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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

#141

Post by maxerickson »

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'd already probably use a a tape or laser if you were measuring a distance short enough for centimeters to matter.

(100 meters isn't that far; 1 cm at that range is already 1/10000 of the distance; Commercial equipment can apparently do millimeters across kilometers: http://www.micro-epsilon.com/displacement-position-sensors/l... )

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

#142

Post by bb611 »

coderjames wrote: post #119
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...

Airplanes are already using the higher-accuracy GPS+GNSS to land safely on the runway in low-visibility conditions, guided in by the Flight Management Computer. It makes a big difference whether the plane is 5 meters above the runway or zero meters above the runway.

Commercial airliners use a radar altimeter, not GPS/GNSS to assess altitude.

Most if not all airliners equipped with autoland systems use ILS rather than GPS for position as well.

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

#143

Post by eeZah7Ux »

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.

I had to look it up: https://en.wikipedia.org/wiki/Accuracy_and_precision

...and I'm surprised by the silly choice of words in English: it's really confusing.

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

#144

Post by LeifCarrotson »

eeZah7Ux wrote: post #143
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.

I had to look it up: https://en.wikipedia.org/wiki/Accuracy_and_precision ...and I'm surprised by the silly choice of words in English: it's really confusing.

It's quite normal for words which might seem to have the same meaning in the common vernacular to have nuanced meanings within a domain. This doesn't just apply to science and engineering - consider law, medicine, religion, food service...really just about anything you can think of. And it's not just an English language phenomenon, either: two words that mean the same (exact, identical, similar) thing really implies there's a difference between the words.

And yeah, as a test engineer, metrology can be confusing, but that's because it's necessarily complex, not because of silly choices.

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

#145

Post by Crosseye_Jack »

24gttghh wrote: post #140
deckar01 wrote: post #10

Earlier quoted context omitted.

Things have changed since the 90s. > In May 2000, at the direction of President Bill Clinton, the U.S. government ended its use of Selective Availability in order to make GPS more responsive to civil and commercial users worldwide. > The United States has no intent to ever use Selective Availability again. The military has better precision, only because they buy better hardware. Similar hardware is used in commercial…

Is there not still a limit to GPS accuracy when civilian receivers go beyond a certain speed? e.g. to deter clandestine missile development?

iirc the requirements are an AND condition for speed and altitude. >1,000 knots AND >18,000m. But many civilian receivers implement it as an OR condition much to the annoyance of the near space balloon community.

Some will even switch of the radio once one of these limits are reached and not enable it until it's been reset so make them a pain to use for even if you just wanted the location data after your payload comes back down within the limits.

EDIT: But yeah the so-called COCOM limits still apply to civilian equipment (esp to a company such as Broadcom). Unsure on the regulations for modifying the firmware on a device that doesn't put these lockouts at the silicon layer. For example: https://github.com/swift-nav/libswiftnav/blob/master/src/pvt...

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

#146

Post by X-Istence »

sgk284 wrote: post #8
gruez wrote: post #4

>will give the next generation of smartphones 30-centimeter accuracy instead of today’s 5-meters Didn't the US scramble the civilian signals specifically so it wouldn't be too accurate? And they're just okay with civilians having access to ultra accurate GPS receivers?

There's usually restrictions that kick in at certain altitudes and/or hardware restrictions if you're going over a certain speed. Depending on the source of signals used, the military can also just change the precision for civilian bands. But in times of peace / low threat levels, there's not a particular need to do so.

This should be an "and", unfortunately many GPS receivers consider it an "or".

Makes them worthless for high altitude near space balloons :-(

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

#147

Post by z2 »

antonioalegria wrote: post #102

How does this compare with iPhone 8/X, which supports the Galileo system, as well as GPS and GLONASS?

As said, the value here is the dual-frequency support. However, the features listed on Broadcom's site [1] show:

  The BCM47755 can simultaneously receive the following signals:
    GPS L1 C/A
    GLONASS L1
    BeiDou (BDS) B1
    QZSS L1
    Galileo (GAL) E1
    GPS L5
    Galileo E5a
    QZSS L5
[1] https://www.broadcom.com/products/wireless/gnss-gps-socs/bcm...

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

#148

Post by QAPereo »

LeifCarrotson wrote: post #144
eeZah7Ux wrote: post #143

Earlier quoted context omitted.

I had to look it up: https://en.wikipedia.org/wiki/Accuracy_and_precision ...and I'm surprised by the silly choice of words in English: it's really confusing.

It's quite normal for words which might seem to have the same meaning in the common vernacular to have nuanced meanings within a domain. This doesn't just apply to science and engineering - consider law, medicine, religion, food service...really just about anything you can think of. And it's not just an English language phenomenon, either: two words that mean the same (exact, identical, similar) thing really implies…

“Terms of Art” is the go to descriptor for that kind of thing in law.

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

#149

Post by ac29 »

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.

>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 dozers, graders, etc) have used this technique for precision positioning for the past decade or so.

I do recall reading that upcoming GPS satellites add a second civilian frequency, which I believe will enable these sort of ionospheric corrections to be done more easily and inexpensively.

[0] http://www.navipedia.net/index.php/RTK_Fundamentals

[1] https://en.wikipedia.org/wiki/Real_Time_Kinematic

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

#150

Post by ac29 »

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).
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