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Bypassing US GPS Limits For Active Guided Rockets 126

Posted by timothy
from the use-for-good-not-for-evil dept.
Kristian von Bengtson writes with a link to a short guest post at Wired with an explanation of how his amateur rocket organization Copenhagen Suborbitals managed to obtain GPS receivers without U.S. military limits for getting accurate GPS information at altitude. Mostly, the answer is in recent relaxations of the rules themselves, but it was apparently still challenging to obtain non-limited GPS hardware. "I expect they only got the OK to create this software modification for us," von Bengston writes, "since we are clearly a peaceful organization with not sinister objectives – and also in a very limited number of units. Basically removing the limits is a matter of getting into the hardware changing the code or get the manufacturers to do it. Needless to say, diplomacy and trust is the key to unlock this."
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Bypassing US GPS Limits For Active Guided Rockets

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  • by Anonymous Coward

    Honestly I am a little surprised no one on Alibaba sells unlocked gps. There are enough tech manufacturers outside the US that you think someone would sell it.

    • Cruise missiles go a long way in expressing customer dissatisfaction, I guess.

    • Re:Huh (Score:5, Interesting)

      by interkin3tic (1469267) on Tuesday October 01, 2013 @10:25AM (#45002395)
      Demand is pretty low I guess. When I was playing ingress and my GPS signal was bouncing away from what I was trying to capture, I sometimes feverishly thought "I'm going to look up how to get MILITARY GRADE GPS on my phone! Then I'll be unstoppable!" But even if someone offered a phone with that, and even if it did improve ingress, and even if I did still play, I'd only be willing to pay an extra $30 for it. That's the only use I'd have for unlocked GPS, and I don't even currently have it. Non-nerds don't even realize the GPS we civilians use is limited.

      For that matter, I was talking to a friend who is in the marines and who... er... does stuff with maps for driving humvees. She didn't know if she used the military GPS, she didn't even know her iphone GPS was limited.

      What seems strange to me is that they do limit GPS in the first place. Seems like anything where military level GPS could be used dangerously, it's not that high of a barrier. You don't need super accurate GPS to make a car bomb, and if you're competent to make your own attack drone, you probably know how to bypass the restrictions.

      (Hi, NSA. Congrats on keeping your jobs when government workers who DON'T shit on the constitution aren't being paid.)
      • Re: Huh (Score:5, Informative)

        by mpoulton (689851) on Tuesday October 01, 2013 @10:45AM (#45002683)
        The limitations at issue are not accuracy limits. Nowadays there are no real differences in accuracy between military and civilian GPS, since selective availability was turned off years ago. The problem is that civilian GPS firmware prohibits the device from giving a fix if it is above a certain altitude (around 60,000 feet) and moving faster that about mach 1. This makes it useless for midcourse guidance of a rocket, which is the point.
        • by Anonymous Coward

          "The problem is that civilian GPS firmware prohibits the device from giving a fix if it is above a certain altitude (around 60,000 feet) and moving faster that about mach 1. This makes it useless for midcourse guidance of a rocket, which is the point."

          I see. So a V1 would be Ok to use, good to know.

        • Re: Huh (Score:5, Informative)

          by Andy Dodd (701) <atd7@co[ ]ll.edu ['rne' in gap]> on Tuesday October 01, 2013 @11:08AM (#45002955) Homepage

          Not entirely true. The P/Y code still offers improved accuracy compared to even a non-degraded C/A code due to it being transmitted at 10x the rate of the C/A code. It also allows for dual-frequency operation, permitting ionospheric delay to be corrected for. (There are tricks to using the P/Y code to obtain iono delay even without the decryption keys by cross-correlating the signals on each frequency, but these require a LOT of data collection and processing and I think the receiver has to be stationary.)

          That said, modern civilian receivers do such a good job of processing the C/A code that they come close to matching many military receivers which are processing the P/Y code with far older hardware/software algorithms. Systems like WAAS can compensate for a large amount of ionospheric delay even without dual-frequency operation.

          Upcoming GPS satellites will permit civilian dual-frequency operation.

