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Making regular GPS ultra-precise

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Re: Making regular GPS ultra-precise

#51

Post by adgjlsfhk1 »

_flux wrote: post #41
eqvinox wrote: post #13

Earlier quoted context omitted.

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'…

Are there modern cheap IMUs that are able to hold position for some time available? My understanding is that using plain accelerometers and gyros will drift quite soon due to noise, while some cars (e.g. Tesla) maintain their position quite well when doing to an underground parking structure and then coming back. So I actually do believe that they put a lot of weight to tracking wheels, which I believe would not accu…

yeah Phones have pretty good IMUs. the TLDR is you combine accelerometers and gyros (preferably a bunch of them to minimize error) with GPS which gives you pretty accurate position and can also give you velocity data with some tricks)

Re: Making regular GPS ultra-precise

#52

Post by BenjiWiebe »

myself248 wrote: post #11
Havoc wrote: post #3

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 fr…

Advertising and discovery: rtk2go.com or similar. Public casters.

Re: Making regular GPS ultra-precise

#54

Post by jlack »

tecleandor wrote: post #18
eqvinox wrote: post #6

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?

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 thoug…

Extra satellites only have the potential to help a little bit in urban environments by increasing the odds of having a satellite directly overhead. Dense urban environments will have high multipath(longer time for signal to get to the receiver due to bouncing off buildings) which causes the position to be inaccurate.

Re: Making regular GPS ultra-precise

#55

Post by _flux »

adgjlsfhk1 wrote: post #51
_flux wrote: post #41

Earlier quoted context omitted.

Are there modern cheap IMUs that are able to hold position for some time available? My understanding is that using plain accelerometers and gyros will drift quite soon due to noise, while some cars (e.g. Tesla) maintain their position quite well when doing to an underground parking structure and then coming back. So I actually do believe that they put a lot of weight to tracking wheels, which I believe would not accu…

yeah Phones have pretty good IMUs. the TLDR is you combine accelerometers and gyros (preferably a bunch of them to minimize error) with GPS which gives you pretty accurate position and can also give you velocity data with some tricks)

But if you don't have GPS, then you don't have a high-confidence low-precision absolute position input to your system? Whereas with wheels you already get a lot of data about that when they are not turning at all.

A friend tried to make a phone ruler app (using IMU) and the experience was that it didn't take very long for the distance to shoot to the horizon. So, thought I should try how this kind of solution would work with the hardware of today, but it turns out there seem to be zero such apps in the Play Store.. The tools of that category all seem to use a camera.

I think the lack of these tools is a testament to the approach not really working.

Re: Making regular GPS ultra-precise

#56

Post by cyanydeez »

LeifCarrotson wrote: post #32
bluGill wrote: post #23

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 up…

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 a…

The likely cause of this is the depersonalization of people at the behest of technology.

Re: Making regular GPS ultra-precise

#57

Post by cyanydeez »

eqvinox wrote: post #6

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?

It ready mostly like an advertisement for Google's API.

Re: Making regular GPS ultra-precise

#58

Post by cyanydeez »

jlack wrote: post #54
tecleandor wrote: post #18

Earlier quoted context omitted.

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 thoug…

Extra satellites only have the potential to help a little bit in urban environments by increasing the odds of having a satellite directly overhead. Dense urban environments will have high multipath(longer time for signal to get to the receiver due to bouncing off buildings) which causes the position to be inaccurate.

They hand waved over a lot of it. The improvements in the urban canyon are not coming from GPS, but from things like wifi and 3d mapping, probably including cellular triangulations.

Re: Making regular GPS ultra-precise

#59

Post by cyanydeez »

crote wrote: post #20
Havoc wrote: post #3

Why don’t cities have ground beacons for this? Much cheaper than satellites and would be guaranteed to see heavy use

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.

no, you arn't understanding. Those beacons would just be fixed places that know what their position is according to the GPS network.

You're tihnking of someone tkaing a GPS sattilite and putting it somewhere.

Re: Making regular GPS ultra-precise

#60

Post by andrepd »

bluGill wrote: post #23

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 up…

The things people do to avoid building trains and cycle paths.
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