Precision GPS is useful for a lot of things, but not for safety. Until we equip every deer, child, and pavement heave with a GPS saying exactly where it is cars will need "something" else to detect hazards. That GPS needs to be 100% reliable, even though we cannot predict when a child will attempt to run outside naked (without their GPS position transmitter), or the pavement will decide to fail (presumably without updating the GPS).
Prevision GPS is useful for a lot of things, but it isn't needed for car navigation. If you know within 100 meters of where you are you can figure out the exact lane you are in by other clues - clues that you need to look for anyway because road/utility crews will sometimes direct you to do things that are not on your updated maps.
I couldn't read the rest of the article because that navigation bugged me too much.
If/when QPS is realized, calibration to a fixed point via manual verification, fixed base station(s), and/or multiple GNSS systems then GNSS spoofing, accuracy, and precision won't matter all that much because it will be entirely self-contained.
It's absurd overkill to put GNSS transmitters, RFID tags, and/or Bluetooth beacons on every object because the world is being flooded, for better or worse, with AI visual and IR cameras.
> Prevision GPS is useful for a lot of things, but it isn't needed for car navigation. If you know within 100 meters of where you are you can figure out the exact lane you are in by other clues - clues that you need to look for anyway because road/utility crews will sometimes direct you to do things that are not on your updated maps.
Except it is because driving direction routing depends on determination is based upon knowing which of several parallel, different roads one is on like the difference between being on a highway and on a parallel frontage road. Incorrect road detection leads to offering wrong directions.
The social norm that we seem to be slowly stumbling into assumes a different state of affairs:
That the roadways ought to always be clear of anything but cars which are behaving normally, and that if you can keep a car in the lane then anything unusual which happens isn't the car driver's fault.
Debris, animals, children, pedestrians, cyclists, motorcycles, stopped cars, construction workers and their vehicles, and anything else in our complex world that may find its way into the road - these aren't visible to someone blinded by oncoming headlights at night, they don't register in the same way as a car in the peripheral vision of someone looking at their cell phone or touchscreen controls, they may not be detected by radar cruise sensors or lane centering cameras, they certainly won't register on a GPS navigation track...and in a collision, society increasingly blames the thing that wasn't ~~supposed to be there~~ *anticipated* to be there rather than the driver which crashed into the thing.
I recognize that the likely cause of this is simply the infrequency of those events. Spend a few thousand miles seeing little other than cars on the road, and it's easier for your brain to assume that cars are the only thing that can be on the road. But my skeptical, cynical, conspiracy-minded side wonders if some of this trend is encouraged by submarine marketing efforts from self-driving vendors - the problem gets a lot easier when your "autonomous" vehicle isn't at fault for hitting a pedestrian in the road and you can just follow a GPS track while sensing for 5000 lbs steel boxes following the same GPS track.
Nothing in this article is new, and the problem with RTK has always been the (unpaid) availability of reference stations. Good on them for trying to make a package of it, but maybe this "news" site could've used a bit less unchecked enthusiasm.
Also, RTK is the opposite of "regular" GPS, it's generally considered a "special" usage mode of GPS.
And discussing urban canyons with no mention of QZSS?
> The Quasi-Zenith Satellite System (QZSS) (Japanese: 準天頂衛星システム, Hepburn: juntenchō eisei shisutemu), also known as Michibiki (みちびき, "guidance"), is a regional navigation satellite system (RNSS) and a satellite-based augmentation system (SBAS) developed by the Japanese government to enhance the United States-operated Global Positioning System (GPS) in the Asia-Oceania regions, with a focus on Japan.
Fun thing (?), I was excited on my last trip to Japan so I could test QZSS with my Pixel 9a, that supports it, and my GPS experience in urban canyons, specially in Shibuya, was terribly bad.
Even when in GPS Test or GPS Lock tools it was showing better than 3 meter horizontal accuracy, and a multitude of locked satellites, including some QZSS, the location would usually be 30 to 50 meters away. The first days I though I had lost all my capacity to navigate Tokyo, then I noticed the GPS was gas-lightning me.
I tried removing the phone case, changing GPS settings... and I had no luck.
