GPS unavailability

[swill453]

An article on the BBC talks about a military exercise in Scotland coming up soon https://www.bbc.co.uk/news/uk-scotland- ... s-54264399

One part says

The Royal Navy said GPS services would be unavailable for limited periods during training in parts of Scotland's west coast.

So presumably with the cooperation of the USA they're switching something off so they can test how their equipment performs without GPS.

But how do they narrow the outage to such a specific area? As I understand it, each GPS satellite is broadcasting to a pretty wide area (33 satellites covering the planet according to Wikipedia). To switch off those covering the west coast of Scotland would surely wipe out coverage to a huge area?

Scott.

[XFool]

Might not be anything to do with turning GPS off. May it simply be GPS would be ineffective in some areas due to ground based RF interference?

[swill453]

Might not be anything to do with turning GPS off. May it simply be GPS would be ineffective in some areas due to ground based RF interference?

Good point, didn't think of that.

Scott.

[Infrasonic]

https://en.wikipedia.org/wiki/British_A ... on_systems

[swill453]

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

That page doesn't mention GPS, nor RF interference, so not sure how it helps answer the question. Is there something specific there you're pointing me to?

Scott.

[dspp]

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

That page doesn't mention GPS, nor RF interference, so not sure how it helps answer the question. Is there something specific there you're pointing me to?

Scott.

They are either experimenting with earth-based jamming/spoofing, or they are simply switching off the relevant satellites at source. Depending on satellite antennae design they may be directional, and if so they would be able to silence transmissions towards a piece of the earth whilst still keeping other areas live. I've not looked into the design of GPS / GNSS satellites in any great detail, but I suspect that is to an extent possible.

It is not just location signals that are affected, it is also timing signals. Both are equally important.

regards, dspp

[kiloran]

An article on the BBC talks about a military exercise in Scotland coming up soon https://www.bbc.co.uk/news/uk-scotland- ... s-54264399

One part says

The Royal Navy said GPS services would be unavailable for limited periods during training in parts of Scotland's west coast.

So presumably with the cooperation of the USA they're switching something off so they can test how their equipment performs without GPS.

But how do they narrow the outage to such a specific area? As I understand it, each GPS satellite is broadcasting to a pretty wide area (33 satellites covering the planet according to Wikipedia). To switch off those covering the west coast of Scotland would surely wipe out coverage to a huge area?

Scott.

Could it just be a poor choice of words?
I can switch off GPS on my phone, but of course that does not disable the satellites, it just disables the use of GPS by my phone. So maybe the military are just switching off the GPS functionality of their equipment to see how they manage without it.

--kiloran

[swill453]

Could it just be a poor choice of words?
I can switch off GPS on my phone, but of course that does not disable the satellites, it just disables the use of GPS by my phone. So maybe the military are just switching off the GPS functionality of their equipment to see how they manage without it.

I don't think so. I saw it because it was posted by the Cairngorm Mountain Rescue Team on Facebook with "Worth noting potential interruption to GPS positioning during this exercise."

Scott.

[UncleEbenezer]

Could it just be a poor choice of words?
I can switch off GPS on my phone, but of course that does not disable the satellites, it just disables the use of GPS by my phone. So maybe the military are just switching off the GPS functionality of their equipment to see how they manage without it.

I don't think so. I saw it because it was posted by the Cairngorm Mountain Rescue Team on Facebook with "Worth noting potential interruption to GPS positioning during this exercise."

Scott.

Had Cairngorm Mountain Rescue been officially notified? That would seem ... implausible.

Or had someone there speculated from hearsay information, such as what appears here? Is there any reason to suppose their information is any more authoritative than yours?

FWIW, GPS used to have a feature called "Selective Availability", that would degrade the signal (and the accuracy of any GPS fix) for anyone without crypto keys belonging to the US military. I think that was turned off many years ago: from hazy memory, the 1991 Gulf War was supposed to be a use case for it, but turned out to demonstrate uselessness instead.

[gryffron]

I suspect they could be jamming it. Plenty of kit capable of doing that over a reasonable area. After all, the bad guys can use commercial GPS too.

Gryff

[chas49]

It's jamming rather than switching off satellites

https://www.ofcom.org.uk/spectrum/infor ... -exercises