[SystemSafety] GPS jamming

Dewi Daniels dewi.daniels at software-safety.com
Fri Jul 12 12:18:30 CEST 2019


John,

I suspect it was a small aircraft with a GPS antenna stuck to the
windscreen, too. If that's the case, there is a safety issue of
over-reliance on uncertified GPS navigation devices. Many GA pilots find
software such as SkyDemon to be very useful. I have a Naviter Oudie IGC in
my glider, which serves a similar purpose. We know that GPS can be jammed
or spoofed. I've read a number of NOTAMs stating that GPS jamming trials
were being carried out at the Sennybridge ranges. The Oudie manual reads,
"Oudie is a personal navigation assistance device only. It is not a
replacement for any legally required device, method or service. User must
maintain all safety measures as if this device was not on board of the
aircraft". This does raise some interesting issues. If my Oudie reported
that I was 12 nautical miles away from my true position, I think I would
spot the discrepancy as I am flying VFR. If the Oudie reported that I was
100m away from my true position, it could mean the difference between
passing close to controlled airspace and infringing that airspace. Would I
be liable if I infringed that airspace even though I could produce an IGC
trace proving that my GPS reported that I was clear of the airspace? I
think I would still be liable. I doubt if I could detect a discrepancy of
100m, especially at altitude. I think the lesson is to stay well clear of
controlled airspace, even if my uncertified GPS device is reporting that I
am clear of the airspace.

I am puzzled by this incident. There isn't enough detail in the NASA
report. If the pilot was flying VFR, why did he not spot that he was 12 nm
away from his reported position? It suggests that he was just blindly
following the GPS. Would he be legally allowed to fly IFR with just a
vanilla GPS receiver?

Yours,

Dewi Daniels | Director | Software Safety Limited

Telephone +44 7968 837742 | Email d <ddaniels at verocel.com>
ewi.daniels at software-safety.com

Software Safety Limited is a company registered in England and Wales.
Company number: 9390590. Registered office: Fairfield, 30F Bratton Road,
West Ashton, Trowbridge, United Kingdom BA14 6AZ


On Fri, 12 Jul 2019 at 10:40, SPRIGGS, John J <John.SPRIGGS at nats.co.uk>
wrote:

> Hi Dewi,
>
> The original article does not tell us enough; if it were an airliner, it
> could not use ‘vanilla GPS’ and would have to have the RAIM capability
> mentioned in 1.7.1 of the document to which you linked.
>
> I suspect that it was one of those small aircraft that have a GPS antenna
> stuck to the windscreen, which can itself degrade the solution by occluding
> satellites.
>
>
>
> John
>
>
>
> *From:* systemsafety <systemsafety-bounces at lists.techfak.uni-bielefeld.de>
> *On Behalf Of *Dewi Daniels
> *Sent:* 12 July 2019 10:25
> *To:* The System Safety List <systemsafety at techfak.uni-bielefeld.de>
> *Subject:* Re: [SystemSafety] GPS jamming
>
>
>
> I'm puzzled. I thought the whole point of WAAS (and EGNOS) was that the
> pilot would be alerted if the GPS calculated position is inaccurate. See
> section 1.7.2 of
> https://www.gps.gov/technical/ps/2008-WAAS-performance-standard.pdf . Why
> was the pilot not alerted in this instance? Was he not using a WAAS
> receiver? If not, why was he relying on a vanilla GPS receiver for
> navigation?
>
> Yours,
>
> Dewi Daniels | Director | Software Safety Limited
>
> Telephone +44 7968 837742 | Email d <ddaniels at verocel.com>
> ewi.daniels at software-safety.com
>
> Software Safety Limited is a company registered in England and Wales.
> Company number: 9390590. Registered office: Fairfield, 30F Bratton Road,
> West Ashton, Trowbridge, United Kingdom BA14 6AZ
>
>
>
>
>
> On Wed, 10 Jul 2019 at 12:49, Robert P. Schaefer <rps at mit.edu> wrote:
>
> Thought this would be of interest:
>
>
>
> NASA report: Passenger aircraft nearly crashes due GPS disruption
>
>
>
>
> https://www.gpsworld.com/nasa-report-passenger-aircraft-nearly-crashes-due-gps-disruption/
>
>
>
> Along the lines of “Who the heck would jam GPS in the continental US?”,
>
> I’ve got an anecdotal story from one of Haystack’s scientists who was
> trying to collect GPS data
>
> (L1, L2 data is useful for measuring solar activity in the Ionosphere)
> during the solar eclipse in August 2017.
>
> He was unable to collect data because of GPS jamming. The story was that
> truckers use GPS jammers so they
>
> won’t be tracked by their employers.
>
>
>
> bob s.
>
> research engineer
>
> MIT haystack observatory
>
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