Comment by johansch | Hacker News Reader

Comment by johansch | Hacker News Reader

I experienced a very odd GPS failures about a week later (September 24) in south-eastern Sweden. At one point I was driving for about an hour (in quite isolated areas - around https://www.google.com/maps/@58.0381615,16.2094966,13.37z) without my iphone being able to get a gps fix. It's never happened before, or since.

The phone was fixed to the car's front window with plenty of sight towards the sky. I rebooted the device twice but it didn't help.

Our natural instinct here is to blame the russians for these kinds of things. At this time our biggest military exercise since the 90s was taking place in this region, with a lot of US involvement: https://en.wikipedia.org/wiki/Aurora_17

(One random theory: the russians were trying out some kind of remote, localized target GPS jamming tech. The GPS outage stopped once I got closer to the largest city in the region (150k people).

Additional rationale: If they unleashed GPS jamming signals that made hundreds of thousands of people lose GPS it would probably have made news. By localizing it to just affecting a couple of hundred people in isolated areas they would avoid that kind of mess.)

According to Washington Post, NATO officials said that at least one Russian ship with electronic warfare capabilities was in the Baltic sea during Aurora. American troops was stationed on Öland, close to where you were. Apparently it affected Latvian telephone networks as well.

There were plenty of signals intelligence planes in the air during the exercise, so it's a good bet that the jamming signals where both recorded and located, and that the information is secret.

https://www.washingtonpost.com/world/europe/latvias-cellphon...

I would assume the US/NATO also jams GPS/use some sort of scrambler for the unencrypted signal to have some military advantage...

Yeah, it's also possible that it was the Swedish armed forces/NATO doing the jamming as part of the exercise. In this case they would probably jam both GPS and GLONASS.

Seems politically quite risky though, what if some ambulance didn't reach their target or something like that? (Although I guess an easy workaround for that could have been tight coordination with the local rescue services - stop the jamming the moment there's an ambulance/fire emergency in the local area.)

Do ambulances typically operate at 2k-3k feet?

remote region ==> air ambulance?

I think the US military uses a different GPS signal that provides higher accuracy positioning.

The RF signal is the same, the additional accuracy comes from the use of cryptography.

The feature is called "Selective Availability", and has been disabled since May 2000.

https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...

So are you saying that the US military does not have a higher accuracy positioning system? I highly doubt that.

There are well-known ways to improve GPS accuracy, such as dGPS [1], inertial guidance, and beam-riding [2].

I think it unlikely that the US military has a secret second constellation of GPS-like satellites, operating on an undetectable secret frequency. Firstly, it would be difficult to launch and operate such a constellation in secret, and secondly, because augmenting the GPS data with independent, secondary sources operating with a different approach provides more redundancy and is proven technique for increasing accuracy.

The capability to limit accuracy in the satellite signal already existed – the fact that it was shut off is a strong signal that the perceived benefit is no longer important.

[1] https://en.wikipedia.org/wiki/Differential_GPS [2] https://en.wikipedia.org/wiki/Beam_riding

You are quite correct, notification of exercise-related jamming is published in NOTAMs at least here in the UK. For example for Exercise Joint Warrior 171 this year:

Q) EGPX/QWELW/IV/BO/W/000/400/5836N00447W135

B) FROM: 17/04/02 07:00C) TO: 17/04/02 17:00

E) GPS JAMMING WI 135NM RADIUS 583600N 0044630W (FARAID HEAD). USERS MAY EXPERIENCE ERRONEOUS PSN INFO OR DEFAULT DEAD RECKONING MODE. PERIODS OF GPS JAMMING WILL NOT LAST LONGER THAN 40 MINUTES AT ANY ONE TIME.

Cell phones don't use only GPS signals, they use "aGPS" which uses signals from cell towers to make the GPS calculations easier / faster. It's so effective in environments that the overwhelming majority of people spend the overwhelming majority of their time in that I think manufacturers don't include the very best GPS antenna, since they don't need to.

You say you were in remote areas, how was your cell signal during the time you couldn't get a GPS fix?

aGPS doesn't provide any useful positioning capability, it just speeds up downloading of the Almanac and Ephemeris which means the receiver doesn't have to listen to the GPS satellites as long before computing a position. You still need a good GPS signal for positioning to work.

The iPhone 4S and newer models also use GLONASS along with GPS for positioning. I suppose they could also encrypt their own system with a different scheme in unique situations.

(I was using an iPhone 5s.)

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