Note that this isn't a GPS failure, it's a failure with Inmarsat's Satellite-based Augmentation Systems (SBAS), which supplements GPS data with signal measurement errors corrections. This allows for centimeter level positioning.
Sea ports used to broadcast a local correction signal[1] back when GPS was intentionally less accurate. Seems like an oversight that farms don't have their own correctors.
Farms easily could. You can get GPS RTK kits that cost less than $1k and you could set that up at a central location, with wired power systems, etc.... it could calculate its own position down to the centimeter, and then you could use that to help provide correctional information to other clients.
SparkFun has some kits in this space, but you can easily pay up to $10k or more for a more commercialized system that is designed for surveying, or other related purposes.
Aren't there public RTK ground stations already covering most landmasses? I've used a few RTK receiver modules and always got centimetre level accuracy without having to buy an actual station. Was that actually SBAS data or what? I'd always assumed that SBAS was slow and only used by those geodesic receivers that get planted for an hour to refine their position down as much as possible.
If that's really true then what the was even the point of building Galileo HAS then? I swear these things could not be more confusing.
Australia does have a public RTK network, which is free to access - you only have to ask. But you need internet access, and RTK only works is you are within 20km or so of the base station.
As other have said can do a local install. A pair of RTK receivers is only $500. But you need a connection between the base station and the tractor. These farms are pretty flat so perhaps perhaps technically it's not so difficult with LORA. But these are farmers, not hackers, and perhaps it has to talk to the tractor, and perhaps the tractor is made by John Deer. It all gets very hard very quickly.
In the mean time SBAS was a off the shelf solution the dealer could sell to everyone because it worked everywhere in the country. Until it didn't.
Yeah, my state's Department of Transportation runs a GBAS/CORS network and anyone can have access to it just by asking.
Trouble is, that (and Galileo HAS) assumes you have internet access. Maybe you're so far out in the middle of nowhere (This is Australia we're talking about in TFA) that the internet isn't available, or reliable.
So maybe you think satellite-based corrections are the way to go, but I concur, a local RTK reference would also work. (But 99.9% of the time, the satellite service is gonna be less hassle.)
Phones and other devices with cellular radios still use differential GPS by way of the cell towers (which have known, fixed positions) to do those corrections. You can notice this because, when you don't have a cell signal, your phone is considerably slower to get a GPS lock and less accurate when it does. Presumably these farms are out in the middle of nowhere and so that's why they can't do the same thing and need a satellite-based augmentation instead.
Not quite. Phones use assisted GPS, which means that they download GPS ephemeris data over the internet instead of getting it from the the satellite signal (because the satellites transmit data at 50 bps). So the time to first position is faster.
Differential GPS, by contrast, transmits the difference between the surveyed location of a base station and the GPS-derived position of the same station. That offset can be used locally to correct other nearby GPS receivers.
Phones also use trilateration on the cell tower signals to get an approximate solution before trying to solve 3d+time on the GPS signal.
Most modern cellphones use AGPS, assisted GPS, to reduce the time to get their first fix. Basically, AGPS primes the GPS receiver with an accurate time of day and the GPS almanac (satellite ephemeris data). That's rather different from Differential GPS, which is basically corrections used to compensate for fluctuating conditions in the atmosphere.
I may be wrong, but I don't know of any system for cell-tower derived corrections being redistributed out as GNSS corrections. Could you clarify the specific system you described?
A-GPS can run in Mobile Station Assisted (MSA) mode, where the device sends raw GPS data to the A-GPS network and the assistance server processes it. In this situation, the assistance server can use whatever precise cell site location and ionospheric correction data it wants in its processing, although this is more of an "exercise left to the implementer" and I'm not sure sure MSA mode is even very common anymore.
I think was only a brief window where MSA was used, when phone processors were weak and cheaper to have limited GPS chip. Now, GPS chip do everything onboard and are included on radio processor or main processor. Plus, phone processors are powerful enough to do GPS themselves.
Not so much. Modern GPS will get a first fix pretty quickly regardless, you don't need to seed it.
