When Cape Cod LORAN was functional, I could easily see the pulses with a few turn coil maybe a foot in diameter, roughly resonated, and a scope.
-John ====== > 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 >>>>>>> >>>>>>> ============== >>>>>>> >>>>>>> >>>>>>> >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- time-nuts@febo.com >>>>>>> To unsubscribe, go to >>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>> and follow the instructions there. >>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> >>>>>> Chris Albertson >>>>>> Redondo Beach, California >>>>> >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- time-nuts@febo.com >>>>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
