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Old 05-08-2013, 23:35   #106
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Re: Dust Off Your Sextants! GPS Hacked!

"No. You just need a gps receiver that receives their signal "
Not quite. You need a gps that can use their military signal after they've switched off their civilian one. All four GPS systems (US, Glosnass, Compass, Galileo) have the ability to shut down or degrade the civilian signal that they allow the public to use, while still providing their military signal.
So any of the systems can shut you out, unless you've got access to the military receivers.
And of course, if the normal accuracy is enhanced by something equal to the WAAS augmentation in the US, you also have to be "local" enough to use that.
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Old 06-08-2013, 07:52   #107
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Re: Dust Off Your Sextants! GPS Hacked!

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Can they keep me from using their GPS?
Since reports are that there system is encrypted, I would say yes, they can keep you from using it.
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Old 06-08-2013, 08:40   #108
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Re: Dust Off Your Sextants! GPS Hacked!

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(the TSA has probably killed more people then died in 9/11).
I believe that the TSA has certainly has cost this country more than the fall of the trade center, but I am not familiar with them having killed a whole lot of people. Could you possibly give a few references on that?
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Old 06-08-2013, 08:51   #109
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Re: Dust Off Your Sextants! GPS Hacked!

It has been suggested by a certain element of the US political system that the actions of the TSA is causing more people to travel by automobile resulting in 1200 more unnecessary deaths by automobile yearly.

TSA wastes $1.2 billion a year and causes 1,200 unnecessary deaths annually | Human Events
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Old 06-08-2013, 09:07   #110
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Re: Dust Off Your Sextants! GPS Hacked!

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It has been suggested by a certain element of the US political system that the actions of the TSA is causing more people to travel by automobile resulting in 1200 more unnecessary deaths by automobile yearly.

TSA wastes $1.2 billion a year and causes 1,200 unnecessary deaths annually | Human Events
They certainly have me driving more and flying less, so from that perspective, I would not be surprised that overall, more people have been killed by deciding to drive, rather than fly and deal with the hassles.

I think forever more, TSA will remain the quintessential example of just how bad a job the government can do, when it really tries. Nothing but expensive (and annoying) window dressing.
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Old 07-08-2013, 23:44   #111
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Re: Dust Off Your Sextants! GPS Hacked!

One underreported aspect of those "GPS Spoofing" experiments is that the same groups that are trying to spoof the GPS system are also investigating ways to detect spoofing. And they have come up with quite a few ways.
There are two counter measures available that are already within budget for serious cruisers.
This is a GPS compass made by Hemisphere, and rebranded and sold by many marine electronics manufacturers. It appears to retail for about $2000.-
This device can measure the angle the incoming GPS signals come from. (This is how it determines it's orientation after all). It has also a complete inertial navigation system on board. So it could detect spoofing by:
- Comparing the angle a GPS signal comes from with the angle it ought to come from (or just comparing it's heading output with a gyro or conventional compass)
- Comparing inertial and navigation GPS results.

I say "could", because I don't know if it would. It has the hardware on board, but I don't know if it has the needed software. I am however quite certain that if GPS spoofing really becomes a problem, that the manufacturers of GPS devices like Hemisphere will react by enabling anti spoofing functions. Would probably just be a firmware update...
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Old 08-08-2013, 00:09   #112
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Re: Dust Off Your Sextants! GPS Hacked!

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There are two counter measures available that are already within budget for serious cruisers. . . . It appears to retail for about $2000.
For some people, $2k might be within budget for a GPS, not for this cruiser. When I get all fitted out I want to spend about $3k total on all navigational electronics.

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This device can measure the angle the incoming GPS signals come from. (This is how it determines it's orientation after all). It has also a complete inertial navigation system on board. So it could detect spoofing by:
While the advertisement talks about comparing the phase difference between the two associated antennaes, it is not clear that it is using that info to determine direction of signal. It may just be a means of improving performance thru some mathematical means, it may be a way to correct for pitch and roll errors. To detect signal direction, my understanding is that you would need several antennae (4+), and to achieve the kind of accuracy they are claiming would require many antennae (20+). All single antennae GPS compare the location from 1s ago (or some specified time) with current position to determine heading. I don't see this rig departing from that protocol for basic operation.

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(or just comparing it's heading output with a gyro or conventional compass)
This would work as long as actually heading and GPS heading didn't coincide. The spoofing signal may have you on the same heading but in the wrong location.
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Old 08-08-2013, 00:41   #113
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Re: Dust Off Your Sextants! GPS Hacked!

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All single antennae GPS compare the location from 1s ago (or some specified time) with current position to determine heading. I don't see this rig departing from that protocol for basic operation.
.
GPS compasses are expensive but they are used in some up market yachts. They provide a better stabilised heading than a gyro compass, or flux gate compass, which is the cheaper option fitted to most yachts.