AGPS is used when satellite coverage is poor, like urban canyons in a city, also a situation where there are a lot of cell towers and triangulation is somewhat useful
AGPS refers to a specific set of technologies, MSB where the almanac and time seed is provided over the cellular network, and MSA where the unit sends GPS data to the AGPS server and the server solves for location using whatever data it would like (which can include a multitude of corrections).
I think what you're referring to with cell tower triangulation (and also WiFi location, etc.) is generally referred to as "hybrid location service" and is usually done at a higher level (ie - in software) using AGPS as one input to a sensor fusion algorithm.
The time to first fix is mainly impacted by whether the receiver knows which satellites to listen to. This requires two things: having the ephemeris for the constellation (either 10min of listening to GPS signal, or getting that through AGPS), and it's approximate own position/time (done through cell antenna locations, and NTP) to know which satellites should be visible.
Once this is available, the receiver can then focus on the signals that are expected and will then be able to provide a 3D fix as soon as it receives something from 4 satellites, which would be in a few seconds.
> Presumably these farms are out in the middle of nowhere and so that's why they can't do the same thing and need a satellite-based augmentation instead.
Easily maybe.
I can’t see any reason someone can’t take a stationary GPS enabled device and use that to broadcast the differential between received location and actual location. Probably could do it for less than $20 in equipment. Add multiple units and get triangulation for free.
> But two important things have happened since then. Australia has moved about 1.6 metres northeast, effectively moving the location of mapped features and their associated GDA94 coordinates.
> At the same time, positioning technology has evolved considerably. By 2020, Australia will have moved by 1.8 metres and many of us will own devices that could pinpoint locations with accuracy as small as, well, a smartphone. With real-time access to precise satellite positioning at our fingertips, we’ll notice discrepancies with GDA94-mapped features.
> Imagine the confusion if a driverless car can determine its coordinates with (say) decimetre accuracy, in the GNSS datum, but the stored map features were referenced to our old datum GDA94 and and were nearly two metres different. That’s probably not even in the same lane.
As I understand it, RTK nulls that out. If your RTK base is fixed to the landmass that's moving, your rover positions will move right along with it. So a farmer with an RTK base stuck atop their silo or whatever should be fine.
Interesting that whatever technology underlies the SBAS system isn't just integrated into GPS. It would be nice to be able to map property lines with just my phone.
The US government does provide an SBAS called the WAAS, operated by the FAA. It's also had a hand in designing and operating a number of other augmentation systems [1], including CORS, GDGPS, and NDGPS. As an aside, don't you just love how many government acronyms there are?
Wasn't saying it did. MSAS (Japan) can be used in AU if you accept the performance degradation, but the lack of a public SBAS for the southern hemisphere is a big reason why SouthPAN is being brought online.
It seems that GPS signals can be used for higher accuracy if the receiving equipment uses two frequencies instead of one. This can freely be done by civilians, but requires more expensive equipment. Perhaps this solution with SBAS requires a cheaper setup?
Multi-frequency GPS is already available in many inexpensive civilian devices such as smart watches and cell phones. It improves accuracy a little, primarily when the device doesn't have a clear view of the sky like when next to buildings. But it's still not as precise as SBAS.
The highest precision GPS receivers require dual-frequency reception and perform "carrier differential GPS" - any time people are talking about GPS with 2cm accuracy, that's what they're talking about.
The GPS signal has a digital signal (with a wavelength of ~300m) modulated with a sine wave (with a wavelength of ~20cm) - you can measure the 20cm signal much more precisely than the 300m signal, but it's 'ambiguous' because it repeats every 20cm and you don't know how many waves of the sine have passed.
If you can receive two frequencies, giving you two slightly different sine waves, you can multiply them together and get a sine wave with a longer period, which (together with some clever maths) lets you bridge the gap between the unambiguous-but-imprecise digital signal and the precise-but-ambiguous sine wave.
You also need a fixed base station at a known location - or access to a commercial network of such stations.
