Author Topic: GPS jamming?  (Read 2874 times)

GPS jamming?
« on: 23 February, 2023, 07:47:31 am »
Driving between Wolverhampton and Telford. Selected a destination in Telford on the car navigation. The system could not plot a route and after a time exited the route planning. Happened several times - I noticed that all Points of Interest were 1/2 mile away even though I knew they were over 10 miles away.
Could this have been selective GPS jamming or am I being too imaginative?

Re: GPS jamming?
« Reply #1 on: 23 February, 2023, 07:53:16 am »
I don't think GPS jamming would prevent the nav system from plotting a route, unless it didn't know your current location.
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Re: GPS jamming?
« Reply #2 on: 23 February, 2023, 08:04:16 am »
I have seen Google Maps do something similar occasionally on my Samsung phone and I have also seen run traces from my Garmin completely lose it and plot long, random straight lines cutting through buildings, crossing railways and canals where there are no bridges before hitting points sometimes miles away and then just as rapidly returning to the actual location.  I must be Superman 🤔 ...

Machines eh?  Minds of their own!

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Re: GPS jamming?
« Reply #3 on: 23 February, 2023, 09:06:31 am »
My old TwatNav, which lacked any of that real-time traffic information Stuffs, once decided that I should on no account be allowed to approach closer than ten miles to Des Moines IA* and kept trying to divert me into Children Of The Corn territory until such time as signs to the place were only visible in the mirror.  But she was perfectly OK with it on the way back ???

* I mean, it’s not as if Des Moines is twinned with Baltimore, Beirut or Birmingham.
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Re: GPS jamming?
« Reply #4 on: 23 February, 2023, 09:46:26 am »
If your current position or destination isn’t on a road, or rather if your software doesn’t think it’s on a road perhaps the navigation could fail?

For the POIs if you only had an approximate location that would explain why they appeared closer.

Re: GPS jamming?
« Reply #5 on: 23 February, 2023, 10:08:22 am »
I don't think GPS jamming would prevent the nav system from plotting a route, unless it didn't know your current location.

What do you think GPS jamming does?

Re: GPS jamming?
« Reply #6 on: 23 February, 2023, 10:10:08 am »
There’s a RAF base I sometimes pass and pretty much every time my Etrex has crashed when near the boundary fence. The unit just switches off, and first time I assumed batteries needed replacing.  But subsequent times I’ve turned it back on and it’s been fine, with batteries just dandy. It could of course been a mapping error causing it, but it’s occurred different places along the boundary.

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Re: GPS jamming?
« Reply #7 on: 23 February, 2023, 12:13:19 pm »
Occcam's razor suggests that errant behaviour by car TwatNavs is due to them being buggy piles of shit.

I can believe a zap from military radar causing a crash in something like an eTrex, but again, they're perfectly capable of crashing due to map problems (usually this freezes on the "GARMIN" logo), or switching off due to intermittent contact between the battery terminals and the PCB (my Vista HCx had this problem, easily rectified by application of solder).

I'd have thought if there was planned GPS jamming/spoofing going on, there'd be a NOTAM in place.

Re: GPS jamming?
« Reply #8 on: 23 February, 2023, 12:15:43 pm »
My  car's GPS always goes a bit awry on the M11 southbound not far below Duxford before correcting itself further down. Dunno why.
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Re: GPS jamming?
« Reply #9 on: 23 February, 2023, 12:18:39 pm »
My  car's GPS always goes a bit awry on the M11 southbound not far below Duxford before correcting itself further down. Dunno why.

Is it because it thinks you are exhibit escaping from the Imperial War Museum?  ;)
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Re: GPS jamming?
« Reply #10 on: 23 February, 2023, 01:14:35 pm »
Occcam's razor suggests that errant behaviour by car TwatNavs is due to them being buggy piles of shit.

I can believe a zap from military radar causing a crash in something like an eTrex, but again, they're perfectly capable of crashing due to map problems (usually this freezes on the "GARMIN" logo), or switching off due to intermittent contact between the battery terminals and the PCB (my Vista HCx had this problem, easily rectified by application of solder).

I'd have thought if there was planned GPS jamming/spoofing going on, there'd be a NOTAM in place.

Agree with the buggy pile of shit

Given that most aircraft will rely on GPS for their position finding I can't believe that anyone would turn on their GPS jamming gear unless the russian missiles were actually incoming.

My first satnav (garmin) had an interesting quirk that made it unable to plot a destination in one country if it had been in a different country when it was last turned off. Not very useful when you live near the England Wales border.
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Re: GPS jamming?
« Reply #11 on: 23 February, 2023, 01:20:57 pm »
Given that most aircraft will rely on GPS for their position finding I can't believe that anyone would turn on their GPS jamming gear unless the russian missiles were actually incoming.

Couldn't find any NOTAMs, but I did come across this: https://www.ofcom.org.uk/spectrum/information/gps-jamming-exercises

Which is the sort of thing you'd expect for planned testing of such equipment.