          • Re: Huh (Score:5, Informative)

            by Bob the Super Hamste (1152367) on Tuesday October 01, 2013 @12:46PM (#45004167) Homepage
            Check out RTK [wikipedia.org] systems using the L2 carrier to figure out the ionospheric error. Yes you do need a stationary unit and also a mobile unit. If you want real time corrections you need a wireless link between them to transmit the corrections over and it becomes harder to get rid of the off by 1 error that is often prevalent. More popular is to have a base station that is operational recording raw pseudo range and carrier phase data at a well known position (survey bench mark or from a long initial self survey) and a roving unit also collecting the pseudo range and carrier phase data. Once your surveying is done the data is post processed to provide highly accurate results. The problems with single reverence station RTK solutions like that is that you are limited to a radius of about 10mi (might be km) before the accuracy starts falling off so a better solution is having a CORS network [state.mn.us] with the ability to create virtual reference stations from "near by" reference stations.
        • Re: Huh (Score:4, Insightful)

          by interkin3tic (1469267) on Tuesday October 01, 2013 @11:17AM (#45003075)
          Ah, so I'm basically wrong. I'm trying to make a joke about inaccurate GPS and making uninformed posts to slashdot, but I've got nothing. So I'm just going to say "Good to know, thank you!"
        • by BitterOak (537666)

          The problem is that civilian GPS firmware prohibits the device from giving a fix if it is above a certain altitude (around 60,000 feet) and moving faster that about mach 1. This makes it useless for midcourse guidance of a rocket, which is the point.

          Is someone with the technical abilities to build a guided missile really going to be deterred by the fact that off the shelf civilian GPS firmware is crippled in this way? The specifications for the GPS system are publicly available and many manufacturers have successfully used them to build GPS receivers, so it can't be rocket science (pun intended). And even if one were to use off the shelf GPS components, how hard would it be to modify the firmware? Firmware is just software stored in some type of rea

          • It's more likely that there are some sort of cryto-keys required to access the other signal bases. Without those keys, you're SOL, even if you could reverse engineer the software.

            • The keys would have to be stored in the firmware somewhere, just a matter of finding and recognising them.

              • by sirsnork (530512)

                Yes, they would be stored in the firmware somewhere.... on a military grade receiver only. If you have that then it becomes kind of a moot point if you can hack the firmware of a standard unit.

                The keys would not be in the normal units because they don't need to be

          • Re: Huh (Score:5, Informative)

            by mpoulton (689851) on Tuesday October 01, 2013 @12:12PM (#45003769)

            Is someone with the technical abilities to build a guided missile really going to be deterred by the fact that off the shelf civilian GPS firmware is crippled in this way? The specifications for the GPS system are publicly available and many manufacturers have successfully used them to build GPS receivers, so it can't be rocket science (pun intended). And even if one were to use off the shelf GPS components, how hard would it be to modify the firmware? Firmware is just software stored in some type of read only or flash memory. Would it be that hard to download, inspect and modify it? It seems to me it would be about as hard as removing copy protection from a game.

            Yes, it is a substantial deterrent. The limitations are imposed in the lowest-level parts of the GPS receiver, the first stage of data processing at which it is technically feasible to infer speed and altitude. The hardware that runs this code is highly specialized - it's a mixed analog/digital RF ASIC that is designed in hardware to run that specific code, including the limitation. There is little distinction between hardware and firmware at that point, and it is likely that the code responsible for the limitation is not programmable/reprogrammable at all. The sophistication needed to build a rudimentary short-range guided missile is surprisingly basic, and many hobbyists (or terroristically-inclined groups) could do it without too much difficulty, on a five-figure or low-six-figure budget. The GPS limitation significantly hinders the on-target accuracy that could be achieved, since the high speed terminal phase of the flight is where excellent guidance in an absolute reference frame is most important. The sophistication needed to build or microscopically alter a GPS receiver without the limitation is significantly greater (and in an entirely different technical field) than what is needed to build a missile that would benefit from that GPS guidance.

            • Ever looked how many DIY GPS receivers are out there? On a six figure budget it wouldn't be much trouble getting something made.

              • Re: Huh (Score:4, Insightful)

                by slew (2918) on Tuesday October 01, 2013 @03:08PM (#45005849)

                Ever looked how many DIY GPS receivers are out there? On a six figure budget it wouldn't be much trouble getting something made.

