I have seen a lot of differing opinions on GPS Spoofing and using back up
systems on this thread. Most pretty good, but a couple off the mark a bit.
Here are a couple of comments on GPS Spoofing.
- There are anti-spoofing GPS receivers available - to "authorized"
users. Typically DOD. Most, if not all, military receivers utilize the
encrypted "P-Code", while civilians must use the more vulnerable clear text
"C/A code". The P-Code signals are very difficult to spoof unless you have
a-pirori knowledge. The newer satellites (GPS III) will have an even more
robust AS methodology.
- Note: beware of P-Code, or Military, receivers available on eBay.
They are useless without the encryption keys distributed by the US
Government.
- In the (near?) future there will be four civilian GPS Signals: "The
government is in the process of fielding three new signals designed for
civilian use: L2C, L5, and L1C. The legacy civil signal, called L1 C/A or
C/A at L1, will continue broadcasting in the future, for a total of four
civil GPS signals. Users must upgrade their equipment to benefit from the
new signals". ref
http://www.gps.gov/systems/gps/modernization/civilsignals/
- Receivers utilizing the new civilian GPS frequencies can solve the GPS
equations from more than one frequency and see if any one signal is being
spoofed. The new civilian frequencies will be more spoof resistant.
Comments on using inertial measurement units (IMUs) to back up GPS.
- Current IMUs with even a "good" drift rate of say, 1 degree per hour,
available for around a few thousand dollars, will be off 60 nautical miles
after an hour of uncorrected operation. That can be reduced by other sensor
inputs (GPS, LORAN, pit-log or what ever you have), but the navigation
solution will eventually degrade to the accuracy of the external sensor. If
my memory serves me for a really deep pocket navigator (having tens to
hundreds of thousands of dollars, and a large amount of available mounting
space) IMUs with drift rates of up to a thousand times less can be
purchased (that's ,001 miles per hour, or around a couple of meters per
hour), think submarines, etc.
Using a dual sensor navigation system (or timing system! ), such as
GPS/eLORAN, would obviously make the system so much more robust.
Michael / K7HIL
On Sat, Jul 27, 2013 at 6:43 AM, Scott McGrath <scmcgr...@gmail.com> wrote:
> Key here is how does the captain know that GPS is no longer providing an
> accurate fix? You need 2 or more independent systems to cross check each
> other.
>
> Sent from my iPhone
>
> On Jul 27, 2013, at 12:21 AM, Jim Lux <jim...@earthlink.net> wrote:
>
> > On 7/26/13 8:45 PM, J. Forster wrote:
> >> I gather from the article, the GPS position was spoofed and the
> autopilot,
> >> in bringing it back to where it was supposed to be, actually took it off
> >> course.
> >>
> >> There are places where a few hundred feet makes a big difference, viz.
> the
> >> Costa Concordia.
> >>
> >> IMO, this is a very convincing reason for something like LORAN.
> >
> > I think it's a convincing argument for a captain who pays attention to
> the other navigation instruments and doesn't blindly follow the GPS.
> >
> > It's also a convincing argument that shipboard
> automation/autopilot/autocontrol vendors need to make more sophisticated
> software (which I suspect they do, particularly on 200+ foot ships.. I
> would imagine that there are some aspects of this demo that are contrived.)
> The ship making and driving business is pretty unregulated. It's all about
> what the owner of the ship is willing to pay (or what he needs to get
> liability insurance, if he wants). There's nothing even remotely like
> DO-178 for shipboard stuff.
> >
> > The folks doing stabilized oil rigs probably have sophisticated systems,
> but they're also using IMUs and other stuff. Ditto for high value things
> (oil tankers, warships). Molasses tankers? They're probably lucky to have
> a functioning compass and some old charts.
> >
> >
> > I'm not sure, though, that looking at the big picture, whether your tax
> dollars are better spent on LORAN, or on some other precision navigation
> method or on making jam resistant GPS receivers (which do, in fact exist,
> and make use of things like direction of arrival of the signal..)
> >
> > Note that a GPS system with 3 antennas (as is common in systems that use
> GPS to derive attitude/orientation) would be extremely difficult to spoof,
> and would be VERY inexpensive to implement. Either the carrier phases and
> code phases are consistent for all the received signals or they're not. A
> jamming signal coming from the wrong direction will not have the right
> direction of arrival relative to the platform orientation. One wrong
> signal might be tolerable (multipath, etc.) but with a multi satellite fix,
> I suspect it would be hard to do it.
> >
> > Sure, one could throw up N pseudolites on a bunch of UAVs, etc., but
> that's getting to be a bit noticeable.
> >
> >
> > For what it's worth, I don't know that LORAN has the performance to
> avoid a Costa Concordia type foul up (assuming they were crazy enough to do
> the near pass in the fog, so visual navigation didn't work)
> >
> > I seem to recall that LORAN had 1/4 nmi kinds of accuracy. it would get
> you to the channel or mouth of the harbor, but not get you into your berth.
> You might be familiar with the local propagation anomalies and get better
> accuracy with experience in your local waters.
> >
> >
> >
> >
> >
> >
> >>
> >> -John
> >>
> >> =================
> >>
> >>
> >>
> >>> I boat? The backup is a competent captain. He'd see the compass
> heading
> >>> move and quickly disengage the autopilot. I had a boat for years I'd
> >>> notice a 5 degree change. Mine was a sailboat so I'd be more
> sensitive to
> >>> heading changes than a power boater but still the human is the backup.
> >>>
> >>> Most autopilots don't directly follow GPS, they use GPS to determine a
> >>> heading, follow it then use GPS to detect drift and re-compute the
> >>> heading.
> >>> the heading would be held by a compass sensor in a low-cost setup or
> in a
> >>> larger setup a lazer ring gyro backed up by a compass. So a spoofed
> >>> GPS
> >>> would cause the autopilot to "think" there was a bigger crooswnd or
> >>> current
> >>> and make a bigger heading change.
> >>>
> >>> I bet you could hijack a drone not a manned vehicle the pilot is
> trained
> >>> to
> >>> monitor the automation and he'd very quickly turn it off thinking it
> was
> >>> broken.
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>> On Fri, Jul 26, 2013 at 8:41 AM, J. Forster <j...@quikus.com> wrote:
> >>>
> >>>> Prof. Humphry from Texas just reported being able to spoof GPS in the
> >>>> Med
> >>>> and take over the nav system of a luxury yacht. He's done this before
> >>>> with
> >>>> a drone in the US.
> >>>>
> >>>> LORAN as a backup, at least?
> >>>>
> >>>> -John
> >>>>
> >>>> ==============
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> time-nuts mailing list -- time-nuts@febo.com
> >>>> To unsubscribe, go to
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> >>>> and follow the instructions there.
> >>>
> >>>
> >>>
> >>> --
> >>>
> >>> Chris Albertson
> >>> Redondo Beach, California
> >>
> >>
> >> _______________________________________________
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