81–90 of 102 posts
So a $80 million yatch can't afford an $3000 high quality gyroscope? Now you could buy amazing laser gyroscopes, for planes the Inertial navigation system error could be great, but for ships(that move more than 20X slower) is not.
[1] https://en.wikipedia.org/wiki/Attitude_control#Star_tracker
Yeah if they just used their paper charts, logged the position and compared GPS with the dead reckoning (or depth lines, radar shore returns,..) the attackers would have a much harder time... My sailing instructor always stressed that GPS is unreliable and especially when close to danger one should cross check what it says with other methods. Came in handy when my plotter failed.
The story here is that we thought we had designed a system which can do this without human interaction, and now/whenever it was discovered we're realizing we're not done yet. That this can be done by a person with a compass and a map is not a comment worth the text it's written with.
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"I believe receivers had to lock onto the civilian GPS signal before even trying to lock the encrypted military GPS." That's the old fashioned P(Y) code that they dumped because it sucked and went to the M code that doesn't need P(C) first. P(Y) code sucked because aside from needing to sync to P(C) first, they fed in the encryption stream at a varying, yet slow enough rate that you essentially got dozens of "known p…
Have you seen the "Homemade GPS Receiver" project?[1] I imagine it'd be a whole lot easier if you already have gear to receive and sample the RF side, but still an interesting challenge. Don't forget to implement CoCom restrictions :) [1] http://www.holmea.demon.co.uk/GPS/Main.htm
My favorite part of this implementation is it shows the cutting edge of modern FPGA development style, where you have soft cores and smart peripherals and the boundary is extremely fluid and blurry between them. Is that in the softcore or "discrete" logic in the FPGA? Well it depends which version of the bitstream you load into the FPGA... In the future this is how all microcontroller and video card and motherboard and such development will be done... you want a different ratio of shaders to anti-aliasing tech, or a new "hardware" supported codec, well just upload a different bitstream... May as well get used to the future of hardware development now rather than waiting.
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There is more airports in US that have GPS only approaches than airports that have ILS approaches. For example: http://155.178.201.160/d-tpp/1308/05879R25.PDF 500 ft altitude with GPS only (without vertical guidance). LPV minimum is 300 ft. Category III ILS minimum is 200 ft, Cat II -- 100 ft. But there are a lot of airports where ILS is not available.
You've got it backwards: CAT I is 200ft Decision Height (btw, not Minimum Descent) Cat II is 100ft Cat III is 0ft (with differing horizontal visibilities for IIIa/IIIb/IIIc
Yeah if they just used their paper charts, logged the position and compared GPS with the dead reckoning (or depth lines, radar shore returns,..) the attackers would have a much harder time... My sailing instructor always stressed that GPS is unreliable and especially when close to danger one should cross check what it says with other methods. Came in handy when my plotter failed.
Okay folks, "just do it manually" is not a solution. This is technology designed to make doing it manually obsolete. We're trying to design systems that can eventually run without human interaction, so saying a solution to this problem is to have a human just do it isn't viable and doesn't make sense and is fairly obvious, to boot. The story here is that we thought we had designed a system which can do this without h…
People who don't know much about GPS think the satellites are eternally autonomous but that is not the case. There are precisely two uplink control points on the planet which control them. Both in the USA as I recall.
Another interesting problem is lifetime mismatch. It would be foolish to create a system which depends on and could outlive the current GPS constellation.
Also being in the USA we tend to assume the fedgov is on our side and our side is everyone's side, but the rest of the world has found out the hard way many times over to never assume that is or will always be the case. So absolute best case is you should never deploy a worldwide system with a SPOF controlled by a foreign power.
"The story here is that we thought we had designed a system which can do this without human interaction"
No it was designed for humans (mostly US soldiers) to geolocate themselves, so they could help orient themselves on paper maps. This whole idea of pasting a navigation system, or even worse, an autonomous navigation system, on top is a good example of feature creep resulting in systemic failure.
You probably could design a redundant, tough, reliable, world wide (or at least, wide range) autonomous navigation system. It would not look anything like GPS. It would probably look a heck of a lot like a weird cross between the VOR system and authenticated LORAN. It would take a lot longer than a HN post to nail it down exactly, but I'm sure that whatever it optimized down to, it wouldn't resemble GPS very closely. In the grand tradition of all copier machines being called Xerox machines, I'm sure that whatever this successor system is called, the general unwashed masses will continue to call it a "GPS" to the immense confusion of people who actually know what they're talking about.
A planetary scale authenticated mostly decentralized web of trust mesh network of millions of stationary beacons and mobile inertial navigation systems with computational countermeasures to fight intentional bad actors? Probably providing global internet access via the mesh while you're at it, because it's there?
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I wanted to make a GPS simulator for testing my high altitude balloon's receiver to make sure it works over 15km altitude, or whatever the limit usually is. I think I gave up when I couldn't figure out how I would build the RF side. I think I got the CA PRNG code working. =) https://github.com/jevinskie/jevps/blob/master/ca.py Edit: I think I remember the issue. I started out thinking I just had to create a signal at…
So.. if you can squirt out that C/A stream from your python code at 1.023 megabits/sec all you really are asking for is a COTS BPSK modulator (minicircuits ZFAS-2000?) and a COTS L1 signal around 1.5 GHz to drive the mod. I have built N5AC microwave synth kits and I did not find it hard, but I've been doing this stuff since the 80s, so... I believe you can buy a COTS ApolLO-I board for your L1 signal. I donno if 1575…
I think my main confusion is how do I add the 4 channels together before I spit the signal out to the RF side? If they are all in phase, would it weird out the receiver because you're not going to see that in the real world? Would I have to have 4 output levels corresponding to how many channels are outputting a high level (1) during that chip/clock cycle? If them being in phase freaks out the receiver, maybe I could output the signal at 4.092 MHz and phase shift each channel by 1/4 chip/clock cycle? I was CompE so my RF/signal skills are almost zilch. =)
Good point about the cage, with the crazy low power of GPS signals, it is probably a lot easier to cause interference than with other signals.
And yes, "modulo 2 adder" is a bit verbose! =P
Perhaps interference happens a lot more often that we think.
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Humans, like water, take the easiest route. Unless someone is particularly vigilant and routinely checks the gyroscope to verify the course the GPS is using you wouldn't notice the "hijack" till it was too late. Most people I know wouldn't be paranoid enough to verify their own course against a gyroscope, or any other means of determining coordinates.
That "someone" could simply be the computer.
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Okay folks, "just do it manually" is not a solution. This is technology designed to make doing it manually obsolete. We're trying to design systems that can eventually run without human interaction, so saying a solution to this problem is to have a human just do it isn't viable and doesn't make sense and is fairly obvious, to boot. The story here is that we thought we had designed a system which can do this without h…
Thats a terrible system design, because all single points of failure eventually fail. Curl up and die is not a valid response to failure. The only valid solution always must end with "do it manually", that can never be removed. Doesn't matter if its a plane, ship, refinery/chem plant, or reactor control rod. People who don't know much about GPS think the satellites are eternally autonomous but that is not the case. T…
And GPS isn't what I was talking about, the automatic navigation system on the $80 million yacht was the system we designed which we thought could be run without human interaction.
And your paranoid delusion that the US can/would use its GPS satellites offensively is just that - paranoid delusion.