All things GPS

[jeremytanner]

This reminds me of how my eight-year old son sits at the desk....

 

[qwertyaas]

After 4 days of GPS not working at all, it just starting working today. Here one one drive I recorded:

from D - Google Maps

It's a bit off at certain points but a 10-20foot error doesn't bother me at all.

 

[qwertyaas]

This reminds me of how my eight-year old son sits at the desk....

Hahahaha.

Here is my tracks from today, after 4 days of GPS not working once -

 

[lordhamster]

This was 2 hours of My Tracks running in the background while my phone laid on my desk. While I'm not satisfied with the current state of the GPS it should not be judged by this. I was indoors so I don't expect it to be dead on. I was just trying to drain the battery. I just thought it was kinda funny watching it randomly jump and move to different locations as I sat in my computer chair.
The red dot is my actual location during this period.

That actually isn't too bad. If you look at real tracks from any good old fashioned GPS unit, that is what the raw data usually looks like when the unit is stationary. They then employ tricks like averaging and snapping to roads etc, to make things seem more "normalized." I'm not saying the Captivate GPS doesn't suck, just that kind of track is to be expected.

 

[Mr. GPS]

Interesting about GPS Test, thanks for that.

That's pretty much what I'm seeing now..certainly the SNR values being much better and more stable when the phone is off and it's acquiring locks..and that noticebale increase in performance continues when you turn the wireless back on. It does give me some possible ideas as to what the issue might be.

I can't seem to find the exact chip they are using in this phone to look at a datasheet or programmers guide.. seems it might be one of three..but they're all a similar architecture. One common thing you have to do with the host processor assisted type designs that are being widely used now is control, via a Java or direct API, the tracking of the satellite signal being received and the initiation of the AGC or Auto Gain Control circuits. Basically a teeny weeny signal from the satellite comes in to the GPS device at say 50 millivolts, and to bring it in optimum peak range of the decoding circuits, let's say 0 to 1.8V you apply gain or amplification to the signal until it nicely fits in this range, so you get a good look at it. If you start this gain adjustment process in the presence of noise spikes greater than the signal you want to receive then the gain is set incorrectly for the intermittent noise rather than the required signal and there isn't enough amplification to reliably digitise and quantitise the required signal.

Conversley if you set the AGC tracking whilst the noise is completely absent then it ramps up the gain and when the noise does appear intermittently at a higher level and is amplified it hits the limits (the 1.8V say) and gets clipped, causing all sorts of nasty harmonics and distortion.. and a sudden whacking change in SNR.

It's all actually a bit more complicated than that but that's the basic principle. These AGC circuits are, as the name implies, automatic and they try and track changes in signal level to dynamically adjust the gain. So they don't do this at the slightest tiny pulse they have a programmable hysteresis or delay so it keeps a decent average value. Problem is they need something generally representative in the first place to get a coarse lock before they can get a fine one and a dirty great spike while it's setting up, say from a mobile phone transmitter, could mess that up.

All mobile phone modules, even if they aren't being used for voice or data at the time, perform periodic 'local area updates' where they send a short burst of information to the cell so that the network knows whether it's still attached and still on the same cell. This sudden transmit burst also suddenly ramps up the power consumption. In a good design a high capacity capacitor (or super cap) is used to provide this short-term peak power demand and the effect on the rest of the power rail is minimal..in a bad one it causes a sudden huge increase in load across the whole power rail and often noise on the rest of the system.

So..do other users see significant average SNR changes and better locks after first tracking with wireless off (i.e. in flight mode) ? Would be very interesting if that's a common observation and would indeed point to intermittent locally generated noise and something like incorrect AGC tracking as a root cause. Might even be fixable in the driver if they change the start point/duration/sampling interval on the AGC ..or even make sure the phone isn't transmitting noise at the time it performs the initial AGC lock. Might also explain why some users get good GPS performance and some don't..they're just lucky when it sets up the AGC.

Can we get a straw poll of the efect from oyther users with GPS problems?

Cheers

From my test, it seems that there is no significant SNR difference between flight mode and normal mode by GPS Test. I can get the first fix quickly in the wood house. My SNR range is about 25-38. I should also test the failed situations to see if they are significantly different.

However, I believe that the perceived SNR is tightly related to your description of AGC. I can reduce the perceived SNR values significantly from all viewed satellites simply by using the hands to cover the top portion of my phone. After removing the hands, the perceived SNR values go back to normal.

Thus, I did one more test. If my hands cover the top portion of the phone (I pushed SNR values < 20), then I could not lock any more in the same phone location just with differnt way of holding my phone.


This means AGC is adaptive to the patterns of GPS signals based on the settings of start point/duration/sampling interval on the AGC. Another factor we need to consider is that the perceived SNR values are from GPS TEST driver's interpretation, not from Samsung GPS driver's interpretation.

 

[fireonhigh]

im glad i never said a word about iphone4 and its in ability to make a call,,samsung has a chance to digest the apple,WTF is sam thinking,, hire any good dev from xda...but noooo,,most likely they will give us the GALAXY2,LOL, gps? spot on,everything else? well hell no,,, thats going to gal.3...im going to be hated and well im right

 

[socalrailroader]

Well, something changed, I can now lock onto satellites and it will stay locked, whether I'm still or moving, before it would often get a lock, then lose it, then get it, then lose it...repeat, and that was standing still, moving you could forget it. I can also get a lock on up to 10 satellites, indoors or out, before I was lucky to get a lock on 4 or 5. It's still not as good as the GPS in my Droid X, but it's pretty close now, though they still have some work to do on the Captivate GPS I admit.

