[time-nuts] GPS Spoofing
Scott McGrath
scmcgrath at gmail.com
Sat Jul 27 17:35:10 UTC 2013
Key
Problem with GPS is its easy to spoof on one level and have a complete denial of service on the other. Out in California a while back a malfunctioning TV distribution amplifier jammed a major harbor and surrounding almost 25 sq miles affected all because of a 49.95 TV amp had a problem. The military receivers had the same problem
LORAN is virtually jam proof unless you have a very powerful transmitter
Sent from my iPhone
On Jul 27, 2013, at 11:17 AM, Michael Perrett <mkperrett at gmail.com> wrote:
> 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 <scmcgrath at 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 <jimlux at 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 <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
>>>>>>
>>>>>> ==============
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> time-nuts mailing list -- time-nuts at febo.com
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>>>>>
>>>>>
>>>>>
>>>>> --
>>>>>
>>>>> Chris Albertson
>>>>> Redondo Beach, California
>>>>
>>>>
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