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Support => Troubles & Questions => Topic started by: tapio on May 22, 2020, 14:04:12

Title: No GPS fix on old and rarely used phone
Post by: tapio on May 22, 2020, 14:04:12
Hi guys,

I am having an old Sony Z1 phone as backup. Phone is always off, but when I turn it on it hardly has a GPS fix. Not sure 100%, but it seems like it gets GPS fix super slowly, like "in 20 Minutes".

- It has no sim card
- wifi is on, "Reset A-GPS" works, I get a confirmation that it has been downloaded--- but does not help
- Google location services is set to high precision
- The Locus Satellites page mostly shows like 20 Satellites, but all red. It displays "0/20".

When the device was regularly in use there were no such problems. Any ideas?

EDIT: Now I'm looking like 5 minutes on it and it has 1/16 sats.

Thx
Title: Re: No GPS fix on old and rarely used phone
Post by: menion on May 22, 2020, 14:11:31
Devices need to download so called "Almanach" with trajectories of satellites. Without it, obtain of GPS fix may be really really slow.

Check the post here on wiki: https://en.wikipedia.org/wiki/Time_to_first_fix#Scenarios

As I remember, some devices downloaded this Almanach over the web so the first cold start was a lot faster. Maybe it's common with modern devices but older like yours, as well as my still used Galaxy S2, has this "limitation".
Title: Re: No GPS fix on old and rarely used phone
Post by: tapio on May 22, 2020, 14:30:59
As I remember, some devices downloaded this Almanach over the web so the first cold start was a lot faster.
Isn't that the "Reset A-GPS" functionality (which does not speed up the process here)?
I checked with the app "com.chartcross.gpstest", same problem. It only displays GLONASS satellites btw.
Title: Re: No GPS fix on old and rarely used phone
Post by: menion on May 22, 2020, 18:41:53
"Reset A-GPS data" should do exactly this > request system to redownload available Almanach. Anyway, the app only sends this request and there exists no method to check if it was success, what is current Almanach age etc.

To be true, I've never tried to understand this better, so share with us please, if you or anyone will find/know more about it, because it's a really interesting topic.
Title: Re: No GPS fix on old and rarely used phone
Post by: Henk van der Spek on May 23, 2020, 08:17:09
30 minutes is not unusual for my backup phone (after a year or so) and place it in the open = outdoors, unobstructed sky.
Title: Re: No GPS fix on old and rarely used phone
Post by: poutnikl on May 23, 2020, 10:24:54
Aside of missing Almanach, missing ephemeris and wrong signal cases, another option is a possible issue with the device GPS hardware/firmware.

E.g. my Sony Xperia M Dual, when it was 4 years old, got the fix still fine and quick, but after 1 minute GPS position  regularly got frozen. I had to switch GPS off/on, or restart Locus, or even reboot the  device. It was unusable for navigation. I turned the GPS ON, waited for the fix, looked at the position and turned it OFF again, to prevent freezing.

----

 BTW the acronym GPS is usually used incorrectly, as it is just the US system. GNSS it the proper general term, including all other satellite systems. But as we are already used to GPS, GNSS does not have much chance.



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Title: Re: No GPS fix on old and rarely used phone
Post by: menion on May 25, 2020, 06:41:34
Ah "GPS", right sorry. It's just so common to substitute GNSS with GPS ...