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Galmon – Galileo/GPS/GLONASS/BeiDou open source monitoring
- RF_Savage 4y agoAwesome project for checking if there are reported issues with the big GNSS constellations. This goes on a bookmark for future reference.
- xrayarx 4y agoFirst reported 3 years ago with zero comments: https://news.ycombinator.com/item?id=21067915 https://news.ycombinator.com/item?id=21067915 Nice talk about the project by the maker: https://media.ccc.de/v/mch2022-17-how-do-gps-galileo-really-work-how-the-galmon-eu-monitors-all-navigation-satellites https://media.ccc.de/v/mch2022-17-how-do-gps-galileo-really-... Link to html but ultimately a 49min video Very interesting, because it is not just the usual gps talk
- sjaak 4y agoThanks for the talk, I enjoyed watching that
- ahubert 4y agoIt was fun to do!
- xrayarx 4y agoHello there, thanks for your efforts! I really enjoy this happening! Could you please comment on this: https://twitter.com/erikkannike/status/1612729957851054080 https://twitter.com/erikkannike/status/1612729957851054080 How does he track the jamming? How do the russian jam? How could they ever jam up such a large swath? Does that even have a discernible effect on modern GPS receivers in smart phones? Surely it doesn’t effect military systems, they would anticipate jamming, right?
- xrayarx 4y agoNever mind, I found https://gpsjam.org/ https://gpsjam.org/ and the sources are airplanes apparently, or more accurately the API of ADSBExchange
- jjwiseman 4y agoThere's a discussion about GPSJam, which is where he got that map, from a few months ago here: https://news.ycombinator.com/item?id=32245346 https://news.ycombinator.com/item?id=32245346 Sometimes the interference seen on those maps does affect phones, sometimes it doesn't. Coincidentally there's a huge region of GPS (at least) interference this week over the New Mexico area, from a military test. My guess is that people on the ground won't be affected, unless maybe they're very close to White Sands Missile Range between 18:30 and 22:30 GMT. See https://twitter.com/lemonodor/status/1611812892969664515 https://twitter.com/lemonodor/status/1611812892969664515 for more info.
- dark-star 4y agoInteresting talk. At the end he casually mentions so many things that he could also talk about, including that apparently the encryption on GLONASS military signals was already hacked, and that many parts of the mil-spec GPS are "securiy through obscurity"... Is this true? If so, where can I find more reading material about this? It was my understanding that the P(Y) code in GPS is encrypted using (basically) a OTP, and not based on obscurity at all? Doesn't GLONASS use a similar system?
- edent 4y agoI wonder how the crowd sourced data is protected from malicious submissions?
- ggm 4y agoI'm one of the feeds. My window has a high bias to west facing so I only provide partial sky coverage for my region. That said, the whole point here would be not to have single actor dependency. Obviously selective coverage could be turned on but I think blatant misreporting would be apparent. I compiled the git source on my own pi. Bert knows who I am.
- ahubert 4y agoHi! Galmon guy here. This has only once been a problem, someone with a modified firmware, and that produced some exceedingly strange data. In the galmon design, which is quite neat if I say so myself, data is stored per source. If any data is bad, we can throw it out. If someone would really want to mess with us they could of course. But we're probably niche enough that people don't bother.
- captn3m0 4y agoAny plans to support other navigation systems? Would love to help with https://en.m.wikipedia.org/wiki/Indian_Regional_Navigation_Satellite_System https://en.m.wikipedia.org/wiki/Indian_Regional_Navigation_S...
- dark-star 4y agoAre there even any chipsets out there that can receive IRNSS? I don't think the very common u-blox ones can. It seems like only some Qualcom 4G/5G chipsets support it, which are probably difficult to get on a hacker-friendly add-on board, especially outside India?
- captn3m0 4y agoYeah, probably something to reconsider by end of this year. There’s a planned mandate for smartphones to support this: https://www.gpsworld.com/india-mandates-navic-support-for-smartphones-no-timeline-yet/ https://www.gpsworld.com/india-mandates-navic-support-for-sm....
- genewitch 4y agothere's quite a lot of lightning detector systems with nanosecond accuracy GPS onboard. Blitzortung.org is one network of such systems. Should the gps data be shared between these two projects/networks?
- myself248 4y agoMy understanding is that the Blitzortung GPS receiver is the cheapest they could find that provides a good timepulse output, and does not produce the raw packet data dumps that Galmon is interested in. There might be an alternate firmware for it, or there might be a drop-in upgrade from another model in the series, but at that point you might as well just get a real F9P and make it a separate project sitting on the same shelf.
- genewitch 4y agomy system blue has a u-blox. but i don't really know anything about fancy GPS chips, so you might be right.
- puzzlingcaptcha 4y agoWhat's the reason for the offset (~55ns) between GPS/Galileo and GLONASS?
- ahubert 4y agoThat time is hard, I think. So the network itself has needs, you can't just shift all clocks by 55 ns. So instead, an offset is broadcast that tells you what you need to subtract/add to get to UTC.
- gsich 4y agoBut GLONASS-UTC is 1.40 ns and GPS-UTC offset: 0.74 ns? Not sure how those differences add up (or if they should).
