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Old 01-08-2013, 05:58   #61
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Re: Dust Off Your Sextants! GPS Hacked!

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Originally Posted by captain58sailin View Post
When ever the military is about to embark on an operation, they introduce a GPS error, to keep the opposing forces from working effectively. We really don't need the computer nerds monkeying with the system.
Atually in the first gulf war they did the oposite. Made the civilian GPS more accurate by removing selective availability (SA). This because they had a shortage of military GPS-es and suplemented them with civilian ones.
SA has been turned of in 2000, as far as I know for good.
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Old 01-08-2013, 06:05   #62
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Re: Dust Off Your Sextants! GPS Hacked!

That wasn't the case off the coast of Somalia during the late unpleasantness in the early 90's.
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Old 01-08-2013, 06:33   #63
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Re: Dust Off Your Sextants! GPS Hacked!

Those of us that started cruising before GPS was introduced remember what an incredible change it was.

SA was a serious drawback,however. SOG fluctuated making current calculating almost useless and there was little point setting an anchor alarm.

What is not well appreciated, and deserves comment among the doom and gloom, is the GPS has been getting steadily better since then. The number of functioning satellites is higher and the GPS receivers have got much better.
Try things like an anchor alarm and without any multi path distortion the system achieves amazing accuracy especially if you can get a SDFix.
Have a look at the tight plot of this trace over 24hrs.

I think some members secretly long for a return of the days when men were men and they bravely navigated with a sextant and a prayer. All that experienced those days feel differently.
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Old 01-08-2013, 06:45   #64
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Originally Posted by captain58sailin View Post
When ever the military is about to embark on an operation, they introduce a GPS error, to keep the opposing forces from working effectively. We really don't need the computer nerds monkeying with the system.
Actually they don't
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Old 01-08-2013, 07:56   #65
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Re: Dust Off Your Sextants! GPS Hacked!

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Currently we have GPS , GLONASS, and Galileo ( in slow startup) with two more proposed systems. In future that's a awful lot of systems to go down. You might as well say , loose the global telephone network.

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Old 01-08-2013, 07:59   #66
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Re: Dust Off Your Sextants! GPS Hacked!

"Currently we have GPS , GLONASS, and Galileo ( in slow startup) with two more proposed systems. In future that's a awful lot of systems to go down. You might as well say , loose the global telephone network. "
Arguably hard for some jihadi or robber to take out but is it a lot to go down?

Consider. Galileo, not here yet, depends on a consortium funding it. GLONASS? Depends on Mr. Putin and more politics, more likely to stay up but those ARE the same folks who put on a poker face and moved whole cities and mountains on their official maps. And if their borders with China get hot, as they have before, GLONASS would be likely to be manipulated to deny it to the Chinese.

Then there's all three anyway...but rogue states are launching satellites, and all it takes to destroy existing ones is a handful of buckshot thrown into orbit in the opposite direction. Literally. Ignoring the Chinese, who shot down a "weather" satellite and created a debris cloud...one rogue state, one good launch, I'd guess they could take out four to six satellites and put a large hole in the systems. Or, just launch one, with a couple of jammers on it, and put everyone out of commission for a while. For obvious reasons, no one will comment on whether we have antiradiation missiles or satellites up there to stop that scenario.

More likely, once GPS-assisted precision landing and routing is allowed for our airlines, someone will wait for that to become mainstream, and then pull down a jumbo jet on landing. That's when you'll see "surprise" and calls to harden the systems against hacking. One jumbo, landing, splashed into a major urban area.
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Old 01-08-2013, 08:05   #67
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Re: Dust Off Your Sextants! GPS Hacked!

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Originally Posted by captain58sailin View Post
That wasn't the case off the coast of Somalia during the late unpleasantness in the early 90's.
Quite possible. But on my calendar the early 90's predate may 2000
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Old 01-08-2013, 08:12   #68
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Re: Dust Off Your Sextants! GPS Hacked!