You can use the cell towers to assist in mapping it correctly too as they are fixed position and the location is well known. Pretty sure the QCOM patents on it are out of patent by now. Not sure if the android/ios api will expose the whole list of towers the chip can see though. The chip can do it though.
There are GPS RTK systems designed for use by surveyors. They can cost over $10k, but you can also get much cheaper kits that you can put together yourself from SparkFun -- like less than $1k, easy.
This isn't 1993 anymore. Beidou and Glonass (and Galileo) are global networks that do the same things for those other countries, and the ITAR restrictions on GPS receiver altitude and velocity are increasingly able to be overcome by a hobbyist in a garage, much less a nation-state.
Not quite. Geodetic GNSS systems use two different carrier frequencies to measure and correct for atmospheric dispersion. This reduces the error to sub-mm levels. The inaccuracy of real-time GNSS is due to unknown variations of the satellite orbits, satellite clocks, and earth rotation.
Seems one could use GPS for less granular positioning and then use visual landmarks like the soil/crop edge from the prior pass or row locations to align for the next pass.
On /r/farming yesterday someone was showing how he uses John Deere's AIG (Active Implement Guidance) to come back after seeds have germinated and basically put "pockets" in the ground to allow water to pool around the seedlings. The accuracy that it requires to do that without damaging the plants is amazing.
It's probably something that pays for itself reasonably quickly too. Minor human wobbling means more difficulty and damage when harvesting, probably a wasted row or three per field, etc. Add that up over a decade and many, MANY acres of fields and it's probably a lot of money.
I am designing an autonomous farming robot. You're not wrong that this is possible, except in a large field, crop rows would move over time if you were using them as a visual reference, and it could be non-obvious which row you are in from visual features alone.
The bigger problem is that computer vision is hard and expensive, while doing differential GPS is less expensive and much easier. I made our robot fully autonomous for development using only differential GPS, and we are working now on adding a vision system. A couple of GPS receivers and some very simple code is just easier to manage.
Hey, I just got some land in N. California and I was wondering about building a robot like yours to work it. It looks like I might not be able to get up there personally for a bit (family obligations) so a tele-operated robot might be the way to go. (Also, I'm a hobbyist robot maker, so... yeah. Robots!)
The land I just got is for a mutual-benefit non-profit corp I started (Ariadne Systems) to do pretty much exactly what you describe!
> ...you can ensure that everyone gets fed etc without paying for it by building an economy where everyone is part owner of the productive machinery they depend upon. Then no one is poor. Creating an economy where a preponderance of the firms are cooperatives is a good start. So this can be done in a traditionally libertarian way, without high taxes or strong government intervention.
The corp I started is just such a cooperative firm (well, it will be once I find some people to cooperate with, eh?) to co-own the productive machinery and ecologically-harmoniously agriculturally-productive farm land, and provide goods and services (and eventually homes) to the members.
You got it. We just canceled Netflix and Hulu and I don't see why that money shouldn't be redirected to your project.
My desire is to get productive on the land (as in make some money) ASAP. Ideally it can pay for itself starting now.
Before I go off on a big ol' stream of consciousness brain dump, let me ask you, what about a scenario where you provide me with one of your kits (free or at cost maybe?) and I agree to give you, say, 15% of gross sales of produce raised with your machine? You would retain ownership of the machine, I would be responsible for maintenance and repair. Something like that? It just occurred to me so I haven't thought it through yet. (I can raise the question on your forums if you like? I just joined.)
Anyway, like I said, I want to make money on this land. I very much want it to pay for itself, I really want to avoid getting another programming job (now that the machines can talk and program themselves my heart isn't in it anymore.) And it would be fantastic if I can make enough money to fund all my grand ideas (including robots.)
I'm developing a plan (the purchase was kind of sudden) in roughly three phases:
I) collect and sell stuff laying around. Rocks, wood, etc. I am jealous of that matériel but it's a quick and easy way to make a few grand to fund the next stage.
II) SPIN (Small Plot INtensive) market gardens. ( https://spinfarming.com/ ) If i give over an acre or two to SPIN plots and figure out how to reach markets I should be able to make $50k-$100k per year easily.
