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-   -   GNSS (aka GPS resp GLONASS) (https://talk.maemo.org/showthread.php?t=93209)

joerg_rw 2014-05-19 18:08
GNSS (aka GPS resp GLONASS)
 
First results from testing the PHS8 GNSS feature with our LowNoiseAmp on protoboard with N900 antenna:

https://dl.dropbox.com/u/8497686/xgps2.png

Many thanks to Sebastian/Dos1!
Just doing a GPS/GLONASS mixed mode test, results in funny jumping display for showing both systems concurrently. I guess we'll see a video soon \o/
Stay tuned for news getting updated in this post/thread.

Code:
[2014-05-19 Mon 20:53:48] <dos1> 9 GPS SVs visible, 10 GLONASS
[2014-05-19 Mon 20:54:13] <dos1> and they indeed follow [20:49] <DocScrutinizer05> 1..49:GPS; 51..99:GLONASS
[2014-05-19 Mon 20:54:17] <dos1> :)
[2014-05-19 Mon 20:56:42] <DocScrutinizer05> HAHA my guess-fu is stroooong today
/j

Dave999 2014-05-19 18:44
Re: GNSS (aka GPS resp GLONASS)
 
Cool. What do you expect in terms of fast lock. Would it be possible to compete with the fastest locks like GNlll? Or do we have any limitations in this setup? Do I expect too much here, maybe.

At least I hope faster than n900/n9. They are rediculas nowdays :D

joerg_rw 2014-05-19 18:55
Re: GNSS (aka GPS resp GLONASS)
 
http://wstaw.org/m/2014/05/19/plasma-desktoph26588.png
and that's without GLONASS, which should speed up stuff again a bit. "warm" means that the device acquired a fix during last few hours.
On N900 I recently seen time to "FIX" of <5s *indoors* and *cold*. That's clearly based on trilateration my carrier offers via 3G. Evidence: switching to 2G broke those awesome TTFF figures instantly. I bet all recent "smartphones/phablets" do same, thus the "fastest locks of GNIII"

Dave999 2014-05-19 19:10
Re: GNSS (aka GPS resp GLONASS)
 
Not super fast but OK. Do you expect faster first lock when you include glonass or just more satellites(depending in what area you are OFC).

What a warm device mean. BBQ time?

dos1 2014-05-19 19:17
Re: GNSS (aka GPS resp GLONASS)
 
Disabling and enabling GPS again needs around 10-30 seconds to fix. I'm using assistance data.

I've seen a fix from both GPS and GLONASS, but the latter one seems to be a bit weaker on my balcony :P

So it looks pretty nice. What still needs to be checked is why enabling/disabling Power/Antenna setting doesn't seem to make any difference...

joerg_rw 2014-05-19 19:37
Re: GNSS (aka GPS resp GLONASS)
 
Quote:
Originally Posted by dos1 (Post 1426004)
Disabling and enabling GPS again needs around 10-30 seconds to fix.
absolutely in line with datasheet which states 10..29s

foobar 2014-05-28 13:01
Re: GNSS (aka GPS resp GLONASS)
 
Quote:
Originally Posted by dos1 (Post 1426004)
Disabling and enabling GPS again needs around 10-30 seconds to fix. I'm using assistance data.
Do you have any figures without assistance? Using the device far away from any wireless networks is one of my use cases.

taixzo 2014-05-28 15:01
Re: GNSS (aka GPS resp GLONASS)
 
Much of the time taken to acquire a lock is waiting for the ephemeris to be transmitted from the satellite, which contains the exact details of the satelites' orbits. As the satellites transmit at 50 bits per second, it takes between 18 and 30 seconds to receive the entire ephemeris. This represents the minimum time for a GPS lock with no network connection. However, if you do have a network connection, the ephemeris can be downloaded from the internet in a much shorter amount of time; this is how network-assisted positioning works. Aditionally, the ephemeris is usually valid for 4 hours, so if you've had a GPS lock within the past 4 hours the new lock could theoretically be instantaneous.


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