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We built a new GPS receiver engine
- PaulHoule 6y agoFor a drone to be affected by GPS speed limits it would have to be a hypersonic drone.
- rrmm 6y agoA super-duper drone?
- miahi 6y agoThere are two limits: 60000ft and 1000 knots. Some manufacturers use "AND" between them, others use "OR"[1]. So you can have faster drones if you manage to stay below 60000 ft. [1] https://ukhas.org.uk/guides:gps_modules https://ukhas.org.uk/guides:gps_modules
- naz 6y agoWhich is weird, because something traveling at 1000kts at 100ft seems scarier than something doing 1000kts at 60000ft.
- loeg 6y agoSomething traveling 1000kts at 60000ft can reach a target at 100ft. The legal guidance has ICBMs in mind.
- Accujack 6y agoOnly if you're military or part of the government in the US, because civilian drones have a 100mph speed limit and a line of sight requirement.
- implements 6y agoSome manufacturers have imposed lower limits eg some older Garmin handhelds won’t display info at speeds over 90 mph, though they still maintained a fix. I believe it was to stop people using them in light aircraft.
- miahi 6y agoThat's probably because Garmin also makes avionics and flight systems, so they just segmented the market.
- brokenmachine 6y agoI have a Garmin GPS watch for jogging, and it worked fine at 700kph during a flight. Really helped my monthly average running speed.
- Rebelgecko 6y agoThe US got rid of the altitude limit a few years ago, and increased the speed limit to 600 meters/sec (about a 12% increase)
- sevenf0ur 6y ago> Well, how about deliberate dilution of precision or intentionally limiting the speed the GPS chip can be used at? Is that a legal requirement or just done on request? I sort of chuckle whenever I hear of limitations like that being put in place as if someone that can construct an ICBM is going to be constrained by the GPS module.
- jimhefferon 6y agoIt was required. But that was gotten rid of by the Clinton administration. See https://www.gps.gov/systems/gps/modernization/sa/ https://www.gps.gov/systems/gps/modernization/sa/ .
- deleted 6y ago[deleted]
- loeg 6y agoThe thing you're thinking of is true, but there are still speed limits on commercial GPS chips to prevent their use in missile guidance systems. TFA seems to be clearly flouting that law, so, good luck to them.
- hjb 6y agoIf you dig into their website, they appear to be based in Singapore and Japan. I've no idea if those countries have similar laws.
- londons_explore 6y agoUS law applies worldwide when it comes to this sort of stuff... You can bet if you started producing these chips and selling them to Iran, you would either be arrested and child porn found on your laptop, or have an 'accident'.
- opencl 6y agoThey indicate plans to sell hardware on Crowdsupply which is based in the US. Presumably this is going to be FPGA-based which brings up all the fun questions of how ITAR applies to software. Would adding a speed restriction in their VHDL that could be trivially bypassed by patching out one line of code satisfy ITAR requirements? AOSP has this sort of code in it (search for ITAR_SPEED_LIMIT): https://android.googlesource.com/platform/frameworks/base/+/master/services/core/java/com/android/server/location/GnssLocationProvider.java https://android.googlesource.com/platform/frameworks/base/+/...
- cozzyd 6y agoAffordable differential GPS would be a nice application... it just requires a fast way of synchronization between two devices (CW in the ISM band would probably work, for example).
- Accujack 6y agoRTK gps is better and quite affordable now. Look it up, you can use two receivers costing maybe $15 each for it.
- detaro 6y agoDo you happen to know a good introduction to how one would use it? I've looked at tools around it a few times, but always didn't find the point where it made "click" on how to actually do anything with them.
- jpm_sd 6y agoYes! Check out this awesome blog. https://deepsouthrobotics.com/2017/04/20/spilling-the-beans-on-rtk/ https://deepsouthrobotics.com/2017/04/20/spilling-the-beans-... https://deepsouthrobotics.com/2019/06/03/the-taming-of-the-u-blox-zed-f9p/ https://deepsouthrobotics.com/2019/06/03/the-taming-of-the-u... https://deepsouthrobotics.com/2019/05/23/piecing-together-an-autonomous-mowing-rig/ https://deepsouthrobotics.com/2019/05/23/piecing-together-an...
- detaro 6y agoThank you!