Even back in 1999 prior to Selective Availability (SA) zeroing[0], fixed base station-assisted (pre-WAAS DGPS RTK) could achieve 10 mm horizontal accuracy and 1 m vertical accuracy. It was good enough that farming, mining (above ground), and earth-moving equipment could combine 2 receivers to determine tool angle and cut depth.
0. SA was an injected random error for security reasons that was constant for a local area, so it was weak security because it could be easily defeated if a fixed base station's position was known by subtracting it in the RTK receiver via DGPS update.
Some places have free RTK networks their citizens can use. Michigan's department of transportation, for instance, runs a CORS network that anyone can request access to. (At least as far as I can tell. The signup form doesn't ask for affiliation or payment.) It's just distributed over the internet, the assumption being that you probably have internet access already.
One of these days I'll figure out how to set up a free NTRIP caster on my Galmon station so it can do double-duty. The trick then is advertising and discovery.
It would be lovely to have, say, a standard wifi SSID or a standard LORA channel that your local corrections network would broadcast on. That way you could have a large number of client devices not each needing their own internet access SIM card or whatever. I wonder if the corrections stream would fit into an FM RDS payload or something.
Trouble is, there's so much money in the L-band corrections services, and so little money in replacing them for free...
Oh, yeah, the cryptocurrency folks have weighed in, there's a thing called "goodnet" which appears to be microtransactions in exchange for NTRIP streams over some medium. I haven't looked further into it.
>1 cm accuracy is also possible with a few lower cost receivers (such as the NEO-M8T) by capturing raw streams from the GPS satellites and then post processing the logs with an open source program called RTKLIB.
GPS beacons would be stupidly expensive, as you'd need tens of thousands of them per city, and each one of them would need a very accurate atomic clock.
It would make far more sense (but still unviable) to go for Eurobalise-style RFID tags embedded in the road surface.
That's kinda what RTK does, you have a ground station and transfer correction data for the visible satellites from it to your GNSS receiver. It doesn't transmit a GNSS signal itself but functionally the effect is vaguely comparable to a "satellite on the ground", without interfering on the actual signals.
Another option to get more precise positioning is to switch from GPS to Galileo.
Galileo generally offers better civilian accuracy than GPS because it uses modern signal structures with better resistance to multipath and interference and provides dual-frequency signals (E1 + E5) to all users, which mitigates ionospheric errors.
Almost, they use accelerometers and gyros, 'dead reckoning' is the keyword to look for. The wheels are a bit unreliable because the diameter changes slightly with pressure and temperature.
The legal requirements on that (in most places) are that the speedometer is in something like a -0%/+10% range, i.e. never shows lower than you're actually driving. Not only is that not helpful for navigation (but you could compensate that/shift the error window), but the precision is also pretty low (which you can't easily compensate).
(There are two precision problems here — tyre diameter changes slighly while you're driving, but also it's not precise to begin with before you even turn on the car, due to tyre wear.)
You'd need to do something like calibrating wheel speed data while you have good GNSS reception, then you could use it for dead reckoning. But accelerometers and gyros are cheap…
P.S.: I didn't say wheel speed data isn't used, just that it wouldn't be precise enough on its own.
Yup! Otherwise your navigation would become totally useless the second you entered a tunnel.
Dead reckoning can get quite accurate once you realise that cars drive on roads, so if you have a reasonably up-to-date map you can use turns and corners to "snap" back to the road and reset a good bunch of your accumulated error.
Precision GPS is useful for a lot of things, but not for safety. Until we equip every deer, child, and pavement heave with a GPS saying exactly where it is cars will need "something" else to detect hazards. That GPS needs to be 100% reliable, even though we cannot predict when a child will attempt to run outside naked (without their GPS position transmitter), or the pavement will decide to fail (presumably without updating the GPS).
Prevision GPS is useful for a lot of things, but it isn't needed for car navigation. If you know within 100 meters of where you are you can figure out the exact lane you are in by other clues - clues that you need to look for anyway because road/utility crews will sometimes direct you to do things that are not on your updated maps.
I couldn't read the rest of the article because that navigation bugged me too much.
If/when QPS is realized, calibration to a fixed point via manual verification, fixed base station(s), and/or multiple GNSS systems then GNSS spoofing, accuracy, and precision won't matter all that much because it will be entirely self-contained.