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Then there's all three anyway...but rogue states are launching satellites, and all it takes to destroy existing ones is a handful of buckshot thrown into orbit in the opposite direction.
Getting something in a retrograde orbit is not that easy...

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Literally. Ignoring the Chinese, who shot down a "weather" satellite and created a debris cloud...one rogue state, one good launch, I'd guess they could take out four to six satellites and put a large hole in the systems.
OTOH, the Chinese economy itself is very dependent on GPS as well. Everyone is. Taking out GPS will harm the perpetrators as well. But then, only idiots wage war on the US. And the Chinese aren't idiots.

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More likely, once GPS-assisted precision landing and routing is allowed for our airlines, someone will wait for that to become mainstream, and then pull down a jumbo jet on landing. That's when you'll see "surprise" and calls to harden the systems against hacking. One jumbo, landing, splashed into a major urban area.
You can be sure that GPS assisted precision landing will not be permitted before this issue is solved.
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Old 01-08-2013, 08:14   #69
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Re: Dust Off Your Sextants! GPS Hacked!

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Originally Posted by noelex 77 View Post
Those of us that started cruising before GPS was introduced remember what an incredible change it was.

SA was a serious drawback,however. SOG fluctuated making current calculating almost useless and there was little point setting an anchor alarm.
I did some measurements in the early 90ies on a stationary receiver. I must still have the plots somewhere... The results were interesting. The 95% ellipse was about 100m long on it's longest axis.
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Old 01-08-2013, 09:43   #70
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Re: Dust Off Your Sextants! GPS Hacked!

I have noticed that the quality of GPS accuracy does take a noteworthy departure in areas of military operation when things are going on, but it's never been enough to make me worry about being able to navigate a boat effectively. There were deviations of around 100 yards when military jets were flying over the beaches near Aviano. That's not going to make you miss an Island or even hit the wrong harbor. It's just going to make you need to watch the channel markers. If that is the worst thing that happens all day, I will still choose to call it a good day.

99.9% of the time, GPS gives me better accuracy than specified. I normally operate within a 30-foot circle of uncertainty, but actually observe genuine inaccuracy of 6-feet or less. I still keep some form of backup navigation available, but I almost never look at anything else, other than a compass or a physical mark.
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Old 01-08-2013, 10:33   #71
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Re: Dust Off Your Sextants! GPS Hacked!

The US Governments position on selective availability

http://www.gps.gov/systems/gps/modernization/sa/l

The US and cooperation with other nations

GPS.gov: International Cooperation

The US does, however, have a second coded gps signal for its military.
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Old 01-08-2013, 10:43   #72
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Re: Dust Off Your Sextants! GPS Hacked!

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Originally Posted by hellosailor View Post
Which also makes your signal the highly visible target for the "antiradiation" missile that someone is going to fire, to take out the spoofing source if it runs for any length of time.
Do I have to declare these missiles in every port?

Where can I buy one? Should I stow it with my anchors and guns?
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Old 02-08-2013, 00:44   #73
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Re: Dust Off Your Sextants! GPS Hacked!

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The US does, however, have a second coded gps signal for its military.
One of the things we did when I was a student was record the military signal, and then use that for accurate positioning, accurate to a few millimeters. This was only possible through post-processing though. Quite handy for surveying, but useless for navigation. I guess the military didn't care...

I believe the new generation of GPS satellites doesn't even have the SA facility anymore, but does have a third military signal that is even harder to spoof.
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Old 02-08-2013, 04:45   #74
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Re: Dust Off Your Sextants! GPS Hacked!

The GPS system, is just that a system, The C code is needed to establish a fast fix for the encoded P code, so both are needed.


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Old 02-08-2013, 08:50   #75
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Re: Dust Off Your Sextants! GPS Hacked!

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I think read somewhere on one of my old, musty paper charts: The prudent mariner shall not rely solely on any single aid to navigation....
I maintain that is still relevant and sensible advice, and that fewer sailors would find themselves in unhappy circumstances if they heeded it.
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