                Although there are many so-called DIY GPU receivers out there, all of them I know about use off the shelf GPS modules (like the MTK3339 or perhaps some of the SiRF stuff), not doing the RF stuff themselves. There are some people making the RF stuff as DIY projects, but then they have to stuff the signal into an FPGA and drive the thing with a lump of software.

                Having tried the later myself, I can tell you it's generally a bit finicky even in the simple case. I suppose if you know what you are doing you might have better luck (because of w/o a lot of experience, ionospheric noise modelling isn't very easy, it's much easier to just average stuff and hope for the best). Another roadblock is that most folks I know don't have many 60K/Mach velocity platforms to test on to perfect their dopper shift algorithms (remember, the satellites are moving too and you have to account for that)...

                I don't think you are just going to download some DIY GPS receiver in the webosphere and have to work for missle guidance applications.

                • There's another comment in the thread with a link to a guy who has done all that for a hobby.

                  I also personally know another small team (2 people) who did it as part of a rocketry hobby and now sell the receivers commercially that they designed.

                  It is hard, but not impossible. It's within the capability of a single, very smart, very motivated individual.

                  • by cusco (717999)

                    Most things are. Fortunately most very smart, very motivated individuals tend not to be amoral sociopaths. That's probably the reason why we haven't been overrun by manufactured plagues and the electrical grid doesn't crash every week.

        • by X0563511 (793323)

          Accuracy isn't even the Big Deal with it, it's authentication.

        • There still are differences in the accuracy between military and civilian gps but it isn't the 10s of meters that was in place with selective availability. The military gps has access to the unlocked L2 channel while the civilian one still just has access to the L1 data. By having both the L1 and unencrypted L2 data it is possible to do RTK like corrections within a single device instead of having 2 devices with one at a well known location sending corrections to a mobile one. For most people a +-3 meter ac
        • Considering most are OK with GPS-assist in their phones this is pretty much a non-issue. It affects such a small subset of people that who really cares. Model rocketry hobbyists I guess which is kind of geeky which is why I suppose it is even listed here at all. Even among that subset, there is only going to be an even fewer number that would exceed that ceiling for GPS operation.

          I mean when I got into GIS the turned off the GPS limitations for civilians, THAT was a big news story. You no longer really had

      • by Kjella (173770)

        What seems strange to me is that they do limit GPS in the first place. Seems like anything where military level GPS could be used dangerously, it's not that high of a barrier. You don't need super accurate GPS to make a car bomb, and if you're competent to make your own attack drone, you probably know how to bypass the restrictions.

        Well we're mixing apples and oranges here, there is a civilian signal and a military signal and what this article is talking about is removing some software limitations on where and when a civilian GPS unit will work, in short if you tried to use one aboard an airplane it'd blank out, not because it couldn't get signal but because the reciever is too high and going too fast for what is permitted. They still can't decrypt the military signal which gives them higher accuracy and timing signals to make precisi

        • Do you really need precision strikes for high speed missiles?

          I found my wife's phone that she dropped in a park by using Find Your iPhone app.

          That's probably close enough for any missile.

          • But it's not accurate enough for sharks with lasers heads.

          • Do you really need precision strikes for high speed missiles?

            Civilian GPS is not "low precision" at high altitude/speed, it stops working completely. If you are above 60,000 feet OR going faster than 999 knots, then it is supposed to completely shutdown.

            • by X0563511 (793323)

              If you can keep the GPS online until 60,000 and then turn it back on when you drop below, that's probably enough for the job. On the way up it establishes your ballistic arc, and on the way down you can correct for peterbances that occurred. Basic INS stuff could deal with the between.

            • Actually it is suppose to be an AND not an OR but most manufactures of civilian stuff find it is easier to do an OR since how often do regular people travel above 60,000 feet or travel above 1000 knots. In the hobbyist market for GPS modules it is a selling point that they operate with the AND instead of the OR functionality.
          • Depends on the traget and what your shooting at it, trying to detonate a 50 Kt MIRV within 300 m of a reinforced missile silo at 12,000MPH is pretty tough, an 81mm mortar round within 35 m of a crowd in a park is pretty easy.

            • How is the GPS accuracy any different for either?

              You're talking about flight characteristics.

