GPS Jamming Exercise at Portreath

[Roadster280]

TMI - I'm not GPS expert, but it would surprise me if a military system had no ECCM capability by design. Perhaps it's not in the public domain, even if it did.

The other thought I had is in response to the question, why the enemy would want to jam it at all, since it would be useful to them too. Why not introduce a widely variable (10s of km) error, but have the error factor known to own forces? Nice bit of disinformation warfare. Much more sophisticated than jamming.

I believe we retired our (ground) jammers, because they were as useful as a 10MT nuclear warhead on the tactical battlefield.

[Pontius Navigator]

Roadster may I refer you to the GPS used by the crew on the HMS Cornwall Lynx. This is identical to the one I bought on eBay and have in my drawer. The one in my office is made by the 'other' manufacturer, is in a fetchind shade of green, has a lot of numbers on it and is decorated with a stylish NATO logo. It is no different from a commercial product.

There are other comments that I might make but I believe I got that information from protected sources.

What you might deduce from what I said is that there are GPS and GPS.

Remember too that GPS is a proprietary name whose full name is Navstar GPS. It is the US owned Global Navigation Satellite System. This link gives some useful background and the bit on Selective Availability is relevant.

http://en.wikipedia.org/wiki/Global_Positioning_System

There is a rival Russian system, GLONASS, with about 14 funtioning satellites:

http://usinfo.state.gov/xarchives/di...ellep0.5061609

There is then a possibility that the European system Galileo will become operational too.

http://www.military-geospatial-techn...cfm?DocID=1379

I believe the Chinese have bought in to Galileo.

With 3 available systems and multi-channel capable receivers an exo-atmospheric nuclear burst would provide a 100% ECM solution. For local GPS denial you would need a battery of jammers to cover each satellite frequency and system.

[Roadster280]

PN - Thanks. I believe you have corroborated what I was trying to say, without saying it.

HMS Cornwalls' GPS has had plenty of press, in any case!

I honestly know bugger all about GPS in practice, but I do know a thing or two about mil radio systems in general.

Q. Why would an exoatmospheric nuclear detonation cause global system outage? Surely only those birds within range would be toast, those on the dark side of the "extra sunshine" could survive, and (less any EMP effects) continue? As I said, I know bugger all about GPS, are there not enough birds?

[Pontius Navigator]

I believed the exoatmospherics affected propagation and was not intended as of itself to destroy anything. You are right that constellations in sight of the burst would be toast. However this link http://www.studycommittee.org/high-a...ear-tests.html it tells how satellites entering the burst area where also destroyed.

It is possible that improved techniques have been developed to harden the satellites. http://stinet.dtic.mil/oai/oai?&verb...fier=ADA254944

[ORAC]

The other thought I had is in response to the question, why the enemy would want to jam it at all

Well, knowing we have GPS guided bombs, rockets n'all, I'd be tempted to jam it whenever we we were under attack, and sod anyone else who got screwed up.....

[Pontius Navigator]

ORAC there is also the potential for seduction. For instance what better way to get a couple of rigid raiders an an ipod?

[Roadster280]

ORAC - Quite true, but so do the (conventional) enemy. Hence my suggestion of surreptitiously spoofing the output.

[WE Branch Fanatic]

Are you forgetting the difference between P code and the C/A code (which use different frequencies)? The latter is freely available via the open market, which means anyone can build it into weapons - hence the possible need to jam. A low power transmitter feeding false data could totally corrupt systems using the C/A code. Of course you could just transmit noise, but since the GPS reciever extracts the signal from noise it may be hard to fool if the signal doesn't look right (it knows what the GPS signal looks like, and correlates this against the noise to extract the signal buried within it - so jamming it with white noise won't achieve much).

[Pontius Navigator]

WEBF, mm, that would explain why the RN, on such an important mission used a cheap commercial GPS?

[RODF3]

The other thought I had is in response to the question, why the enemy would want to jam it at all, since it would be useful to them too. Why not introduce a widely variable (10s of km) error, but have the error factor known to own forces? Nice bit of disinformation warfare. Much more sophisticated than jamming

Nice idea, but unless the error changed randomly, all you would have to do to counter is go to a known location and measure the difference.

[Wader2]

RODF3, very true and indeed we do that already. DCRE set up some datum marks using a DGPS. We then check the hand-held against the datum and apply corrections.

Interestingly the Garmin, as used in Iran, has the ability to set a datum height. This, as advertised, improved its accuracy. My earlier Magellan did not have that feature.