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Super-Accurate GPS Chips Coming to Smartphones in 2018

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Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#161

Post by unholiness »

phkahler wrote: post #136

Accuracy vs Precision. So they can pin your position to within 30 centimeters, but how small of changes can be detected? Can they detect relative movement on the order of 1cm or less? that would be really useful for some things. For example if you wanted to measure the distance between 2 points on the ground, you don't care about offsets but do care about precision.

You mean absolute vs. relative measurement. Accuracy vs. precision is a different concept.

It is possible that a setup with high-precision absolute measurements can produce high-accuracy relative measurements, but the former does not imply the latter (imagine, for instance, any source of error in absolute measurements that's locally non-linear).

Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#162

Post by hammock »

hammock wrote: post #129
chii wrote: post #55

Earlier quoted context omitted.

is there any reason to be even more accurate than a 5 meter radius? I mean, if you are targeting a person in a building, i can't see why it has to be more accurate than that. Navigation of a drone that is less than 5 meters in size may require higher accuracy, i suppose...

Wow really? You would post that on a technology board? Yesterday I read an idea from a guy who wanted to create a mariokart-style "ghost" via AR to pace you while you are on a run. That's one example.

Guess I'm being downvoted for snark. But the definition of technology is to advance the state of the art. None of us would be here if we thought everything was already good enough.

Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#164

Post by jronsomers »

skummetmaelk wrote: post #56
microcolonel wrote: post #22

Earlier quoted context omitted.

For what it's worth, all operators have a legal obligation to gather these data (at least in the U.S. and Canada) officially for emergency services purposes.

"Emergency services"

Those emergency services are very convenient when it comes to flood warnings, tornado warnings, and even amber alerts. I am personally very glad to have them.

Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#165

Post by jtolmar »

cantagi wrote: post #84
jtolmar wrote: post #69

Earlier quoted context omitted.

I've been working on GPS filtering for three years and that's bad even by my standards. Chips with L5 should do a lot to clear that up though.

I have a question for you. If GPS locations in cities are affected by reflections off buildings, wouldn't the effect be deterministic and could you take advantage of that to reduce the noise?

It's deterministic, but changes multiple times per city block, so it's hard to build a model that accurately does something about it.

Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#166

Post by Qworg »

abakker wrote: post #157
ac29 wrote: post #149

Earlier quoted context omitted.

>Can they detect relative movement on the order of 1cm or less? The short answer is no, largely due to localised ionospheric conditions. The longer answer is yes, GNSS systems can be enhanced in accuracy using RTK [0][1]. This allows for precision on the order of 1cm, but requires a (rather expensive) fixed position base station to provide corrections. Surveyors, precision ag, and other large machine control (think d…

I think RTK can now be done from fixed base stations over data network, so is it possible it could be implemented on devices like this?

Definitely! It is just more chips and you need to be "close" to a fixed station.

Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#167

Post by Skunkleton »

katastic wrote: post #62
MertsA wrote: post #45

Earlier quoted context omitted.

>The military has better precision, only because they buy better hardware. That's not true. Military receivers can use the Y Code which is encrypted for military use only. There are some really fancy civilian receivers out there that can leverage Y code to a limited extent without knowing the encryption key but full accuracy is only possible on a military receiver that can decrypt and use the Y code.

Don't you mean... M-code? (meaning "military" code) https://en.wikipedia.org/wiki/GPS_signals#Military_.28M-code... Though I'm honestly surprised I've "known" of GPS for this long and never realized there were a variety of codes. Legacy--some still operating, modern, military, and more. I'm going to enjoy binge reading this wiki/math stuff tomorrow.

m-code is the new hotness that is stuck in development hell currently.

Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#168

Post by ac29 »

abakker wrote: post #157
ac29 wrote: post #149

Earlier quoted context omitted.

>Can they detect relative movement on the order of 1cm or less? The short answer is no, largely due to localised ionospheric conditions. The longer answer is yes, GNSS systems can be enhanced in accuracy using RTK [0][1]. This allows for precision on the order of 1cm, but requires a (rather expensive) fixed position base station to provide corrections. Surveyors, precision ag, and other large machine control (think d…

I think RTK can now be done from fixed base stations over data network, so is it possible it could be implemented on devices like this?

I don't know quite enough about the technical details to be sure, but RTK can defintiely go over IP networks with NTRIP and other protocols. The biggest limitation with RTK is that the corrections are limited to 10-15 miles of the base/reference station (more is possible, generally with less accuracy), since ionospheric conditions vary enough to make the corrections highly location dependant.

The antenna systems on RTK rovers (the devices receiving corrections, which also receive the GPS satellite signals) aren't huge, but I'm not sure if they could be reduced in size enough to fit in a smartphone.

Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#169

Post by grandalf »

ac29 wrote: post #150
Animats wrote: post #44

15cm GPS accuracy has been available commercially since about 2002. Trimble and Novatel both sold units. But you had to get a subscription to a service which had a network of ground stations measuring propagation errors through the atmosphere. The correction signals came in from a geosync satellite. You also had to be able to see about five satellites.

~1cm accuracy is available now from dozens of companies, and doesn't require a subscription (though subscription services are still available).

link(s)?

Re: Super-Accurate GPS Chips Coming to Smartphones in 2018

#170

Post by ac29 »

grandalf wrote: post #169
ac29 wrote: post #150

Earlier quoted context omitted.

~1cm accuracy is available now from dozens of companies, and doesn't require a subscription (though subscription services are still available).

link(s)?

Leica Geosystems [0], Topcon Positioning Systems [1], and Trimble [2] are the companies I deal with most often, but there are many, many others.

[0] http://leica-geosystems.com/en-us

[1] https://www.topconpositioning.com/

[2] http://www.trimble.com/

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