Help GPS does not lock, despite many satellites visible

[mfan]

Hi there,


as you see in the attached screenshot (the app is "GPS Test"), I have many satellites in view, many in use as well, but I get no fix. The GPS does not lock at all. (Samsung S3 Galaxy, a 3 years old phone running Cyanogen-mod with kernel 4.4.4).

Since I _do_ have satellites in view and use, I suppose this is not a hardware (e.g. damaged GPS chip, bad contacts, untight screws), but some kind of a software issue.

Any ideas?
Thank you very much!

 

[tube517]

I no longer have an S3 but could it be the ROM?

Some custom ROMs may affect GPS. Again, I have no idea because I no longer have the S3.

 

[AZgl1500]

there is a possiblity that even though it sees those satellites, it just does have a proper ephemeris loaded.

Install this app, it will download the proper ephemeris from NASA's servers, and then it will lock onto the sats...

* GPS Status & Toolbox - Android Apps on Google Play

 

[mfan]

Wow! The app "GPS Status & Toolbox worked instantly by just downloading and running it. The GPS locked within seconds.

After hours and hours of searching, such an instant relief is almost hard to believe.

I don't really know what had happened to my phone and created the trouble. I didn't do anything major in the OS, just normal use. Yes, I am rooted and running a custom rom, but this didn't change since more than one year. Every couple of months, I do a cache reset to keep my device clean and fit. I hadn't done one, I tried _after_ the GPS stopped working, but it seems to be irrelevant.

Thank you very very much!!

 

[AZgl1500]

all that happened was:

the phone was out of sight of the sats for a few hours....
and sats being sats, they moved ????? yup, they were no long where they "belong"...

now, the phone's GPS receiver has to find one sat that it can sync-lock into, and then it has to wait until that sat sends down a full copy of the current ephemeris table.

that takes a while, and it depends first on how long it takes the phone to find/lock onto a sat that it can decode the downstream data.... once it does, it can then start looking for all of the other sats.

2 sats will locate you north of south of the equator.

3 sats will locate you within a few hundred feet.

5 sats will give you a pretty decent idea of your Altitude.

7 or more will just zero in finer and finer to your actual location to within a few meters.

I typically can get 13 sats if I am outside in the clear. You get 13 sats locked in, and your phone can display accuracy right down to about 1 to 3 meters.... lots of fun to watch that app.

Walk inside a building and stay there for a while, and the phone don't know where it is anymore.

 

[mfan]

Thanks again for the feedback!

I 've been watching my cellphone gps behaviour in the last days. Sometimes it works, sometimes it doesn't. When I say, it doesn't, I mean that not even the app GPS status manages to lock, even if I maually update the AGPS data. I am trying to figure out a "behavioural pattern", not succeeded yet. (I have the suspicion that rebooting and directly letting GPS Status run has high chances of working).

I understand what you are talking about concerning the position of the satellites etc. It all makes sense. But it has always been so. I mean, the satellites were always moving. However, previously, I did not need the GPS Status app. My gps simply worked. Now (since a few weeks, I mean) it doesn't.
So, the question should be: What happened to my GPS receiver/GPS driver/other OS components and now it needs the app GPS Status in order to (sometimes) work?

 

[AZgl1500]

I am to assume that you are always 'outside in the clear" when this problem occurs?

that is, not inside a big concrete structure? Office, hospital, etc...

 

[senoritafish]

Thanks, I've been having a similar problem in the last month or so - i.e. apps like Runkeeper never get a coordinate lock, Waze seems to just jump from cell tower to cell tower. I'll give this a try and see how it works.

But like OP, I don't know what I did to make it stop working. I'd thought maybe I just had too much stuff on my phone, but I deleted apps down to before I started having the problem and it was still the same.

Edit: it did work on my phone - thanks, I'm getting a lock now. Tried on my Nook and discovered it has no compass sensor, which I did not know. Rats.

 

[senoritafish]

Let's rephrase that - I do get a lock but sometimes it takes up to 10 minutes, and it doesn't seem to work for all apps (i.e. Runkeeper never gets a lock even when the GPS app does). Is it possible for the GPS sensor to stop working? I'm thinking of replacing my LG Tribute as I use my GPS a lot (navigation, fitness apps, geocaching) and having to wait 5-10 minutes for a satellite lock is just getting too frustrating.

 

[Slug]

Is it possible for the GPS sensor to stop working?

