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 <mkperr...@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 <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
>>>>>> 
>>>>>> ==============
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> _______________________________________________
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>>>>> 
>>>>> 
>>>>> 
>>>>> --
>>>>> 
>>>>> Chris Albertson
>>>>> Redondo Beach, California
>>>> 
>>>> 
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