Neither of the above are regenerative. The whole point is to fund:
III) Food forest. I figure you're hip to that already, but I want to share a video I just saw last night "From a Dry Field to a Lush Food Forest in 18 Months" https://www.youtube.com/watch?v=icJx01VuV6I So there it is: if you have the resources you can do that in 18 months. (I have many of the species he mentions already in my seed box! Now I have room to germinate them! Que mad scientist laugh. I have about four hundred species of seeds ready to go.)
Food forests not only produce, uh, produce, they also grow the seeds and cuttings etc. to make more food forest. (I've had people ask if regenerative ag is scalable. Yes, it is scalable. Life scales. That's like it's whole deal. That and being gorgeous!)
Long-term I want to have a botanical garden, a tropical conservatory, ponds and water systems etc... It's gonna be great!
> You got it. We just canceled Netflix and Hulu and I don't see why that money shouldn't be redirected to your project.
I would love that thank you so much!
This is all great stuff to post on the forum! It is hard for me to engage with everyone about the project because I am doing so much stuff, but I also want other people to see the enthusiasm our project generates.
> what about a scenario where you provide me with one of your kits (free or at cost maybe?) and I agree to give you, say, 15% of gross sales of produce raised with your machine?
Thank you for the suggestion. Our project is moving slowly. It will be some time before we are able to ship kits, and even when we do the plan is to ship them without tools. Its going to be a long but worthwhile road to profitable farming with these machines.
I love everything you're saying tho. Welcome to the community!
Hey Taylor, I joined the community and posted an introductory, uh, post, but I seem to be in a "pending moderator approval" limbo. I know you're busy but maybe you could clear the flag, or whatever, to let me participate?
How will you handle this case (which while not common exists). Farmer goes in and buries irrigation pipes with underground emitters - these pipes are expected to last for 5 year or so (I don't know what the actual lifespan is - I know they are replaced every few years, but I don't know the actual schedule). Each season the farmer smooths the grounds, and plants each row exactly above the pipes in the ground.
Can your visual navigation system figure out where those pipes are each year to within 2 cm? visual geographic features are going to change a lot over the years - the local ground is smoothed out every year, trees (if any) will grow or die, fence posts will be replaced...
Assuming equal spacing, you only need landmarks (survey spikes) on the first row. Then use the implement impressions from the first pass. But I see your point.
Visual surveying within and over Australia is hard (source: a few decades of Australian geophysical surveying practice) .. wide area ground shots from 80m altitude (low altitude aircraft) look extremely similar across large areas making feature picking for location improvement difficult.
In an agricultural setting Western Australian grain fields are hundreds of acres in size across relatively flat landscapes .. it's a sea of waving grain to the horizon in all directions from tractor height.
While there are locations that have distinct visual features it's no universal panecea and won't offer the cm accuracy desired.
Katie McRobert, general manager at the Australia Farm Institute, said Australian farmers sourced their GPS signal from one satellite, which was a critical risk to rural industries.
All that went out the window when the Inmarsat-41 satellite signal failed.
Can somebody who actually knows what happened fill us in? Because saying you depended on one satellite for GPS makes no sense. Based on the article as-written, this is headline is wildly misleading. The tractor failure has fuck-all to do with GPS. It sounds like their satellite data link failed and the tractors shut down without a control signal.
It's a commercial GPS correction service. It corrects for atmospheric conditions which affect RF propagation slightly. There are many ground stations which receive GPS. They send correction info to an uplink station which rebroadcasts corrections using a geosync satellite. These services are regional, not worldwide, since they need ground stations and a geosync satellite with the right coverage.
It's not free; there's a substantial subscription charge. Here's one that works in the US.[1] We used Novatel's for the DARPA Grand Challenge 20 years ago.
Naïve question: it's a farm, you own the land, it's mostly flat, I'm wondering why there isn't any "deploy your own positioning service on a bunch of high poles" product?