It's absurd overkill to put GNSS transmitters, RFID tags, and/or Bluetooth beacons on every object because the world is being flooded, for better or worse, with AI visual and IR cameras.
> Prevision GPS is useful for a lot of things, but it isn't needed for car navigation. If you know within 100 meters of where you are you can figure out the exact lane you are in by other clues - clues that you need to look for anyway because road/utility crews will sometimes direct you to do things that are not on your updated maps.
Except it is because driving direction routing depends on determination is based upon knowing which of several parallel, different roads one is on like the difference between being on a highway and on a parallel frontage road. Incorrect road detection leads to offering wrong directions.
The social norm that we seem to be slowly stumbling into assumes a different state of affairs:
That the roadways ought to always be clear of anything but cars which are behaving normally, and that if you can keep a car in the lane then anything unusual which happens isn't the car driver's fault.
Debris, animals, children, pedestrians, cyclists, motorcycles, stopped cars, construction workers and their vehicles, and anything else in our complex world that may find its way into the road - these aren't visible to someone blinded by oncoming headlights at night, they don't register in the same way as a car in the peripheral vision of someone looking at their cell phone or touchscreen controls, they may not be detected by radar cruise sensors or lane centering cameras, they certainly won't register on a GPS navigation track...and in a collision, society increasingly blames the thing that wasn't ~~supposed to be there~~ *anticipated* to be there rather than the driver which crashed into the thing.
I recognize that the likely cause of this is simply the infrequency of those events. Spend a few thousand miles seeing little other than cars on the road, and it's easier for your brain to assume that cars are the only thing that can be on the road. But my skeptical, cynical, conspiracy-minded side wonders if some of this trend is encouraged by submarine marketing efforts from self-driving vendors - the problem gets a lot easier when your "autonomous" vehicle isn't at fault for hitting a pedestrian in the road and you can just follow a GPS track while sensing for 5000 lbs steel boxes following the same GPS track.
Nothing in this article is new, and the problem with RTK has always been the (unpaid) availability of reference stations. Good on them for trying to make a package of it, but maybe this "news" site could've used a bit less unchecked enthusiasm.
Also, RTK is the opposite of "regular" GPS, it's generally considered a "special" usage mode of GPS.
And discussing urban canyons with no mention of QZSS?
> The Quasi-Zenith Satellite System (QZSS) (Japanese: 準天頂衛星システム, Hepburn: juntenchō eisei shisutemu), also known as Michibiki (みちびき, "guidance"), is a regional navigation satellite system (RNSS) and a satellite-based augmentation system (SBAS) developed by the Japanese government to enhance the United States-operated Global Positioning System (GPS) in the Asia-Oceania regions, with a focus on Japan.
https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System
Fun thing (?), I was excited on my last trip to Japan so I could test QZSS with my Pixel 9a, that supports it, and my GPS experience in urban canyons, specially in Shibuya, was terribly bad.
Even when in GPS Test or GPS Lock tools it was showing better than 3 meter horizontal accuracy, and a multitude of locked satellites, including some QZSS, the location would usually be 30 to 50 meters away. The first days I though I had lost all my capacity to navigate Tokyo, then I noticed the GPS was gas-lightning me.
I tried removing the phone case, changing GPS settings... and I had no luck.
There is decent RTK coverage in the US these days: https://e38surveysolutions.com/pages/ntrip-rtk-network-acces...
RTK = Trimble Navigation.
Even back in 1999 prior to Selective Availability (SA) zeroing[0], fixed base station-assisted (pre-WAAS DGPS RTK) could achieve 10 mm horizontal accuracy and 1 m vertical accuracy. It was good enough that farming, mining (above ground), and earth-moving equipment could combine 2 receivers to determine tool angle and cut depth.
0. SA was an injected random error for security reasons that was constant for a local area, so it was weak security because it could be easily defeated if a fixed base station's position was known by subtracting it in the RTK receiver via DGPS update.
Why don’t cities have ground beacons for this?
Much cheaper than satellites and would be guaranteed to see heavy use
Some places have free RTK networks their citizens can use. Michigan's department of transportation, for instance, runs a CORS network that anyone can request access to. (At least as far as I can tell. The signup form doesn't ask for affiliation or payment.) It's just distributed over the internet, the assumption being that you probably have internet access already.