        • by X0563511 (793323)

          Not very many passenger flights extend beyond 60,000' and/or 1000 knots...

      • What seems strange to me is that they do limit GPS in the first place.

        So that they can charge 10 or more times more for GPS receivers sold to the military.

      • Re:Huh (Score:5, Interesting)

        by Sarten-X (1102295) on Tuesday October 01, 2013 @11:04AM (#45002907) Homepage

        if you're competent to make your own attack drone, you probably know how to bypass the restrictions.

        Well, yes... but it's one more thing to screw up, and it takes time, and you need someone who knows how to reprogram a receiver's firmware rather than just an Arduino, RPi, or other DIY autopilot.

        Amazingly, the US government does actually understand that perfect security is impossible. Rather, the modern security strategy is centered around making enemy attacks more difficult, ideally requiring so much planning and expertise that they can be noticed and stopped before coming to fruition. As you've seen, most folks don't know that GPS is artificially limited, and most normal applications don't need the high precision of an unlimited receiver. When someone starts asking around on forums or posting classified ads looking for GPS firmware experts, suspicions are rightfully raised.

        Of course, with more suspicion comes the need to eliminate such suspicion. If you're claiming to need unrestricted GPS for rocketry, this probably isn't your first rocket. There's likely records of supply purchases, perhaps travel to launch sites, and probably even phone records of you calling other rocketry experts. If only there was some big searchable database of exculpatory evidence, to help quickly separate the valid suspicions from the false positives...

        NSA... shit on the constitution...

        What seems strange to me is that we're mad at the NSA for invading our privacy, when we really should be mad at them for having poor access control. In my opinion, the NSA's databases should be kept operational, but with a PR campaign and better operational security. Database queries must be associated with an ongoing investigation, which could be started with as little as an anonymous tip, and must end either with escalation (to the judicial branch) or dismissal accompanied by a letter to the target disclosing the inquiry and its nature. Records should also be subject to subpoenas, but their contents must be reviewed by the judge prior to inclusion in any trial.

        The NSA has built the ability to find evidence on an unprecedented scale. We should not fear such an ability, but rather we should be demanding that such power directly and visibly serves the people.

        • Re:Huh (Score:5, Interesting)

          by TheCarp (96830) <sjc&carpanet,net> on Tuesday October 01, 2013 @11:50AM (#45003517) Homepage

          > The NSA has built the ability to find evidence on an unprecedented scale. We should not fear such
          > an ability, but rather we should be demanding that such power directly and visibly serves the people.

          I am not really sure I agree. A lot of progress socially and morally has come from law breakers. What goes on behind closed doors is a rather new area to be moving into and reveals many things that we may or may not have known was going on before...and I am not so sure thats unmitigated good.

          If these abilities existed 30 years ago, where would the gay rights movement be today? Making it easier to gain "evidence" could have been absolutely terrible then. Had they existed 50 years ago, would the civil rights movement been able to organize?

          What makes us think that today we have it all right and from this point forward knowing about everything will just be good? Frankly, I doubt a society that can enforce all of its laws all the time is capable of progress.

          • by Sarten-X (1102295)

            A lot of progress socially and morally has come from law breakers.

            As has a lot of regression and resistance to change.

            When an activist intentionally breaks a law as an act of civil disobedience, usually the goal is to be caught. During the ensuing trial, the activist's chosen issue is discussed in the media at length. Privacy surrounding the act is undesirable, and the records of the activist's actions leading up to the event would be subject to the judge's review before being made public. As a matter of course, anyone accused of a crime could be protected from inquiries

            • by TheCarp (96830)

              > When an activist intentionally breaks a law as an act of civil disobedience,
              > usually the goal is to be caught

              So was every gay person who engaged in relationships with other gay people an activist? Or were they all criminal scum because they didn't intend to get caught?

              > As a matter of course, anyone accused of a crime could be protected from inquiries
              > without a warrant, to prevent overzealous prosecutors from going after the activist's associates.

              As a matter of course, we already can see the

              • by Sarten-X (1102295)

                So was every gay person who engaged in relationships with other gay people an activist? Or were they all criminal scum because they didn't intend to get caught?

