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IPhone 4S has GLONASS in addition to GPS

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Re: IPhone 4S has GLONASS in addition to GPS

#21

Post by lucaspiller »

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 ).

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 better than just GPS in these situation? I.e. Is GLONASS better in these sorts of environments?

Re: IPhone 4S has GLONASS in addition to GPS

#22

Post by omgtehlion »

lucaspiller wrote: post #21
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 ).

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…

It's all about (visible) satellite count

Re: IPhone 4S has GLONASS in addition to GPS

#23

Post by ugh »

hackermom wrote: post #9

Related: the two first Galileo satellites ( http://en.wikipedia.org/wiki/Galileo_(satellite_navigation) ) will be launched tomorrow. The claimed precision of the free-for-all service is as granular as 1 meter, with the military/commercial service claiming to reach centimeter precision. I wonder when this shows up in smartphones.

Down to 1 meter is open access, down to centimeters is commercial. I thought the open access variant would merely be on par with GPS and you would have to pay for better positioning.

Re: IPhone 4S has GLONASS in addition to GPS

#24

Post by Alex001 »

hackermom wrote: post #9

Related: the two first Galileo satellites ( http://en.wikipedia.org/wiki/Galileo_(satellite_navigation) ) will be launched tomorrow. The claimed precision of the free-for-all service is as granular as 1 meter, with the military/commercial service claiming to reach centimeter precision. I wonder when this shows up in smartphones.

Accuracy is of course important, but perhaps more important is how we build in scaleable redundancy as the number of satellites reduce. It's very frustrating when my sat nav or run keeper can't get a good signal, this inevitably leads to people dropping services or at least using them less. They key question is at what level is the service too compromised? and what's the next best alternative?

Re: IPhone 4S has GLONASS in addition to GPS

#25

Post by zimpenfish »

foobarbazetc wrote: post #10
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.

GLONASS+GPS is more accurate than just GPS, so the answer to your question is no. :)

Only if your software is aware and dealing with it correctly, I'm guessing.

Re: IPhone 4S has GLONASS in addition to GPS

#26

Post by omgtehlion »

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.

GLONASS uses nearly the same frequency range as GPS, so the answer is no.

Re: IPhone 4S has GLONASS in addition to GPS

#27

Post by 0x12 »

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 a 25% import duty on devices imported into the Russian federal territory.

Re: IPhone 4S has GLONASS in addition to GPS

#28

Post by omgtehlion »

eps wrote: post #13
singular wrote: post #6

Earlier quoted context omitted.

though off-topic and a bit of an aside, at university (I did civ eng) I learnt that it was possible to get cm-levels of accuracy out of GPS through clever arrangement of multiple sensors (for e.g. measuring the movement of buildings due to subsidence, etc.) In fact I just found a wikipedia article all about it - http://en.wikipedia.org/wiki/GPS_augmentation :)

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.

That company was Javad, no?

Re: IPhone 4S has GLONASS in addition to GPS

#29

Post by 0x12 »

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 don't understand from your table how the combined use of GPS+GLONASS would have a worse 'best case', 2.00 for GPS alone vs 2.37 for GPS+GLONASS.

Re: IPhone 4S has GLONASS in addition to GPS

#30

Post by jstclair »

0x12 wrote: post #29
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 don't understand from your table how the combined use of GPS+GLONASS would have a worse 'best case', 2.00 for GPS alone vs 2.37 for GPS+GLONASS.

I would imagine for the same reason as wearing two watches doesn't improve your knowledge of the current time. You're more likely to be within the largest margin of error (i.e., the latest time on either of the watches is probably no later than the current time), but what can you say about the earliest time? Since it's equally likely to be correct on either watch, the only thing you can do is average it. But in the case that one of the watches is actually correct, you've just introduced error.
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