San Francisco Bay, San Diego, Phoenix and Salt Lake City, the GPS signals of aircraft flying at an altitude of 25,000 feet could be interfered with or lost.

• It is not just air navigation that is affected. Land vehicles, ships and surface vessels could degrade GPS capabilities within 235 nautical miles of China Lake, which includes the ports of Los Angeles, Oakland and San Diego.

Details about the military GPS jamming test are scarce, but it begs the question: What's worth eliminating GPS navigation in more than half of the West Coast's major metropolitan areas?

1. There is a very real threat that electronic warfare interference could disable large areas of satellite navigation. The potential impact of GPS interference is not yet widely known, but the more we rely on GPS, the more serious the threat becomes.

2. Twenty years ago, no one seriously thought about GPS. Today, it has become standard on all smartphones. I know a lot of drivers who can't live without it. Today, learning to use the old Rand McNally Road Atlas is no longer a priority.

This fall, amid suspicions that Russia is jamming GPS signals in Europe and elsewhere, the U.S. military will test an anti-jamming GPS in an attempt to solve the "breakout defense" problem.

GPS jammers could also become a major liability for the United States and its Allies, with systems that rely on them for everything from troop movement to missile and drone guidance. Last fall, the United States and NATO Allies launched a major joint exercise called Trident Junction in Norway to test the joint readiness and training of the large multinational alliance. During the exercise, the military noticed GPS signals were jammed, which Finnish and Norwegian officials blamed on Russia. In April 2018, U.S. officials said the Russian military had interfered with the GPS systems of its drones operating in Syria.

Members of the 2nd Cavalry Regiment in Germany will receive the jamming device this fall, and the military is reportedly looking to develop a new generation of inertial navigation systems that can be used as a backup.

The United States, Russia, China and other countries are developing new weapons to compromise other countries' satellite constellations. Anti-satellite weapons can not only degrade a military adversary's ability to operate on the battlefield, but also threaten civilian use in space. This makes it more difficult to identify a single perpetrator of an attack and could deal a serious blow to the military and economic power of space powers in both peace and war.

At the same time, Russia is investing in near-Earth anti-satellite capabilities, deploying satellite jamming systems to disrupt data flows between satellites and their customers on the ground. The Center for Strategic and International Studies (CSIS) noted that there have been multiple reports of GPS interference in and around Russia, as well as Russian forces in Syria. The outage of GPS makes it harder for pilots and homing weapons to quickly reference their position. Forms of interference include cell phone jamming GPS signals, preventing users from accessing data, spoofing locations, and secretly sending false location data.

China is also working to develop ground-based gsm jammer to disrupt satellite data transmissions, an important capability that could be used against long-range adversaries such as the United States.

Perhaps the most advanced anti-satellite weapons program of any country is run by the United States. The U.S. military has a powerful Arsenal of anti-satellite weapons, including ground-based interceptor missiles deployed in Alaska and Hawaii. The GBI was originally designed to shoot down ballistic missile warheads aimed at the United States through low-Earth orbit. The U.S. Navy's SM-3 interceptor missile has more experience in this regard, having shot down an aging satellite during Operation Frost Burn in 2008.

Unintentional interference from radio and space can cause problems for GPS systems, as can GPS interference and deliberate signal spoofing. But according to a 2012 Homeland Security report recently released under the Freedom of Information Act, communications companies are not ready to protect GPS systems from these threats, EE Publishing reports.

The communications industry is "vulnerable to a potential prolonged GPS outage" lasting a few days or more, which "could result in a reduction in service quality across the industry," the report said.

If you rely heavily on GPS, then your confidence is likely to be lost - and that's just to find a friend's home, restaurant, or the latest trendy bar.

Experts are beginning to study the resilience of global Positioning System (GPS) satellite navigation networks to the effects of intentional or unintentional electronic interference. The reaction was not very good.

Radio frequency and microwave experts at Crowley Bollen Communications in the UK have been studying electronic interference in GPS signals for a year and have come to some surprising conclusions.

"We have searched the world for GPS interference and found many incidents of interference, some of which were intentional," said Guy Buensel, PNT technology specialist at Spirent, a multinational telecommunications test and measurement company.

If the reliability of automotive GPS systems is questionable, what are the implications for commercial air traffic control, radar systems, intelligent munitions guidance, or fleet management of trucks and cargo ships?

After a year of GPS testing, Spiellen concluded that satellite navigation signals are subject to a variety of disturbances that can damage, weaken or eliminate GPS signals during one-time temporary events.

These temporary GPS outages can cause more problems than meets the eye. The reason for this is that ground-based GPS users rely as much on timing services as they do on location information. GPS satellites are equipped with precise atomic clocks that provide unprecedented timing accuracy.