One of these days I'll figure out how to set up a free NTRIP caster on my Galmon station so it can do double-duty. The trick then is advertising and discovery.
It would be lovely to have, say, a standard wifi SSID or a standard LORA channel that your local corrections network would broadcast on. That way you could have a large number of client devices not each needing their own internet access SIM card or whatever. I wonder if the corrections stream would fit into an FM RDS payload or something.
Trouble is, there's so much money in the L-band corrections services, and so little money in replacing them for free...
Oh, yeah, the cryptocurrency folks have weighed in, there's a thing called "goodnet" which appears to be microtransactions in exchange for NTRIP streams over some medium. I haven't looked further into it.
Thanks - that's a lot of good info :)
Sparkfun page suggests one can do some of these adjustments via software too:
https://learn.sparkfun.com/tutorials/what-is-gps-rtk/all
>1 cm accuracy is also possible with a few lower cost receivers (such as the NEO-M8T) by capturing raw streams from the GPS satellites and then post processing the logs with an open source program called RTKLIB.
Post-processing is wild. Lots of detail here: https://rtkexplorer.com/
There are even cheaper raw-data receivers, this one is popular among Galmon stations: https://www.aliexpress.us/item/2251832630341954.html
While we're at it, could we also broadcast navigation map updates via that FM stream?
Do you mean GEODNET?
Oops, indeed I do.
The newest TV broadcast standard (ATSC 3.0) does include positioning information which is far, far, far harder to jam than GPS signals.
https://www.nab.org/bps/
GPS beacons would be stupidly expensive, as you'd need tens of thousands of them per city, and each one of them would need a very accurate atomic clock.
It would make far more sense (but still unviable) to go for Eurobalise-style RFID tags embedded in the road surface.
https://en.wikipedia.org/wiki/Eurobalise Cool.
That's kinda what RTK does, you have a ground station and transfer correction data for the visible satellites from it to your GNSS receiver. It doesn't transmit a GNSS signal itself but functionally the effect is vaguely comparable to a "satellite on the ground", without interfering on the actual signals.
Galileo HAS allows precision down to 30cm with enough integration time. Without additional external data.
For free.
Receivers slowly hitting the market now - a year ago this was only receivable by SDR-driven devices.
"with enough integration time" — the article is about live navigation, which generally can't afford that.
With SBAS 1-2m precision can be done easily in the US and EU. Most of the time enough for any navigational use.
Pretty much all GPS/Galileo receivers are able to receive and decode these overlays.
Another option to get more precise positioning is to switch from GPS to Galileo.
Galileo generally offers better civilian accuracy than GPS because it uses modern signal structures with better resistance to multipath and interference and provides dual-frequency signals (E1 + E5) to all users, which mitigates ionospheric errors.
most software now uses multiple GNSS at the same time?
Usually cheaper GPS modules only do one band (L1), though. But using multiple constellations still helps a lot.
Yeah, according to the 'GPS Test' Android app my phone is picking up and using GNSS signals from GPS, Galileo, GLOSNAS, and Beidou sats.
Man I remember getting my first GPS receiver in the 90s and now are phones can use so many sats.
Don't cars also measure their wheel movements to increase location accuracy?
Almost, they use accelerometers and gyros, 'dead reckoning' is the keyword to look for. The wheels are a bit unreliable because the diameter changes slightly with pressure and temperature.
Wheels are still used for legal telemetry: speedometer and odometer.
The legal requirements on that (in most places) are that the speedometer is in something like a -0%/+10% range, i.e. never shows lower than you're actually driving. Not only is that not helpful for navigation (but you could compensate that/shift the error window), but the precision is also pretty low (which you can't easily compensate).
(There are two precision problems here — tyre diameter changes slighly while you're driving, but also it's not precise to begin with before you even turn on the car, due to tyre wear.)
You'd need to do something like calibrating wheel speed data while you have good GNSS reception, then you could use it for dead reckoning. But accelerometers and gyros are cheap…
P.S.: I didn't say wheel speed data isn't used, just that it wouldn't be precise enough on its own.
Yup! Otherwise your navigation would become totally useless the second you entered a tunnel.
Dead reckoning can get quite accurate once you realise that cars drive on roads, so if you have a reasonably up-to-date map you can use turns and corners to "snap" back to the road and reset a good bunch of your accumulated error.