The John Deere RTK Radio 900, which does exactly that, costs about $1000 used. You put it on a tripod next to the field, or on top of a building. If you want season to season repeatability, it has to be in the same place. This is GPS correction, not a completely standalone navigation system.
There are more components for big farms. There are repeaters to re-broadcast the correction signal, which in the US is in the 900MHz ISM band. Some Deere dealers have their own stations throughout a farming community. There's a fee to use that.
It's like having your own server instead of using "the cloud". Works fine, takes more attention.
"To put together a one-inch accurate RTK system for John Deere tractors, you start with an Autotrac automatic steering kit, which is $5,040 plus installation costs of $1,200. Then you add a monitor. John Deere offers three monitors: the basic Greenstar display for $1,700, Model 1800 colour display for $2,250, and Model 2600 touchscreen display for $6,294."
"The standard receiver with StarFire 1 capability is $3,144. That gets you accurate to within eight inches either side of the desired path. To move up to StarFire 2 and its sub-four-inch accuracy, you need software upgrades: $5,040 for the Autotrac software upgrade and $2,500 for the receiver software upgrade."
"To go from SF2 to RTK, you need a receiver that includes a radio to communicate with the RTK base station and with the satellites. This costs $1,695. You also need RTK activation, which costs $3,780."
"Add it up. From square one, with the top-end monitor, you’re looking at around $30,000 to equip the tractor for RTK. But wait. You need a base station. A two-channel base station will cost another $15,000 or so."
> Can somebody who actually knows what happened fill us in? Because saying you depended on one satellite for GPS makes no sense.
I have no real knowledge of this, but maybe they were relying on that satellite to transmit DGPS corrections for their region or something, to improve accuracy.
Edit: Found this while replying to a now-deleted comment:
Even if it's not exactly DGPS, it seems like it's some kind of accuracy-improvement service:
> He has got a workaround for now, using the old free-to-air GPS that is a lot less accurate, but he said he was disappointed with the lack of information on the outage.
IIRC, regular GPS positions have an error of at least a few meters, which is not good enough if you're trying to plant crops.
The article does say that without the GPS service, they are 4% less efficient (in terms of slightly overlapping swathes of seeds/fertilizer/whatever) and this is enough to be uncompetitive. Back when I was a kid on a family farm, accurate within 4% would have been great (with manually driven tractors)!
Seems like this level of hyper-optimization being required out the gate is more a problem in and of itself.
Call me a luddite; but if we're at the point that one needs bloody GPS to remain competitive, I'm beginning to question the resilience of our food production system as integrated with the global market.
Everyone needs food. Period. If you can't get that food from where you grow to somewhere that needs it, that sounds more like the problem that needs solving.
Then again, I think practically every problem reduces to logistics problem if you dig deep enough.
This is not the USDOD GPS. This is Inmarsat's DGPS service that provides ~1-2cm accuracy. Which, if you're driving between rows of produce can be the difference between harvesting or crushing crops.
Nothing insurmountable. You need a receiver that supports RTK. Typically the hardware receiver can do it but you have pay to unlock the functionality (typically about 3000 USD per device). You need an RTK base station (or one you can use that's not too far away) and a way to get the correction signal (local radio system or over Internet with cellular data).
With DGPS corrections, like you get with the satellite that failed, you get about 10 cm positional accuracy. For dryland crop farming, that's often good enough. It is more accurate than what most human operators can achieve and reduces operator fatigue. So many ag GPS systems are setup to use it out of the box.
There are other solutions, in addition to RTK. Trimble has "CenterPoint". There are Omnistar corrections (different sats, better accuracy than DGPS). Novatel has "GLIDE" but I've never seen it in use.
What an insane dependency tree, that driving a truck in a field to plant some seeds requires a computer operating in space. I really hope there is a push-back on this unbounded complexity. Mind boggling.
It's only silly if you have an outdated "romanticized" image of farming in your head. Those images are from a time when >50% of the population farmed. Technology is what has enabled the vast majority of people in developed societies to do things other than farming.
I'm sure someone was scoffing at how "ridiculous" it was the first moment a farmer took a Tin Lizzy into the field and it needed a new clutch. Technology "in the field" is so normal that it is an idiom.