- danisth 6y agoYou set up the base station over a known point, and now your rover unit can give you cm level accuracy when it's within range of the base station (UHF radio range generally). For a practical application, let's say you wanted to lay out crops for a small hobby farm. This can make getting your base station set up, because you might not care as much about absolute location, which would require finding a surveyed benchmark. Instead you put your base exactly on the corner of your plot, and after setting up a local grid system you can now exactly layout your farm according to your plan. You simply walk around with the rover unit and can get real time cm accurate "coordinates."
- myself248 6y agoThis is gonna be the next step after Andrew Holme's 100% DIY receiver: http://www.aholme.co.uk/GPS/Main.htm http://www.aholme.co.uk/GPS/Main.htm
- coopsmgoops 6y agoBlack magic as far as I'm concerned
- cozzyd 6y agoI am curious what timing precision they are achieving. You can easily get ~10 ns with cheapish GNSS modules.
- willis936 6y ago10 ns is the quoted accuracy, but it’s not easy to verify that and it is very easy to mess up something at that timescale. If something is cheap, I’d be willing to bet their PPS output is not going to be 10 ns accurate. Most applications won’t tell the difference between 10 us and 10 ns accurate, but when you need it, you’ll know it.
- rrmm 6y agoThe jitter can be a really important parameter. for example in pdf: https://processors.wiki.ti.com/images/f/f1/TI_GPS_PPS_Timing_AppNote.pdf https://processors.wiki.ti.com/images/f/f1/TI_GPS_PPS_Timing...
- willis936 6y agoMy masters thesis is on jitter measurement techniques in 25 Gbps baseband signals :) Jitter can be tracked and filtered in PPS signals. The related parameter, wander, is interesting to me. Phase noise above 10 Hz is jitter. Phase noise below 10 Hz is wander. Why? ¯\_(ツ)_/¯ Allen variation is the typical metric for wander.
- e-_pusher 6y agoFascinating! Do you know of any good textbooks or application notes that go into jitter measurement techniques? I found this note from Keysight, is this is a good place to start? http://literature.cdn.keysight.com/litweb/pdf/5988-6254EN.pdf http://literature.cdn.keysight.com/litweb/pdf/5988-6254EN.pd...
- willis936 6y agoThat note is interesting, but a bit dense and most of it is standard specific implementation details that aren't too important without first understanding why the standards were written the way they were. That question isn't usually well documented, so a bottom-up understanding of the testing is valuable imo. If you want to become a time-nut, then check out time-nuts[0]. They know their stuff and will be the most valuable resource on topics related to GPS timing: wander, allen deviation, and jitter of various sources (quartz oscillator vs rubidium, etc.) I will say that the big test and measurement (T&M) players (Keysight, Tektronix, Rhode&Schwartz) have been the main drivers of T&M research. It's a strange field where academic work and commercial interests line up, so all of the academics work for commercial companies. They'll happily share their results and preferred approaches (except for the secret parts) in white papers and app notes. I don't think there is a good centralized repository of such documents, so it may require some hunting. Knowing keywords might be helpful. If you're mainly interested in jitter then hot things to search for are "jitter", "jitter decomposition", "TIE", "wander", and "dual-Dirac" (just off the top of my head, I'm sure the rabbit hole goes deeper if you start digging into more recent work). I was in T&M for 7 years. I'm not currently but likely will be in the future. This[1] is the bible I learned on. It's $120 new and not too easy to find free (most of the people who would find it interesting can afford it, ie not in curriculum). Most of my learning was through osmosis over the first few years, then I taught myself the rest. I only used the book as a reference after the first year, but I wouldn't say I knew it all until maybe 5 years in (I was a student at the time too). When I flipped through it towards the end of my time I found it was a good teaching source. I suffer from the curse of knowledge, but I think if you have EE chops then this book will make perfect sense and even help build the intuition necessary to be a good test engineer. The book is all practical T&M techniques for high-speed SERDES, so wander is outside of the scope of the book. There are other bits in the book besides jitter too (lots of tasty stuff on encodings and impedance). 0. http://www.leapsecond.com/time-nuts.htm http://www.leapsecond.com/time-nuts.htm 1. https://books.google.com/books/about/An_Engineer_s_Guide_to_Automated_Testing.html?id=tm-uDgAAQBAJ https://books.google.com/books/about/An_Engineer_s_Guide_to_...
- app4soft 6y agoFTR, Here is document about design of a Bluetooth GNSS receiver.[0] [0] https://github.com/lpechacek/u-blox-gnss-receiver https://github.com/lpechacek/u-blox-gnss-receiver
- sitkack 6y agoDo any of these systems offer a way to cryptographically prove that a signal was received at a specific place and time?
