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Comment by janoc | Hacker News Reader

Jamming GPS at an around an airport is not that great idea given that the airliners rely on it for navigation.

Granted, they have other means of navigating when the GPS isn't available but in the extremely busy airspace around London this would be just asking for a big problem.

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I don’t know much about GPS jamming, but I know a fair bit about how airliners navigate. GPS is usually not used for final approach, which is typically either visual or ILS (a radio signal transmitted from the ground). This in contrast to the earlier stages of approach which may use GPS depending on the airport and the specific approach in use. If you can keep the jamming signal contained to the immediate airport vicinity and a few thousand feet above, there should be little or no impact on (non-drone) aircraft navigation.

Truck driver uses a GPS jammer so his boss can't track him, then drives by Newark airport, disrupting their "Smartpath" precision navigation system.

Source: https://www.cnet.com/news/truck-driver-has-gps-jammer-accide...

Smartpath: https://aerospace.honeywell.com/en/products/navigation-and-s...

There are many more airports that have an RNAV GPS/GNSS approach procedure, than ILS. ILS requires expensive ground equipment, and fairly low obstruction clearance for miles surrounding the airport. I expect RNAV GNSS is used with some frequency at even big airports like Gatwick, on days when conditions don't require ILS in particular when the ILS is out of service for planned maintenance.

Example RNAV GNSS for Gatwick: https://opennav.com/pdf/EGKK/EG_AD_2_EGKK_8-4_en_2010-07-29....

But the airport was closed anyway. And there's some work by yours truly into targeted GPS spoofing, allowing not only to jam but also to take control of the device using GPS.

There are like 5 airports in London. You want to be pretty confident your jamming will be very local.

Yes, that sort of local. I'm not talking about kilometers, or even a whole airport. Something like 100m³ should be achievable without too much trouble.

I don't really want to link it to avoid linking this username to things, but I guess this should be okay: http:// rp dot delaat dot net/2017-2018/p95/report.pdf

There's actually only two "international" civilian airports in London.

London City, and London Heathrow.

Luton, Stansted, and Gatwick are "London" in name only. All about 30mins drive from the M25.

I can reach Gatwick in 30 mins from West London using an Oyster. That's faster than my commute into the City. So it's London, for all intents and purposes.

Isn't London City the only airport actually in London? See e.g. https://www.telegraph.co.uk/travel/news/heathrow-and-gatwick...

Heathrow and Gatwick are about the same distance from London City Airport.

How big is the area of a GPS jammer? Gatwick is 10km further out than London's biggest ring road and 45km from the centre.

> How big is the area of a GPS jammer?

However big you want to make it. All a “GPS jammer” is is a radio transmitting on 1575.42 MHz. Modeling the signal propagation of a transmitting device (Aka radio / antenna combo in this case) is a very very well known field.

A drone capable of jamming GPS in any useful area should carry a huge load of batteries to develop enough jamming power, not the best requirement for something strapped to a light flying machine where every gram counts. Anyone can buy a GPS jammer at the usual online stores, but they draw watts to cover an area of tens of meters, that is, to jam a single airplane you must fly the drone very close to it, and lose all other planes in the process. A flock of pigeons is many times more dangerous than a drone, even if carries a functioning GPS jammer.

To me any concern about GPS jamming is plain bullshit added to the soup to justify further restrictions on drone flying. Drones with cameras are powerful weapons these days.

>A drone capable of jamming GPS in any useful area should carry a huge load of batteries to develop enough jamming power

GPS is extremely low power and relatively speaking easy to jam. The received signal strength is far below the noise floor to begin with and it's basically RF black magic that it works to begin with. Those cheap GPS jammers that only radiate white noise at like a watt cause huge problems in the surrounding area.

There was even one case that I know of that would pertain to this subject in particular. A truck driver wanted to prevent his company from snooping on his whereabouts while driving a truck with a tracking system on it so he bought and used one of those cheap chinese jammers. He delivered stuff to an airport and just sitting in the parking lot was enough to keep aircraft from maintaining a GPS fix. There was also the case at Newark airport where just a truck driving by regularly was enough to cause problems.

And really those GPS jammers are the bruteforce and pretty ineffective approach. White noise is essentially what GPS is designed to work in, it just raises the noise floor 20 - 30 dB. GPS uses a gold code to transfer information and it's essentially looking for statistical deviations to be able to get a lock on such a weak signal. If a jammer was designed to be biased and transmit with the intention of preventing a receiver from being able to lock onto a satellite instead of just overpowering the signal entirely it could jam more with less power.

https://en.wikipedia.org/wiki/GPS_signals#Coarse/acquisition...

https://gizmodo.com/jamming-gps-signals-is-illegal-dangerous...

https://www.cnet.com/news/truck-driver-has-gps-jammer-accide...

I've never seen noise generators used as GPS jammers, that would be hugely inefficient. All boards I've seen so far, although not emitting a single frequency, jammed the target using sweep generators operating on the desired GPS frequencies. Some even do that simultaneously, which is why they use multiple antennas; if they transmitted noise they could do that using a single noise generator and a wide band antenna.

Example: http://jammergroup.quality.chinacsw.com/pz66df87e-handheld-6...

And by the way, Boeing had jamming resistant GPS back in 1998.

https://boeing.mediaroom.com/1998-04-23-Boeing-Anti-Jam-GPS-...

n00b question: are the GPS signals used by drones and commercial airliners the same? I know the military have their own special class of GPS.

Yes, same signal. The military signal you mention is military-only.

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