                In accordance with due process, anyone "getting caught" through a well-regulated surveillance system would first have been caught through normal means. This is why I specified that any information coming out of queries should simply be handed over to the judicial branch. Even with clear evidence, it's still the prosecutor's job to make a case, and there is always the possibility of legitimate jury nullification. Prosecutors are not required to prosecute every crime, whether or not anyone was harmed.

                Anyone e

                • by khallow (566160)

                  In accordance with due process, anyone "getting caught" through a well-regulated surveillance system would first have been caught through normal means.

                  I see the source of your confusion. Like just about everyone else, law enforcement or whatever would instead use the easiest way. They'd filter through the NSA data for the desired information, then manufacture a legitimate seeming way to get that information (say, via an "anonymous phone call" from a confederate) to hide how they illegally got the data.

                  And that's assuming erroneously that they are trying to follow the forms of legal law enforcement. Instead, they might use the information to create a pr

                • by TheCarp (96830)

                  >Personally, I'm inclined to agree that free expression is one of those "blessings of liberty",
                  > but I prefer having functional authority.

                  See and I come to this and see this is where we clearly most disagree.... because I firmly believe that without the blessings of liberty "functional authority" is an oxymoron. Without those there can be no legitimate authority.... just a large bunch of thugs.

        • by khallow (566160)

          The NSA has built the ability to find evidence on an unprecedented scale. We should not fear such an ability, but rather we should be demanding that such power directly and visibly serves the people.

          What's the point of this "demand"? This power is easy to abuse and there's no such means to put in safeguards and accountability - aside from removing the power in the first place.

      • What seems strange to me is that they do limit GPS in the first place. Seems like anything where military level GPS could be used dangerously, it's not that high of a barrier. You don't need super accurate GPS to make a car bomb, and if you're competent to make your own attack drone, you probably know how to bypass the restrictions.

        It is just an export limit. We can have/use the technology here in the US as long as it stays here. Relevant ITAR restrictions are:

        "Designed for encryption or decryption (e.g., Y-Code) of GPS precise positioning service (PPS) signals;"

        "Designed for producing navigation results above 60,000 feet altitude and at 1,000 knots velocity or greater;"

        There is not really a "soft" restriction on accuracy because none of us possess the decryption key for military carrier. Limits on accuracy is mostly caused

        • by tlhIngan (30335)

          There is not really a "soft" restriction on accuracy because none of us possess the decryption key for military carrier. Limits on accuracy is mostly caused by "ionospheric delay" from signals traveling thru charged upper atmosphere. Now that other GPS constellations are in operation it is possible to construct a receiver to concurrently examine timing/phase of multiple carrier frequencies to get an active handle on ionospheric delay and significantly improve accuracy. New civilian signals being added to GP

        • You don't even need other GPS like constellations to do the necessary corrections. Differential GPS has been around for years as a simple solution and for more accuracy RTK solutions have been developed that operate with the US GPS. The biggest benefit of having multiple GPS like constellations is that you don't need your own reference station and can do it all in one device. Or you could do what the EU's Galileo system does and basically have 2 open channels providing data (the US GPS also has 2 channels b
      • by dgatwood (11270)

        Demand is pretty low I guess.

        If so, it means that the hardware manufacturers are too clueless to recognize that it's a serious problem. I have GPS in my Canon 6D and nearly returned the camera because I thought the GPS had died after a week. Why? Because I had gotten on an airplane, which caused GPS to shut off internally, and it never came back on. After yanking the battery, it started working, at which point I thought for a moment, remembered that ridiculous restriction, and realized what had happened

        • Why? Because I had gotten on an airplane, which caused GPS to shut off internally

          Others here are saying that the required limits are 60,000 ft and 999 knots.

          Did you take a particularly fun plane ride?

          • by dgatwood (11270)

            Interesting. I'm wondering if Canon's hardware uses a much lower limit, as I've seen this behavior on multiple plane rides, and nowhere else.

            • Interesting. I'm wondering if Canon's hardware uses a much lower limit, as I've seen this behavior on multiple plane rides, and nowhere else.

              I wonder why they'd intentionally cripple their products. Well, discourage certain uses, seems likely.

        • by gl4ss (559668)

          gps in the phones I've had worked just fine on airplane(civialian transit type of jet plane).

          maybe they canon has shitty chips which turn off at way under the knots/altitude limits.. or just hang on their own.