- hylaride 6y agoI don't think (American) GPS currently supports that for the civilian signals, though IIRC Galileo does and there are plans for the American version to support it in the future. However, GPS signals are essentially just the location of the satellite with a time stamp. There's nothing to prevent the signed signal from being re-broadcast a short time later to mess with location data. The Russians have (allegedly) been doing this in the Black, Baltic, and Berants seas the past few years.
- gsnedders 6y agoDon't believe it's yet publicly available for Galileo, but yes, it's meant to be going live soon. (And note that the authenticated stream is a paid for service.)
- centimeter 6y agoThat's not something you can cryptographically prove, unless you have an extremely loose definition of "cryptographically", like "some computer with an SGX private key said so".
- brokenmachine 6y agoIs that even possible, and what would be a use-case for that?
- ISL 6y agoThoughts on how this sort of thing, even though CoreSemi is Singapore/Japan-based, might fall afoul of US ITAR restrictions? As a scientist, open hardware is the best. I'm just not sure whether or not CoreSemi might have put its foot in something bigger than they know.
- stagger87 6y agoMost commercial/civilian GPS equipment is not controlled under ITAR anymore, the EAR is more relevant here.
- ur-whale 6y agogithub links in article don't seem to work, but this does: https://github.com/CoreSemi?tab=repositories https://github.com/CoreSemi?tab=repositories
- jwineinger 6y agoThey messed up the HTML and made two links there: "https://github.com/coresemi/gnss-" https://github.com/coresemi/gnss-" incorrectly links to https://github.com/c https://github.com/c, while "baseband" correctly links to https://github.com/coresemi/gnss-baseband https://github.com/coresemi/gnss-baseband.
- durkie 6y agoMostly off-topic here, but it seems like the best place to get an answer: several years ago in my lab at Georgia Tech, a technician I worked with said he had a friend who invented a device for doing celestial navigation, but that it 1) worked in the daytime somehow and 2) used digital technology so that it was more precise than a sextant / traditional celestial navigation. The technician was prone to a bit of exaggeration, so I'm not 100% sure that this is real, but I'd love to find out more if so.
- jascii 6y agoOne of the most common celestial navigation methods is through a "noon sight" measuring the angle between the sun at its highest point in the day and the horizon. So that already works in the daytime. One of the main reasons to practice celestial navigation is to have a backup in case electronic systems fail (all that salt water and all..) So I'm not so sure about using a "digital system"..
- AWildC182 6y agoThis is real. It's used a lot in defense applications.
- sho 6y agoThey used astro-navigation as far back as the SR71, the "guidance group" system nicknamed R2D2. Cool video of a pilot talking about it here: https://youtu.be/CeBu6mRDaro?t=3180 https://youtu.be/CeBu6mRDaro?t=3180
- wiml 6y agoNot just exotic aircraft! Celestial navigation was used by all kinds of long range aircraft, military and civilian, until the 1960s or so. Early jetliners (including the first models of the 747, for example) had sextant ports in the top of the fuselage; older aircraft might have "astrodomes". There's a continuous line of use from age-of-sail seafarers to jet-age aircraft. I think the military trained with sextants for air navigation until the 1990s, as a backup method for inertial and satellite. The main difference being that star sights were taken manually, with an instrument and an eyeball, instead of automatically like the SR71. Of course satellites did and still do use star trackers. The Apollo astronauts took star sights too, presumably for orientation rather than position.
- kayson 6y agoVery cool but a far cry from an actually usable open source hardware receiver. Implementing the RF front end is not at all trivial and highly dependent on the manufacturing process, which is probably why they didn't release one. There's also the issue of fabs all requiring NDA's for their PDK's (process development kit), and transistor-level netlists would probably leak some of that information. It would be great to see an open PDK at something like a 65nm or 40nm node which would really allow for open source hardware design.
- azinman2 6y agoIt seems like they did this for SpaceChain, which I had never heard of before. I read their information, taking about combining blockchain-technology and satellites, and I'm still very confused. Other than buzzwords, what is this actual business and why is the blockchain necessary here? dApps in Space? What? Why?
- rasz 6y agoattracting VC suckers of Softbank caliber
- deleted 6y ago[deleted]
- ChuckMcM 6y agoThis is super cool, its nice to see this come out of the idea stage into something one will be able to buy. I find the most use for gps modules is time data, I have one outside my window that is feeding a PPS signal into a server running ntpd. Saves me from bothering internet ntpd servers.
- mNovak 6y agoGreat, maybe now we'll finally get $10 Chinese RTK modules