[time-nuts] GPS Spoofing

Sat Jul 27 12:45:49 UTC 2013

About 25 years ago, I bought a bunch of LORAN-C receiver boards at the
Appelco bankrupcy auction. Despite zero doc, I got a couple running.

They had to 8085 uPs, one to compute the TDs and a second,on a daughter
board, to compute Lat/Long. The unit would repeatably hit my location w/in
a couple of hundred feet.

A trivial uP in a box could easily subtract the GPS and LORAN positions
and sound an alarm if they differed by more than a set limit, and sound an
alarm.

Furthermore, I suspect the cost to operate a set of worldwide LORAN chains
is far less than launching a single GPS bird.

-John

==================

> LORAN can be good to 60 ft.
>
>
> On 7/27/13 12:21 AM, Jim Lux 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 <jfor at 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
>>>>>
>>>>> ==============
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>> and follow the instructions there.
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>>
>>>> Chris Albertson
>>>> Redondo Beach, California
>>>>
>>>
>>>
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