With electronics anything is possible. I saw a Samsung Galaxy S7 DOA out of a sealed box today.

If location is active then the GPS receiver should update the almanac (the
ephemeris table mentioned above) automatically at regular intervals. Problems usually arise when the receiver isn't used for several weeks - the device then has to (a) gain lock on at least 3 satellites and then (b) download a new almanac from one of the linked satellites. On my handheld Garmin this can take up to 20mins depending on climatic conditions and satellite maintenance.

 

[AZgl1500]

If location is active then the GPS receiver should update the almanac (the
ephemeris table mentioned above) automatically at regular intervals. Problems usually arise when the receiver isn't used for several weeks - the device then has to (a) gain lock on at least 3 satellites and then (b) download a new almanac from one of the linked satellites. On my handheld Garmin this can take up to 20mins depending on climatic conditions and satellite maintenance.

This is precisely why I always start up GPS Status & Tools before I use any app that needs the GPS to be accurate "right now", and not 20 minutes from now.

GPS Status and Tools polls the NASA servers and downloads the ephemeris table so fast, if you are not watching the screen very close, you won't even see that little blip popup stating "downloaded table".

The GPS receiver then knows exactly where the sats are, and it can get a lock with only 2 sats in view... not a good lock, but locked.

If it gets 3 or more, you are good to go for taking a trip on the highways.
If you want to have a Hiking GPS app track your footsteps and leave a Cookie Crumb trail, then you will need about 7 sats in view to get 9 meters or less accuracy.

I have seen 3 meter accuracy on my GPS Status & Tools app on some occasions. Depends on how good a view of the sky the GPS receiver has. I once counted 13 sats locked in...

* GPS Status & Toolbox - Android Apps on Google Play

 

[senoritafish]

Problems usually arise when the receiver isn't used for several weeks - the device then has to (a) gain lock on at least 3 satellites and then (b) download a new almanac from one of the linked satellites.

Thing is 1) I always have location on, 2) I use this thing every day, 3) this was never a problem before maybe three weeks ago. As I said, I thought maybe it was because the memory might be getting too full, but I deleted stuff down to before I had the problem. Now I wonder if the short time I had Pokemon Go on there damaged it or something. It's a cheap phone so I wouldn't be surprised.

This is precisely why I always start up GPS Status & Tools before I use any app that needs the GPS to be accurate "right now", and not 20 minutes from now.

GPS Status and Tools polls the NASA servers and downloads the ephemeris table so fast, if you are not watching the screen very close, you won't even see that little blip popup stating "downloaded table".

Oh, I see the blip alright, it just takes awhile before everything clicks in. I would start it that early, but GPS tool can't seem to find satellites very well while I'm at my desk, even though I'm near a window, and then it loses it again when I walk downstairs to the door.

If it gets 3 or more, you are good to go for taking a trip on the highways.
If you want to have a Hiking GPS app track your footsteps and leave a Cookie Crumb trail, then you will need about 7 sats in view to get 9 meters or less accuracy.

As I said earlier, Waze navigation seemed to work almost immediately. Alas, I've become very fond of Runkeeper's crumb trails, and it used to lock on just a few yards out the door. Now it takes my entire lunchhour walk, so that must be what's going on. I'd ask my walking buddy to wait, but she gets impatient, because her phone (iphone) has no such problem.

Anyway, I've had it for a year, I think I got use of the $40 I paid for it so maybe it's time for a new one. I'll give this one to my son, who doesn't much use GPS and has been looking at a broken screen for the same amount of time.

Thanks much for your thoughts, folks.

 

[AZgl1500]

Not all phones are equals, even between multiple copies of the same exact model/brand.

One might have a super sensitive GPS receiver, and the next one is a dud....
from what you say, you expect it to stay locked while you are inside a building....
that just is not going to happen, and being next to a "window" does not prove anything, you only catch maybe 2 or 3 satellites that way...

until you get outside in full view of the sky, there is no point in activating GPS Status and Tools...

I have a Garmin 2797 GPS, if it has been left off for over a week, it takes it a long time to find the sats....
that can be very aggravating if you have a need to jump and run.....
so, when I know that I am going somewhere tomorrow, I go out the night before and enter in the trip.....
that way, all I need to is crank up the car, and start driving,.... the GPS will catch up with me 2 or 5 miles down the road sometimes.

usually though, it is on track before I get out of my yard, my driveway is 320 feet long and gravel, so I drive slow...