This enables a more accurate autopilot and MARPA (or ARPA) performance.
They function as a true direction indicator unlike normal GPS units ( that will only indicate COG (in other words the direction you are traveling not pointing) unless they also have a fluxgate compass.

GPS compasses are the ultimate compass for a yacht (providing you have a reliable electricity supply)

Presumably a GPS compass could be spoofed like the GPS position signal. A conventional, flux gate or gyrostabilised compass can also be spoofed, but it requires different technology to spoofing the GPS signal. However the risk of spoofing a private yacht is more fantasy than reality.
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Old 08-08-2013, 03:02   #114
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Re: Dust Off Your Sextants! GPS Hacked!

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For some people, $2k might be within budget for a GPS, not for this cruiser. When I get all fitted out I want to spend about $3k total on all navigational electronics.
It's certainly within budget for the kind of ship that was the target of the spoofing experiment this thread started with. I would consider it too. And I would expect the price to go down.


Quote:
While the advertisement talks about comparing the phase difference between the two associated antennaes, it is not clear that it is using that info to determine direction of signal. It may just be a means of improving performance thru some mathematical means, it may be a way to correct for pitch and roll errors. To detect signal direction, my understanding is that you would need several antennae (4+), and to achieve the kind of accuracy they are claiming would require many antennae (20+). All single antennae GPS compare the location from 1s ago (or some specified time) with current position to determine heading. I don't see this rig departing from that protocol for basic operation.
This device measures bearing, not course, and to do that it does indeed have two antennas, 50 cm apart, and use phase differential measurements to determine direction.
I must say I am surprised by how far GPS has come since my days as a geodesy student.

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This would work as long as actually heading and GPS heading didn't coincide. The spoofing signal may have you on the same heading but in the wrong location.
No, because if the device can measure the direction signals come from the spoofing would only work if the spoofer locates itself at exactly the right bearing from the target. That would be quite a challenge.
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Old 08-08-2013, 03:06   #115
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Re: Dust Off Your Sextants! GPS Hacked!

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Presumably a GPS compass could be spoofed like the GPS position signal.
I suppose it would be quite a challenge, since you would have to spoof all visible GPS satellites, and do it with transmitters located at the right bearing. So 8+ transmitters, moving around the target... I doubt it would be feasible.
Gyros of course can be spoofed too. All you need is a sufficiently dense material, say depleted uranium, in a reasonably large quantity, say a few cubic miles...
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Old 08-08-2013, 09:27   #116
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Re: Dust Off Your Sextants! GPS Hacked!

Within the marine industry it is common practice to identify something to fear and then invent a solution.

This is one of those.
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Old 08-08-2013, 10:21   #117
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Re: Dust Off Your Sextants! GPS Hacked!

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Within the marine industry it is common practice to identify something to fear and then invent a solution.

This is one of those.
.........to sell
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Old 08-08-2013, 11:32   #118
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Re: Dust Off Your Sextants! GPS Hacked!

We are already working on the expensive upgrade that will be required for your boat to fix this err...problem and keep you safe and happily sailing in the sun with drink in hand.
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Old 08-08-2013, 12:58   #119
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Re: Dust Off Your Sextants! GPS Hacked!

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Indeed. My sextants have never actually collected dust, and when I went to a new (to me) harbour last weekend, my wife bought us the paper chart.

I used the paper chart to determine bearings (I use a handheld pelorus), to familiarize myself with the anchorage areas, should that have become desirable or necessary, and to check chart datum depths. My sounder confirmed that we currently have lake levels up a fair bit. I used the GPS to figure out ETAs and offsets from waypoints like known buoys. As it was a bright, clear day and I could identify landmarks easily, I did not bother with the sextant. Fogged in shore, at night, or on a barren stretch, I do occasionally use it.

GPS is great...a huge help. But I do not consider it definitive or the only method of locating oneself. Aside from the obvious need GPS receivers have for batteries or ship's power, there have been irregularities over the years, such as "5 knots....5.1 kn....67.2 kn....4.9 kn...." as one of the four or five satellites acquired has a reset or a thruster burp or is nudged by a coronal discharge. GPS doesn't often go wrong, but a subtle error could in fact go unnoticed unless the skipper is using at the same time other methods of pilotage.

APs are best set on bearings provided by fluxgate compasses, or even from chart-acquired paperwork. Deviations from course are revealed pretty quickly and valuable inputs about making lee, drift and current set are seen. The idea of GPS being hacked in order to skew a ship's AP to either drive it ashore or toward pirates (as an example) is a nightmare prospect akin to hacking a pacemaker and gradually increasing someone's heart rate.

Use GPS as only one input of many, however, and a "hacked" GPS is revealed before trouble can take root.
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And that statement boys and girls is what pilotage is all about. The rest is details.
Correcomundo.

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