IPhone 4S has GLONASS in addition to GPS • Hacker News Board

Re: IPhone 4S has GLONASS in addition to GPS

#61

Post by randomdata » Wed, Oct 19, 2011, 3:59 PM UTC

FrojoS wrote: post #46

nodata wrote: post #7

Earlier quoted context omitted.

They use this on automated farms. At known co-ordinates, they stick a GPS receiver in the ground. The difference between the known co-ordinates and what that GPS receiver sees is then continuously transmitted to the vehicles on the farm.

Thats very interesting. Do you have any information on how much these farms are automated?

Autosteer is quickly gaining in popularity. From looking at the farm equipment in my area, I'd guess that 40% have GPS systems on their tractors/combines based on observing the antennas on the equipment. Precision farming is becoming important to increasing yields and reducing costs.

Right now, Kinze are heavily touting their autonomous system for grain carts: http://www.youtube.com/watch?v=MhA5aIw7xNk

John Deere and CNH have similar systems in actual production, but still require an operator to be present for safety reasons. And safety seems to be the big limiting factor. While the technology is basically there, nobody wants to remove the operator just yet. Though in this video, someone disabled the safety sensors to go fully autonomous: http://www.youtube.com/watch?v=zU4liQvrcm4

Most farmers are pulling their RTK data over wireless/mobile internet connections, rather than having their own base station. I don't know of anyone who maintains their own station. A few companies have placed base stations around various places in the countryside and will happily sell you their data.

Re: IPhone 4S has GLONASS in addition to GPS

#62

Post by natch » Wed, Oct 19, 2011, 4:00 PM UTC

flipbrad wrote: post #15

dchest wrote: post #2

Precisions: * GPS: 2.00—8.76 m * GLONASS: 4.46—7.38 m * GPS+GLONASS: 2.37—4.65 m [citation needed] (source: http://en.wikipedia.org/wiki/GLONASS ).

I'm wondering whether it actually matters to people whether their GPS device has 2, 4 or 7m accuracy. Anything with lower resolution than about 5 cm is going to be largely useless for robotic driving, etc, particularly anything worse than 2 m res - so really (and not meaning to be rude to you and your research efforts) - isn't the different resolution irrelevant, and isn't the only reason GPS users should be happy ab…

I would love it if I could use "find my iPhone" inside my house without having to resort to the audible alert when other people are sleeping. So, yes, better resolution would be wonderful. Edit: and to address the obvious objection, no, the current resolution is not good enough for this. With the current accuracy, I'm not able to locate my phone within my house yet (iPhone 4, and no canyon issues here).

Re: IPhone 4S has GLONASS in addition to GPS

#63

Post by MrVitaliy » Wed, Oct 19, 2011, 4:06 PM UTC

mhw wrote: post #4

dchest wrote: post #2

Precisions: * GPS: 2.00—8.76 m * GLONASS: 4.46—7.38 m * GPS+GLONASS: 2.37—4.65 m [citation needed] (source: http://en.wikipedia.org/wiki/GLONASS ).

From which: To improve development of the user segment, on August 11, 2010, Sergei Ivanov announced a plan to introduce a 25% import duty on all GPS-capable devices, including mobile phones, unless they are compatible with GLONASS. I think I can see why the GPS chipsets are starting to adopt this...

That's hardly a motivation for Apple. They still don't have an official dealer in Russia and afaik don't have any plans. Yet, most of government officials widely use iPads (including the president) and every hip kid around the block has an iPhone. This suggests that Sergei Ivanov is merely looking for more ways to tax their own population, not Apple. Russian GLONASS is an archaic POS that they them selves have trouble working on their own, approved devices and a 25% import duty on GPS-capable devices won't fix it.

Re: IPhone 4S has GLONASS in addition to GPS

#64

Post by modeless » Wed, Oct 19, 2011, 4:16 PM UTC

mikepurvis wrote: post #8

nodata wrote: post #7

Earlier quoted context omitted.

They use this on automated farms. At known co-ordinates, they stick a GPS receiver in the ground. The difference between the known co-ordinates and what that GPS receiver sees is then continuously transmitted to the vehicles on the farm.

It's called rtk correction: http://en.wikipedia.org/wiki/Real_Time_Kinematic There's an opensource rtklib which supports a handful of inexpensive receivers: http://gpspp.sakura.ne.jp/rtklib/rtklib.htm

Why don't cell towers do this?

Re: IPhone 4S has GLONASS in addition to GPS

#65

Post by sjwright » Wed, Oct 19, 2011, 4:34 PM UTC

CWuestefeld wrote: post #54

lucaspiller wrote: post #21

Earlier quoted context omitted.