- VLM 4y agoTo one sig fig that's 55 feet difference in location. GPS uses WGS84 and GLONASS uses PZ90. "Officially" the difference is supposed to be less than 45 feet all the time and generally less than 15 feet. So, I don't think that's the problem. There seem to be issues with stepping time, and long term alignment seems to be deprioritized over short term quality. Better to have better data today than to have better long term drift over a decade. So all the systems kind of "free run" very close to each other but measurably different. It does not seem that very long term drift adjustment was baked into the cake of any nav protocol, probably because its not navigationally useful.
- dark-star 4y agoCan anyone who knows C better than me explain what the difference is between constexpr double mu = 3.986004418 * pow(10.0, 14.0); which is used in the the explanatory blog post and presumably the code, and constexpr double mu = 3.986004418e14; which is how I would have written it?
- jraph 4y agoI would probably have used the first because it would not have occurred to me I could use the second. FWIW the following prints 1, so it's probably a matter of taste: int main() { printf("%d\n", 3.986004418e14 == 3.986004418 * pow(10.0, 14.0)); } I prefer the second one for sure.
- detrites 4y agoIf you're wondering what this is, a succinct summary from the projects about page [0]: "The internet and the availability of stunningly capable chipsets has made it possible to create a monitoring network that spans the world & successfully receives almost every bit transmitted by the close to 100 navigation satellites currently in orbit." Maybe clarify the above sentence with "an enthusiast-run, open source navsat monitoring network" and perhaps it sums up the project well AFAIUI. [0] https://berthub.eu/articles/posts/galmon-project/ https://berthub.eu/articles/posts/galmon-project/
- ripe 4y agoThank you for summarizing! I think you just saved me and probably many other readers a ton of time, or if we were just going to move on, you provided a good reason to read on.
- gala8y 4y agoWhat are the practical uses for this data specifically? I mean some examples, as I have completely no idea.
- myself248 4y agoISTR the genesis of the project was a days-long Galileo outage, back when it was in "testing but probably usable" phase, and a stark lack of transparency or updates from the folks running the network. But it's not exactly hidden, you can infer quite a lot of things about the satellite status, if you just listen to what they're telling you. The trouble is, they're all over and moving fast, so you need a lot of friends with receivers to feed you the data, then you can put together a picture of the constellation health. Ergo, Galmon. Since then, it's turned out that a bit of sunlight on the operation of all four GNSS constellations, not just Galileo, has revealed quite a lot about their inner workings, availability, and health of individual satellites. One bird in particular was launched into a wrong-but-not-useless orbit by a rocket failure that juuuuust barely got it up there but didn't finish the job. Trouble is, most receiver software assumes the orbits are very nearly circular, and a highly elliptical orbit is both problematic if used for general navigation, and a useful source for testing more robust receiver software that can compensate for it. (Maybe the software wasn't correcting for other satellites' slight ellipsity as well as it could either.) So Galmon provides a view of that satellite's status as observed by receivers all over.
- VLM 4y agoOn a staggeringly smaller scale I had VERY mixed results with storing data points that look like (satellite ID, timestamp, el, az, signal strength) and then doing a data analysis to map out "anomalous attenuation" by el,az (kind of a bistatic radar display). "Everyone knows" since day 1 of GPS back in the 80s that tree leaves and rain storms ruin GPS reception, but rather than complaining about it and/or avoiding it, why not use it as a data source? Turns out I had trouble pulling a useful signal out of the noise. Maybe with a lot more data or a lot more RX running in parallel or ... There are of course inherent limits as discovered by Air Forces over the decades where bistatic radar works best directly overhead whereas I was interested in "storm clouds on the horizon" exactly where it didn't work. I had some optimistic imagination in that if heavy rain causes 30 dB of attenuation, then extreme data analysis might indicate something as trivial as cloud cover, or even fog, might cause 0.01 dB of attenuation and I could map out regular non-rain clouds or something. That data could not be pulled out of the noise. Very optimistically, if I placed antennas on corners of my property, I could "edge detect" even if the signal level varied randomly-ish by comparing the multiple RX and doing some trig. I live close enough to an airport that occasionally a plane should be between me and a satellite. That did not work either. Anyway, the linked distributed project is my merely a thousand times larger than my playing around experiment.
- ck2 4y agoI love playing with GPSTest on various phones to see what newer chipsets are doing. I'm more interested in altitude accuracy than position which seems to be a challenge for GPS It's odd to me that most devices support/trust GLONASS which shouldn't be trusted while not (yet?) supporting/trusting Beidou (like Garmin watches have no Beidou support) neat https://upload.wikimedia.org/wikipedia/commons/b/b4/Comparison_satellite_navigation_orbits.svg https://upload.wikimedia.org/wikipedia/commons/b/b4/Comparis... network comparison https://en.wikipedia.org/wiki/Satellite_navigation#Comparison_of_systems https://en.wikipedia.org/wiki/Satellite_navigation#Compariso... Is there a 3d realtime model online of the earth that shows where every satellite is? Would be an interesting project if doesn't exist yet.
- mastax 4y agoYeah, phones seem to have really good GPS receivers, even when you turn off all the network assists. Even with their tiny antennas they're at least comparable and sometimes better than my expensive uBlox GPS with a large active antenna.
- focusedone 4y agoHadn't heard of GPSTest before, thanks! Annnnd there goes another app into my 'toys for waiting in lines' folder.
- toast0 4y ago> It's odd to me that most devices support/trust GLONASS which shouldn't be trusted while not (yet?) supporting/trusting Beidou Russia requires GLONASS support, so a worldphone needs it. China requires a lot of things, so a worldphone isn't going to work anyway.