Yes, and that divide includes genetic engineering, weather satellites, teams of chemists, million dollar tractors, a finance and logistics infrastructure, and a whole lot of other stuff that doesn't look anything like American Gothic. GPS guided tractors are not remarkable in that continuum.
this thinking in the previous industrial age created the poison wastelands of Ohio. Mudslinging with the tag "American Gothic Farming" adds to the arrogance of it all. American farming is largely a flaming disaster on top of destruction, with other would-be plantation owners racing to copy it. Plenty of blame to go around, and this contrite endorsement of all and anything futuristic, ain't the cure.
It just struck me that this solves Graebers useless jobs puzzle! If humanity survived and evolved when there was no time for other jobs non of the other jobs are useful. There was a time before farming too! Imagine that! What a paradox!
Reminds me how we technologied all of the fish out of the water and pretended we got more fish that way.
On the other tab I just learn that trusted publishers are a mechanism. Plants are mechanisms too! If you let them struggle without helping them they will figure out a way. Even if you help them you (the human) are not growing the plant. If you open the curtain you are not rising the sun. The plant grows the plant. We've done a great job making it dependent on our nm technology. It's now pampered, weak, lazy and addicted to convenience. We've made food in our own image. If it could talk it would disagree with me and praise socialism.
> What an insane dependency tree, that driving a truck in a field to plant some seeds requires a computer operating in space.
Well, what if I told you that, if GPS failed, many other (stationary!) operations would be impacted? Including financial.
We rely on space computers for more than position, we also rely on them for accurate timekeeping. If you are connected to the internet you can get time corrections that way, but there's plenty of devices that are gathering time data from space.
Now, the issue here is not so much that they are using satellites, is that they are _only_ using satellites (and, it would seem, they are using them for the entire time they are operating). Land-based stations around the field to provide location information could definitely be used instead. Or other mechanisms.
I don't know if tractors have inertial navigation units but, if not, maybe they should. That would at least allow them to operate after the initial fix was established (which doesn't even require GPS, just a well-known starting point). Basically, the same thing that airliners already do.
One can imagine planting a few posts at the corners of a field with a few dollars worth of radio equipment each, and getting higher resolution without relying on satellite.
Reading other comments here, it seems that these exist, in tandem with GPS, to get absolute positioning. But I don't see why absolute positioning would be needed; relative positioning should suffice.
I was thinking of component cost when I said a few dollars; of course a commercial product is going to sell for thousands. In the 60GHz band (IEEE 802.11ad), you can plausibly get down to ~.5cm resolution with cheap, COTS network gear.
The labor to make that work is going to be expensive, but yes you can do that. GPS with corrections is the cheap and easy way to ensure everything works and then you get back to the business of farming.
I think a more charitable read of OP is that you don’t need a satellite (or even GPS) to provide centimeter-accurate localization over a wide area. Spacebound systems are always going to have worse uptime and less resiliency than ground ones.
10's of millions of people are wandering around with absolutely no conception of where their food comes from, and whether there is anything they need to do to keep it that way.
Everything is already complex. The rubber in the tires, foundries for the metal in the tractor, machining tools and welding equipment, the processes and tools to develop insecticides, water infrastructure. Why is a far away radio a bridge too far? It already takes a nation to build tractors at scale.
So is getting that computer up into space, keeping it there, and running, and returning to service in the inevitable case of failover.
...All of which seems a little silly in comparison to setting up some solar powered, battery backuped wireless radios/beacons, and establishing a localized coordinate grid, no extraterrestrial equipment required.
Or is cutting out a tractors width of field around all beacons enough to render a farmer uncompetitive as well?
I just resent the implication that just because we have GPS satellites, that those are the only form factor such a solution can take. I always saw satellite GPS as A) a quick global win for the public and B) sort of an incentive to keep iterating on rocketry in parallel with establishing similar terrestrial nav gridding.
I don't think it is wise to just not establish terrestrial nav grids because GPS. Always, always, always build redundancies.
