GPS Jamming

bilbobaggins

bilbobaggins

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At an RIN R&D Group Symposium last week, top UK security experts outlined how vulnerable the GPS L1 and L2 signals are to jamming - both inadvertent and deliberate. OFCOM apparently hunt down inadvertent 'foul-ups' caused - usually - by harmonics ( one elusive example was a low-voltage light bulb ), while other 'gorillas' in their employ liaise daily with heavyweight anti-terrorist and contra-organised crime outfits. They're hoping shortly to deploy 1000 remote RF monitors around the country. Serious stuff!

It seems that small but effective jammers have been on sale for years - e.g. at the Paris Air Show - and plans complete with parts lists are available on the internet. So also is pirated GPS pseudo-code, apparently. Why would anyone bother? The answer was "Consider computer virus writing. Just because they can...!"

The present satellites transmit at the equivalent 'of a 40-watt light bulb at 7000 km.' and 'you generate more energy stroking the cat', so it's easy for a functional device on a hilltop, powered by a car battery, to swamp the proper signal over areas of hundreds of square kilometres.

This is one of the primary reasons why GPS is not approved as a Sole Aid To Navigation where Safety of Life is an issue. The new 'Galileo' system will do better, allegedly. If you want more 'scuttlebut' on this, or wish to quibble, see here:

RIN home page

BTW, the RIN has been running an excellent and well-attended series of symposia up and down the country, jointly with the Royal Met Society, on 'Weather and Sailing'. Worth every penny.....

I think I'll dig out my pencils and old black-and-white charts again.....

/forums/images/graemlins/shocked.gif /forums/images/graemlins/shocked.gif
 
Yes GPS signals are very low level signals when received on earth. The signals from TV, radio and phones are far higher. The signal processing to extract the GPS data from these low level signals is mind blowing.
Yes GPS is very vulnerable. The only good thing I suppose is the chances of sufficient jamming signal reaching where you actually are quite low.
 
it's very very easy to jam a gps, you can by GPS jammers in russia. - But if you get cought, you will do about 5-10 years inside.
 
Basic premise of one of the IMO better Bond films.

Valid point may be that if it is _that_ easy it might be commonly encountered in places ending in -istan...

The Press would be on that one unless its been really well hushed up, or has not been a serious issue, which it presumably hasn't, otherwise RIN would not have been allowed to discuss it. But still an interesting issue.
 
I suspect that the far greater risk is forumites jamming their own GPS's through bad electronics and radio installations on their boats /forums/images/graemlins/smile.gif.

John
 
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[ QUOTE ]
I suspect that the far greater risk is forumites jamming their own GPS's through bad electronics and radio installations on their boats /forums/images/graemlins/smile.gif.

John

[/ QUOTE ]

too true - the first law of management "incompetence is always more likely than conspiracy"
 
Re: GPS Jamming - alternatives?

Assuming you have a sextant and a watch on board but don't know how to use the sextant, what is the best book for learning from scratch when the GPS packs in?

- Nick
 
Re: GPS Jamming - alternatives?

Tom Cunliffe's Ocean Sailing is an excellent book for astro navigation, Fernhurst ISBN 1-898660-61-1 about £14 or so.

I have produced a simple backgroung do the concept which, if you or anyone else would like a copy, send me an email and I will blast it to you.
 
Re: GPS Jamming - alternatives?

[ QUOTE ]
Assuming you have a sextant and a watch on board but don't know how to use the sextant, what is the best book for learning from scratch when the GPS packs in?


[/ QUOTE ]

You shouldn't wait until the GPS packs it in before you try to figure out the sextant from scratch. /forums/images/graemlins/wink.gif

Kevin
 
Re: Sextant as an emergency backup

Erm . . . . yes, of course, it would be nice, assuming no other demands on time and a suitable teacher available to help.

However, as a 'better than nothing' approach the concept of the sextant as an emergency backup doesn't seem too stupid, and there used to be an 'emergency sextant book' which had step by step idiot proof instructions plus almanac plus sight reduction tables, but the tables expired in 2004 and I don't think the book was republished.

Cunliffe, Blewitt et al insist on explaining the theory in considerable detail - all that is required for emergency use is a step by step guide to the mechanics, not an understanding of what is involved.

Nearest thing I have found currently available is THIS , but it doesn't say when the tables go up to . . .
 
Re: Sextant as an emergency backup

We lugged ours around all last year - might have taken it out the box and played with it about twice. Still worth while just to feel "familiar" with it.

Serious suggestion: before getting into noonsights and celestial navigation, why not get the feel for it in coastal navigation - measuring horizontal angles for "distance off" and position calculations. Just as easy as compass bearings, and one helluva lot more accurate. More likely to be spot on rather than a huge cocked hat.
 
Re: Sextant as an emergency backup

I agree, it's a vastly underrated aid to coastal nav. Even better if you have one of those 3 legged plotter thingies for fixing with 2 horizontal angles.
 
Re: GPS Jamming - alternatives?

This is fundamental to our coastal navigation training. Always has been.

There are three 'legs' to the marine navigator's 'stool':

1. Electronic quick fixing ( GPS, radar, Loran, Decca, Consol, etc., - and what to do with the info )

2. Visual slow fixing ( Lines of Position worked into fixes e.g. HandBearingCompass bearings; echo sounder readings; transits natural and artificial; range position lines from coastal use of sextant; range position lines from offshore/ocean use of sextant - and what to do with the info )

3. Deduced reckoning ( EP from course steered and distance run, with estimated tidal influence and leeway - and what to do with the info )

These modes are intended to be hierarchical and reversionary - as one becomes unavailable, you switch into the next best mode, with appropriate change of wariness. Natch', you need to record the info you get as you progress along ( log-keeping ), 'cos you don't know when you'll suddenly be dropped into a reversionary mode.

Use of a sextant - along the coast and/or in deep ocean - is simply an example of the second mode.

This is navigation at its simplest - as understood and practised worldwide. Now, that's what the RYA's Dayskipper Course is supposed to teach you. If you didn't come away with that, go and ask for your money back!

There are several excellent books that will help with these concepts. Tom Cunliffe's are favourites of mine, as are Tim Bartlett's, 'cos peeps seem to like the clarity. Link those to the RYA's excellent Course Notes booklets ( simple aides-memoire ), with the RYA's Book of Navigation Exercises plus a good 'mentor' to help out when a concept doesn't quite come into focus, and you'll be well equipped to take marine nav in your stride.

If that helps, it's a pleasure. If you want something more specific, PM me with details and I'll try to point you in the right direction.
 
Re: GPS Jamming - alternatives?

Erm . . .

Not quite sure why you have decided to give me a lecture on the basic principles of navigation . . . I have a YM with commercial endorsement and am a Cruising Instructor so am qualified to teach practical courses to Day Skipper level.

Many Yachtmaster Instructors (offshore, not ocean) are unable to plot a fix using astro-nav, although they may be proficient at using a sextant for other purposes (e.g. calculating distance off, which is a simple procedure even for the navigationally challenged).

I have a sextant, understand how it works but have never had the time / patience to teach myself astro nav. A complete GPS failure (of three independent units) on an ocean passage would concentrate the mind wonderfully, and with plenty of time in hand I have no doubt I can master the black art. Astro is more and more being seen as an EMERGENCY navigation procedure - reversionary in your terms - and many yachtsmen carry a sextant purely as a back-up, along with tables and a basic instruction book.

Please don't patronise me . . . hopefully it was unintentional.

- Nick
 
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