      • If you don't limit it your device falls under the Wassenaar agreement so it can't be exported from most western countries ... easier to just put in the limitation.

  • by walmass (67905) on Tuesday October 01, 2013 @10:13AM (#45002249)
    In other news, amateur rocket organization Copenhagen Suborbitals recently reported theft of unspecified electronic components from its offices
    • by chinton (151403)
      A more realistic future headline will involve the Darwin Award.
    • Why bother breaking into their offices?

      They are attaching these things to balloons and rockets with parachutes, so there is no telling where they will come down.

      Just watch their website, find where the last GPS recording was sent and go to that spot for a free military-grade GPS receiver.
  • Knock knock.
    Whose there?
    It's the government.
    It's the government, who?
    It's the government and we're here for our GPS units. Hand them over or be labeled a terrorist.

    Look, some high up government person is going to read this, realize that some national security breach has potentially occurred, then send in the troops to reclaim those units. This won't take long.

    Some people need to feel important.

    • by 91degrees (207121)
      Well, I may be wrng, but I don't think Copenhagen Suborbitals is too concerned about the US government. The Danes seem to be a little less paranoid about this sort of thing.
      • Everyone things everything is illegal all the way down to questions like "how are you allowed to build your own space rocket". Well, since its not illegal - its legal.. The world is not that bad... If you play your cards right - work the right channels and diplomacy, many doors will open up...
    • by JustOK (667959)

      Highly unlikely. Everyone has already been labelled a terrorist.

  • And screw the 'authorization'. Switch to inertial nav once an accurate fix is acquired, and use a big enough weapon where getting close is good enough.

  • It's silly anyway (Score:4, Informative)

    by John Burton (2974729) on Tuesday October 01, 2013 @10:16AM (#45002305)
    Given that it's possible to build your own gps received from scratch anyway this seems little unnecessary. (See http://www.holmea.demon.co.uk/GPS/Main.htm [demon.co.uk] for someone who did) Ok so it's not trivial but it's certainly possible.
    • Came here to post something similar.

      It's actually got a bit easier now, since you can get pre-packaged GPS to baseband chips which solve most of the mucking around with high frequencies stuff.

    • by CastrTroy (595695)
      My thoughts exactly. GPS has been around long enough. I don't believe for a second that Non-Friendly governments, or even hobbyists haven't already reverse engineered all the security protocols put into place to stop others from getting an precise location.
      • You need the crypto-keys to be able to access the military channel. Civilian GPS is good, but as has been stated above, does not work at speeds exceeding mach 1 or at altitudes above 60,000 feet.

        • Civilian GPS is good, but as has been stated above, does not work at speeds exceeding mach 1 or at altitudes above 60,000 feet.

          Buy a better receiver that implements it correctly as an AND instead of an OR as the law is written with an AND. Manufactures find it easier to implement it as an or for what ever reason. If you are doing custom electronics for a project such modules are cheap ($25-$30) and easy to find. It is even a selling point that is printed on most (look for ones that state they work above 60,000 feet) and quit trying to use a hacked Garmin, TomTom, or Magellan hand held for this.

          • There is nothing in the code that's an AND or OR statement that can fix this, it has to do with the signals that the systems can receive and decode. Sure, they can receive the military signal, but they can't decode it, because they don't have the encryption keys. I don't think you have a workaround for that.

            • What are you talking about? My comment didn't have anything to do with the well known fact that civilian GPS units can't access the L2 data. My response was about the absurd assertion that GPS doesn't work above 60,000 feet or 1,000 knots. The law is written such that the or should be an AND but most manufactures seem to like to implement it as an OR such that their devices won't work if it is above 60,000 feet or going faster than 1000 knots instead of both cases being true like they should. This has becom
        • by jkflying (2190798)

          It isn't the civilian channel that stops working at 60k feet/mach1, it is the receiver that decides to stop working if it senses these conditions. If you make your own receiver you can bypass these limits.

    • And I assume it is really really easy to hack the commercial ones.

  • This will undoubtedly help them time the drogue/parachute release next time. Unfortunately this failed last time in an otherwise successful guidance experiment [youtube.com] due to the accumulated error in the intertial navigation.
  • This will get you on the Naughty List. Be prepared.