Also from the same page: Some modern receivers are able to use both GLONASS and GPS satellites together, providing greatly improved coverage in urban canyons and giving a very fast time to fix due to over 50 satellites being available. In indoor, urban canyon or mountainous areas, accuracy can be greatly improved over using GPS alone. Is there any reason, other than the higher number of sources, why GPS+GLONASS is be…

In situations like the "urban canyon", where the problem is that only a small slice of sky is visible, I would think that the advantages of using both systems would only be marginal. The most accurate GPS fix is had when the satellites you're seeing are widely separated in the sky. In the urban canyon, the problem isn't a lack of satellites, but the fact that you can only see those that happen to be in a narrow slice…

Yeah, but if there are more useful satellites in the sky, there's a greater chance of the visible satellites having a wider separation. Even in the 'urban canyon', you still frequently have partial sky visibility in some non-vertical directions. And there will be occasions when a GLONASS satellite will be better placed than a GPS satellite.

To use a reductio ad absurdum argument, imagine a satellite positioning network with a thousand nodes. Wouldn't it have a greater chance of providing a useful fix in this environment: http://g.co/maps/sa8zk ?

Re: IPhone 4S has GLONASS in addition to GPS

#66

Post by juiceandjuice » Wed, Oct 19, 2011, 4:43 PM UTC

singular wrote: post #51

eps wrote: post #13

Earlier quoted context omitted.

In mid 90s I worked for a company that developed combined GPS/GLONASS receiver and aimed specifically at high-precision measurement market. With clever math modeling and by letting a receiver rest on one spot for longer periods of time, e.g. 30 min, they could get the precision down to 3 mm (millimeters). And that's without A-GPS, purely through oversampling of satellite data.

It's funny you mention that, as I swear the professor said it could be done to accuracy of mm, but after reviewing the wikipedia articles I had concluded I misremembered. Perhaps not...

You can, but you need to need to analyze the phase of the GPS signals at the analog level (not the the code phase)

Re: IPhone 4S has GLONASS in addition to GPS

#67

Post by rtrunck » Wed, Oct 19, 2011, 4:46 PM UTC

zimpenfish wrote: post #3

I wonder if that's causing the odd jumping about I'm seeing on the 4S compared with the stable tracking of the 4.

I've been having significant jumps with my 4S compared to the 4 too. It seems like a regression in GPS quality so far.

Re: IPhone 4S has GLONASS in addition to GPS

#68

Post by rmoriz » Wed, Oct 19, 2011, 5:10 PM UTC

FrojoS wrote: post #46

nodata wrote: post #7

Earlier quoted context omitted.

They use this on automated farms. At known co-ordinates, they stick a GPS receiver in the ground. The difference between the known co-ordinates and what that GPS receiver sees is then continuously transmitted to the vehicles on the farm.

Thats very interesting. Do you have any information on how much these farms are automated?

maybe interesting:

In Europe (and of course in Germany) the federal governments offer realtime gps correction data via IP or 3G (radio was shut down a few years ago).

They offer a precision of 1cm-2cm used together with GPS/GLONASS

PDF: http://www.sapos.de/pdf/Flyer/2004Flyer_e.pdf

(Sorry, German language only:)

http://www.sapos.de/ http://sapos.bayern.de/service.php

Re: IPhone 4S has GLONASS in addition to GPS

#69

Post by HeyItsDiogenes » Wed, Oct 19, 2011, 5:22 PM UTC

modeless wrote: post #64

mikepurvis wrote: post #8

Earlier quoted context omitted.

It's called rtk correction: http://en.wikipedia.org/wiki/Real_Time_Kinematic There's an opensource rtklib which supports a handful of inexpensive receivers: http://gpspp.sakura.ne.jp/rtklib/rtklib.htm

Why don't cell towers do this?

Because cellular technology is actually designed to handle long distance with obstructions?

Re: IPhone 4S has GLONASS in addition to GPS

#70

Post by georgecmu » Wed, Oct 19, 2011, 5:26 PM UTC

Tloewald wrote: post #20

flipbrad wrote: post #15

Earlier quoted context omitted.

I'm wondering whether it actually matters to people whether their GPS device has 2, 4 or 7m accuracy. Anything with lower resolution than about 5 cm is going to be largely useless for robotic driving, etc, particularly anything worse than 2 m res - so really (and not meaning to be rude to you and your research efforts) - isn't the different resolution irrelevant, and isn't the only reason GPS users should be happy ab…

Anyone tested iPhone navigation in a gps blackout area (e.g. Near an air force base?). I used to live in Lompoc and GPS wouldn't work in most of the town owing to the proximity of Vandenberg AFB.

I wasn't aware there of existence GPS blackout areas anywhere, esp. in the continental United States. Do you have more information that would support your statement?

For what it's worth, GPS seems to work fine for a lot of people around Lompoc, CA: http://www.strava.com/rides-by-country/united-states/califor...