NAVIGATION
involved and others nearby reported GPS
jamming and outages. There was also an
abundance of smoke in the area along the
approach course to Friedman Memorial
Airport in Sun Valley, Idaho. The aircraft
was cleared for a GPS type of approach then
strayed off course at an altitude of 10,700ft
near a 10,900ft mountain. The report states if
the radar controller had not noticed and
intervened the flight crew and passengers
would have died.
Spoofing involves transmitting a signal
that allows a GPS receiver to calculate a false
position. A more sophisticated version,
known as smart jamming, is when a false
signal is transmitted that can’t be used by a
receiver to calculate a position at all.
Receivers in this case may continue to
function and not show they have detected
any fault. Russian use of jamming and smart
jamming was recounted in a report, “Above
Us Only STARS”, published earlier this year
by the Washington DC based NGO the
C4ADS group, which analyzes international
security issues.
The C4ADS report cites 10,000 Russian
GPS spoofing incidents detected over 2 years
affecting 1,300 ships in the Mediterranean,
Black Sea, Gulf of Finland and in the waters
off Vladivostok, Russia. Some of these
incidents near Russia and Syria occurred in
international waters and may be a
by-product of the Russian government
protecting Russian President Vladimir Putin
and other VIPs from drones.
The report also cites incidents discovered
by Professor Todd Humphreys of the
University of Texas in Austin. Humphreys
has devised a way to use sensors on the
International Space Station to detect and
record GPS signal disruption in real time.
Another report published last year by the
UK Government Office of Science, titled
“Time and Position: A Study of Critical
Dependencies”, found a growing dependence
on GNSS, including in aviation. The report
cites GNSS interference measured by two
sensors over four years. One was mounted
on the roof of a building in London’s
financial district and another near a
suburban airport where light aircraft use
GNSS to navigate. Both recorded around
four cases of interference every day, believed
to coming from road vehicles with jammers.
The report found that the vulnerabilities of
GNSS, both natural and man-made, are
poorly understood and that a backup system
is needed.
That report followed one published by the
UK Government in 2017, “The Economic
Impact on the UK of a Disruption to GNSS”
which estimated that a five-day loss of GNSS
would create a loss of £5.1 billion (US$6.4
billion). The report also shows that aviation
is only receiving about 1% of the £6.7 billion
(US$8.3 billion) worth of benefits from
GNSS, with roads receiving 49% and
emergency and justice services 30%.
“Now aircraft operators and airlines are starting to
pay attention to issues related to GPS outages”
Gerhard Berz, senior expert for navigation systems, Eurocontrol
42 AIR TRAFFIC TECHNOLOGY INTERNATIONAL 2020
Countering the threat
Civil aviation can be affected by jamming
that isn’t even intended to disrupt its
operations. Potential sources include GPS
jammers fitted to road vehicles and even
solar activity. In addition, nation states and
other groups that may want to disrupt civil
aviation can directly target aviation activities
and disrupt air navigation.
A solution proposed in the US to help
counter the threat to GPS is to develop an
eLoran (enhanced Long range navigation)
system. As a terrestrial based system
operating in a low frequency band, eLoran
would be almost impossible to jam or spoof,
according to Dana Gower, who leads the