It's just that land isn't a flat 2D plain, and plots aren't quadrangles. It's more complicated than driving stakes into the ground at the corners. Then there's the matter of the ground shifting and weather affecting the beacons. I agree that redundancy is good, but if terrestrial nav grids with ~4cm resolution were operationally easy we wouldn't be having this conversation.
In the unlikely event any Aussie or NZ farmers are reading this, it costs less than $1k to setup your own base station and transmit corrections via a number of RF links. One base station is good to a radius of about 60km, so not enough for large ranches but fine for crops. You can setup as many as you need, then no reliance on L band SBAS
"SouthPAN services in Australia and New Zealand are back online and available to users, as the service outage affecting SouthPAN users via Inmarsat I-4F1 Satellite has now been rectified."
As a keen OpenStreetmapper I'm always interested in improvement to accuracy. However its a two edge sword as I found out when I got a L1/L5 mouse receiver. A whole bunch of street centrelines locally are out by 1-2m which is seriously annoying when you know about it.
As others mentioned this sounds unrelated to GPS. Have any colleges been working on a local and self hosted server / transceiver to control tractors and remove this single point of success? Maybe even take GPS out of the equation by having perimeter or fence-line beacons to create a virtual map for the tractor? Bonus if someone made a kit to retrofit old tractors. I could have some fun with my 1947 Fordson 2N driving itself.
I can't imagine relying on private SBAS when DIY RTK is so cheap and easy now. Sparkfun will set you up with your own base station hardware for under $1000, I wonder what a year of inmarsat corrections costs.
Historically (perhaps prices have come down a lot in the last decade with the introduction of the L5 signal?) getting RTK corrections from a third party meant you only needed one $20,000 receiver, instead of two.
Yeah, um, I have a base+rover pair, with the base set up in my kitchen window and the rover on my quadcopter, for around $600 total... no internet required, no corrections source, all the math done inside the F9P itself by default, or offboard with rtklib if I'm feeling masochistic...
The article is from two days ago. Here's another article saying the satellite is at least partially back online? I don't know if that helps farmers, though.
> Inmarsat’s aircraft safety and other L-band satcom services for the Asia-Pacific region are operable again, following an outage of the firm’s I-4 F1 satellite which forced operators to switch to high frequency (HF) radio. The news comes as a relief to operators, pilots, aviation enthusiasts and tech-savvy flyers.
> London-based Inmarsat explains in a fresh update today that the L-band satellite “suffered a partial loss of power” which invoked automatic procedures on the satellite that led to the suspension of services for East Asia and the Pacific region starting at 21.14 UTC on Sunday 16 April.
> The British satellite Inmarsat I-4 F1, which provides services for East Asia and the Pacific regions, is back in operation after an outage on Sunday.
> The incident is prompting farmers and industry groups to examine their backup systems for the technology they are using.
Ive been working with GNSS for the last decade and a bit, and this article and the comments here are a low point for HN in terms of people making comments about stuff they dont understand.
PSA: if you want to learn about corrected GNSS, stop reading this thread now. I started replying to some comments then gave up, most here are more wrong than right.
This place selects for confident contrarian takes based on superficial knowledge.
I get really annoyed by how in nearly any physics or cosmology post, half the comments are a bunch of people smugly declaring that dark matter is just an imaginary fudge factor added by lazy dishonest scientists.
Get a ublox F9P board and antenna. Couple hundred dollars.
Set it up to do RTK using public CORS base stations (will give you 2cm apx accuracy). You will get a kick out of it.
Then next level is grab the latest rtklib, and do PPP processing.
The RTK step is simple and will boost your motivation to learn more. PPP is also easy to setup, but there are many things you can take to make it more accurate. Each one you will learn about something new. Satellite clock corrections, position corrections, ionosphere and troposphere modelling, receiver dynamics, tidal loading, wind up, etc. List goes on a lot
Once you've done that you'll have a 'feel' for it. From there you'll find your own resources based on what most interests you
And yea, it is fascinating. I'm not bored of it after all this time. New stuff keeps coming out. SSR is super interesting right now
This seems like a great use for having a differential RTK GPS receiver at a known good location at the edge of a property. Once it's set up, the moving receiver can use the stationary receiver as a source of correction instead of relying on SBAS or WAAS.