  • A COTS GPS module will give you around 2 meter accuracy. One of the UBlox devices can talk to WAAS and get around 1 meter (supposedly). So my question is: why do they need any better than than?

    And all this is going to do is convince the US government to turn selective availability back on and we're all screwed.

    • Helps to read the article. It's all about height and speed.

  • The actual use shown is with a balloon, so they got the altitude limit raise or removed. It's not clear about the speed limit. Also I don't know about other countries, but I asked some high power rocketry guys in the US about adding active stabilization and was informed that anything along those lines is considered a missile and would not be legal (in the US). Never mind what slashdot chose for a headline then.
    • by Anonymous Coward

      THey, are, however, munitions, and subject to all sorts of restrictions on the information you can disclose. They also might have other operational restrictions imposed by the local FAA office.

      But really, if you start building guided missiles, you attract a lot more attention from the regulatory authorities. Do you REALLY want to have to control all your documentation in accordance with export control rules? Make sure the garage where your missile is stored is locked?

      Not the least is that putting guidan

  • "...removing the limits is a matter of getting into the hardware changing the code..."

    What does this mean?

    • by Anonymous Coward

      GPS modules usually have the limits in the microcontroller code, which is often an ARM chip. So, you get into the hardware, with your software patch.

    • Its not a matter of changing the hardware but the coding inside.... thats were the magic is normally locked
  • by T.E.D. (34228)

    Am I the only one made a little uncomfortable by this?

    Headline from next year: Copenhagen Suborbitals' new franchise office in the Gaza Strip is doing amazing business...

    • Yeah, you probably are. If you've been following Copenhagen Suborbitals for a while you will realize that the only people they are likely going to kill are themselves.

      Mostly harmless.

      • Harming 3rd parties are our biggest concern... besides getting the rockets to fly straight, which pretty much has an potential impact on the first one...
  • What is the 'thingie' that looks like two diodes connected to the 0.47F cap? I can see the cap itsself is a backup power supply. I can see the resistor connected to it is to limit charging current so the inrush doesn't crash other things with the voltage dip. But what is the thingie before the resistor? The symbol looks like two diodes, one of which is shorted out to effectively remove it from circuit and the other simply positioned to keep the backup power from feeding back into the main rail - but then wh

    • Dunno what they are doing with it in that design, but the item is a BAV99 dual signal diode in a 3 pin SMD pack.

      It looks like it is protecting the VCC line from the voltage divider driving the VBACKUP input, which could be done with a single diode, but it might be easier to handle or more reliable.

      • There's no voltage divider. Look at the cap. 0.47F. Not uF. F. It's an ultracap. Stores enough energy to run the GPS for a short time if main power is disconnected. The diode's function is to make sure that if main power is lost, the capacitor doesn't just put energy back into VCC. Given it's function, a low forward drop would be essential for that diode - the BAV is 0.7V, not hugely impressive. A schottky diode would do a better job.

        • Cool. Didn't even pay attention to the units. Makes more sense now. Since these are designed for short usage during rocket flights, doesn't really matter how long it lasts I guess.

  • by citizenr (871508) on Tuesday October 01, 2013 @12:59PM (#45004303) Homepage

    http://gnss-sdr.org/node/50 [gnss-sdr.org]

    You can do software GPS using $10 rtl-sdr dongles.

  • by LoRdTAW (99712) on Tuesday October 01, 2013 @02:25PM (#45005361)

    You can roll your own using off the shelf components. Though this may add a bit of weight if you use PC hardware, an FPGA, DSP, microcontroller or combination may be able to do fast real time positioning past the measly few Hz that vendor GPS modules offer.

    First you need a receiver for the GPS signals:
    https://www.sparkfun.com/products/10981 [sparkfun.com]

    Then you need to process that data into a useful position:
    http://gnss-sdr.org/documentation/sige-gn3s-sampler-v2-usb-front-end [gnss-sdr.org]

    Honestly, applying munitions restrictions to fast GPS does nothing to stop anyone from building a cruise missile or other GPS guided weapons. All it does is impose silly restrictions that rogue nations, governments or peoples will simply ignore and work around while denying peaceful legitimate uses by ordinary people.

If a thing's worth having, it's worth cheating for. -- W.C. Fields

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