Of course, that doesn't preclude SEEKRIT military testing (though if it's mucking up people's satnavs it wouldn't stay SEEKRIT for long), J Random Squaddie accidentally pressing the wrong button, or some 1337 h4xx0r mucking about for the lols.

Re: GPS jamming?
« Reply #12 on: 23 February, 2023, 01:37:59 pm »
Yeah I remember sailing through a GPS jamming exercise off Scotland (It was heavily pubicised and a lot of people seemed to have sailed there that day for the lols) Our boats GPS ignored it.

The poster upthread was complaining that the GPS was borked every time he passed the airfield so unlikely to have run into a secret exercise - Maybe someone putting their coffee cup down on the control panel or some senior Rupert prodding random buttons and saying what does this one do?
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Re: GPS jamming?
« Reply #13 on: 23 February, 2023, 01:41:12 pm »
I don't think GPS jamming would prevent the nav system from plotting a route, unless it didn't know your current location.
This happened just after I started the car up.
My car is a Volkswagen - when new it would say it was in Wolfsburg if it could not 'see' any satellites. IT has had an upgrade since then and I haent seen it return to 'Home' at startup. But yes my suspicion is it could not determine position after switch on.

Kim

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Re: GPS jamming?
« Reply #14 on: 23 February, 2023, 01:44:03 pm »
The poster upthread was complaining that the GPS was borked every time he passed the airfield so unlikely to have run into a secret exercise - Maybe someone putting their coffee cup down on the control panel or some senior Rupert prodding random buttons and saying what does this one do?

Given the apocryphal stories of bored sailors microwaving seagulls with targeting radar, it doesn't seem improbable that the Biggles version can crash a piece of consumer electronics at a few hundred metres...

Kim

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Re: GPS jamming?
« Reply #15 on: 23 February, 2023, 01:49:03 pm »
I don't think GPS jamming would prevent the nav system from plotting a route, unless it didn't know your current location.
This happened just after I started the car up.
My car is a Volkswagen - when new it would say it was in Wolfsburg if it could not 'see' any satellites. IT has had an upgrade since then and I haent seen it return to 'Home' at startup. But yes my suspicion is it could not determine position after switch on.

Yes, it sounds like a perfectly normal cold start of the GPS chipset, which then diligently sits there and waits for the ephemeris data to arrive so it can work out where it is in time and space (which can take a great many minutes if it doesn't have a good view of the satellites).  Meanwhile the application software can either use some previous stored location for its route calculations (which may have been inadvertently hard-coded to default to Wolfsburg), or reaches some timeout waiting for the GPS fix, and gives up.

Why the GPS is cold-starting left as an exercise for the reader.

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Re: GPS jamming?
« Reply #16 on: 23 February, 2023, 02:05:31 pm »
Sounds like a device issue.  My previous one gave up the ghost as I was passing Stonehenge (spooky).  Although perhaps it was in shock that I only had a 5-minute delay in the A303-queue.  It was on the way to a B&B in the darkest Mendips, which meant finding my way (in the dark on a wet Friday night in January) was exciting.
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Re: GPS jamming?
« Reply #17 on: 23 February, 2023, 02:45:04 pm »
Amazingly I found my way to the hotel yesterday. By going back to the old methods - following road signs. I knew the hotel was at the International Centre so followed signs for there, and magically the hotel appeared.

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Re: GPS jamming?
« Reply #18 on: 20 March, 2023, 02:15:09 pm »
My car has built in sat nav but I tend to use Google Maps on my (work) iPhone, linked through to the car display via Apple Play. So far so good.

Occasionaly the Google Maps display glitches and has my position out by a couple of miles.  It did this a few weeks ago when I was driving home and kept trying to snap me to the roads nearest to where it thought I was.

Extra fun yesterday, driving through West Sussex, Google Maps up on the display but navigation mode not running. It had my position wrong, bumping across fields.  For added fun, I brought the in car navigation up. The car has two displays, one middle of the dash, which is where Apple Play puts the Google Maps display, and one infront of the steering wheel, where the speedo etc are situated, so both were visible at the same time. The weird thing was both the Google Maps display and the in car navigation had the same wrong position. The direction of travel was out too, by approximately 180 degrees.

After 20 minutes or so Google maps showed the correct position while the in car system still had me two miles adrift. 
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Re: GPS jamming?
« Reply #19 on: 20 March, 2023, 05:34:35 pm »
Cor, that's impressive.

Phones and to some extent cars aren't pure GPS receivers; they complicate matters by using the cellular network as a course positioning system and to augment the GPS fix, which is the sort of thing that must be an order of magnitude more likely to go wrong in interesting ways.

And that's before it tries to be clever by assuming that if you're a car you're driving on a road it knows about, possibly with the aid of dead reckoning based on wheel rotation.

And the afore-mentioned 'buggy pile of shit' problem.