So long as the known location GPS has power, hasn't been hit by lightening, hasn't be stolen by local kids, and the radio signal can reach your GPS (this is a big one - some farmers do this, but they have one GPS at home and sometimes it cannot reach all the fields), or any other the other things that can go wrong.
"Grind to a halt" is an awful overstatement here. They should really be saying "farmers lose 4% efficiency boost from downed GPS system" instead.
I worry there's a serious misconception in the discussion of this article on the current utility of these GPS systems. It's not like Interstellar, where farm equipment can run unattended--you still need a worker in the tractor to perform the turns at each corner and monitor any deficiencies in the seeder/sprayer. I grew up on a farm growing the crops listed in this article. We didn't get GPS guidance on any of our tractors until the early 2010's--GPS is a convenience, not a dependency. If GPS systems were malfunctioning, we would revert to the way we had planted for decades: drive in a straight line towards the next n'th fence post over at each turn.
It's terrifying to think what could happen with a mass coronal ejection or some other catastrophic event. When you see events like this and the Ever Given incident.
We've built a very complex distributed system that lacks resiliency in some very serious ways.
Driving the tractors is pretty far down on the things to worry about if a CME happens where every electrical grid on the planet would be down for months
Nitpicking maybe but in the event described, a lot of people would need to start doing things they’ve never done before, like driving super large tractors ?
I'm a little too lazy to read the article (I'm not super interested, and I'm sure experts are solving the problem as we speak) but I'm curious about "gentle degradation" or "fail-safe" modes: If the satellite/location correction data is not available, does the positioning just get worse by (I think I read) 4%, or did they not anticipate this type of failure and the equipment is actually stuck and useless?
The tractor can always be driven by hand. Tractors have not literally "ground to a halt".
The systems that have failed are those using GPS with differential corrections, which achieve ~2cm accuracy for 'precision agriculture' (tractor auto-steer, making efficient use of chemicals by only spraying them precisely on the plant, etc)
The degradation is they now only have normal GPS which is accurate to within a few meters - but that's useless for precision agriculture.
It's kind of surprising that single satellites can still be so crucial, given that we have at least three operational navigation systems which phones can easily use (GPS, GLONASS, BeiDou and Galileo). Are those not all truly global?
This is a navigation satellite, it is a communication satellite that sends information you cannot get via GPS. The speed of light in the atmosphere is not a constant, this satellite is sending corrections so you can account for that (that is there is some other GPS 'near' you, at a known location, and then it compares where GPS says it is to where it really is and you subtract that difference).
While these may be truly global, I don't know that all "GPS" satellites are. They reference a specific brand of satellites. Their website mentions that this satellite only services the asian pacific region.
Seems like GPS is a bad fit for this problem, really. Farm fields are flat. Put up some flashing lights in the corners of a field and use cameras to find them and adjust your position. Done.
You can put devices in the field that substitute for the GPS satellites. But you have to know where the device is! So it'd have to have been installed before the outage.
That used to be done. They're called "psuedolites". You'd put one somewhere on your property. It listens to the GPS satellites, and over a few hours, gets its own location very accurately by averaging error. Then it rebroadcasts a correction signal to cooperating GPS receivers nearby. Some airports have used these. They're called "ground based augmentation systems" in aviation.
There are agricultural versions. Deere sells some.[1] They call this "RTK".
Would it not be possible to do a DIY with a collection of mapped stationary transmitters? It's not like it needs to learn about anything outside the farm in question.
It amazes me that we’ve been able to fine tune optimal agricultural practices to the point the a GPS system is a key tool in precision & optimized land usage.
This article doesn’t make sense because Inmarsat-41 is not a GPS satellite, so the farm equipment must have been relying on it for something other than “their GPS signal”. It would be nice to know what that something was, so that similar single points of failure can be avoided in the future.