 

[fireonhigh]

Well, something changed, I can now lock onto satellites and it will stay locked, whether I'm still or moving, before it would often get a lock, then lose it, then get it, then lose it...repeat, and that was standing still, moving you could forget it. I can also get a lock on up to 10 satellites, indoors or out, before I was lucky to get a lock on 4 or 5. It's still not as good as the GPS in my Droid X, but it's pretty close now, though they still have some work to do on the Captivate GPS I admit.

i admit it does not work...

 

[socalrailroader]

i admit it does not work...

I'm sorry it isn't for you, it is for me Is it perfect? No way, but it's a lot better.

 

[socalrailroader]

I am doing a test using My Tracks, I've had it sitting on my desk here in my room for a half hour and the tracks have varied about 30-50 feet, and never off of our property. Now, I'm running the same test on my Droid X, it has stayed locked on my position and not strayed at all. I would certainly like it to be as good as my Droid X's GPS, but so far it's doing pretty good I'd say.

Now, that said, it should NOT drift at all, the X isn't, and any good GPS shouldn't. I guess it if it keeps on my property than it's not too bad, but there is obviously room for improvement.

 

[Android_J]

I DL'd My Tracks today and tested it on a 5 mile drive. It tracked me perfectly. It even tracked me when I changed lanes.

So after testing various usage scenarios over the last 5 days, I have to conclude that JH7 did indeed fix the GPS issues for me.

 

[ulbonado]

I went outside and did a before/after comparison in GPS Status, first with everything on, then in airplane mode. Airplane mode made no difference that I could see. GPS Status would lock on 4/4 within about 30s in both cases. Later in the day it got cloudy, and then it went to 0/2 in the same location. Waited 10-15 minutes, and just because of overcast sky, I guess, it would no longer lock at all. This is with the JH7 update applied. :-(

 

[Andyman10]

From my test, it seems that there is no significant SNR difference between flight mode and normal mode by GPS Test. I can get the first fix quickly in the wood house. My SNR range is about 25-38. I should also test the failed situations to see if they are significantly different.

However, I believe that the perceived SNR is tightly related to your description of AGC. I can reduce the perceived SNR values significantly from all viewed satellites simply by using the hands to cover the top portion of my phone. After removing the hands, the perceived SNR values go back to normal.

Thus, I did one more test. If my hands cover the top portion of the phone (I pushed SNR values < 20), then I could not lock any more in the same phone location just with differnt way of holding my phone.


This means AGC is adaptive to the patterns of GPS signals based on the settings of start point/duration/sampling interval on the AGC. Another factor we need to consider is that the perceived SNR values are from GPS TEST driver's interpretation, not from Samsung GPS driver's interpretation.

I have mailed the author of GPS Test to see if he using the Java SDK (uses Samsung underlying driver) or is interfacing to the GPS API directly. I'll let you know when I have an answer.

 

[Andyman10]

I went outside and did a before/after comparison in GPS Status, first with everything on, then in airplane mode. Airplane mode made no difference that I could see. GPS Status would lock on 4/4 within about 30s in both cases. Later in the day it got cloudy, and then it went to 0/2 in the same location. Waited 10-15 minutes, and just because of overcast sky, I guess, it would no longer lock at all. This is with the JH7 update applied. :-(

Hi,

The way I did it was to turn GPS off, airplane mode on first and then GPS on to get a good solid lock, that way any AGC circuit won't be basing it's tracking on noise from wireless components, then turn airplane mode off and see what the difference is.

 

[Taero]

For those of you having a problem with the captivate in real world testing please read you won't be sorry.

I checked my gallery and every single pic that was on the phone was still there, I then checked the music and all my music was there too.

Trust me, follow the simple instructions and do a GSM reset, you won't be sorry.

Cut out this bit I just did that, (I was expecting at least a "are you sure" more fool me) and lost everything, all my apps were backed up but suckily I lost all my pictures which was a bit gutting. On the bright side I quickoffice now actually works for me, as do the other bits of the JH7 update (it said failed on me but kinda installed anyway). I'm assuming the GPS will go from awesome to zero again in a couple of days but I'll let people know then.

Either way DO THIS AT YOUR OWN RISK DESPITE WHAT WAMPRO SAYS THERE IS A RISK OF LOSING ALL YOUR INFORMATION

...unless of course it was on some kind of external SD card you didn't mention Wampro? Either that or you're damn lucky

 

[ctleng76]

Hey all,

The Captivate's GPS is STILL BROKEN in JH7 (the firmware released yesterday).

I've seen many videos and claims that their Captivate's GPS is working, but let's get some things straight:

1. GPS Devices were NOT DESIGNED TO WORK INDOORS. I do not care if you can or cannot get a lock indoors. The "GPS fix" is not addressing the signal attenuation from your roof. Please stop telling us your GPS is fixed because you can get a lock indoors.

2. The number of satellites you can see and get a lock on HAS BEEN FIXED FOR A LONG TIME. I keep seeing new videos of GPS Status showing 11 / 11 Satellite locks... this is NOT NEW and DOES NOT MEAN THE GPS IS COMPLETELY FIXED.

3. The "accuracy" value of 32 / 16 feet is WORTHLESS. Just because GPS Status says 16 feet accuracy, does not mean it is accurate! This is because the REAL LINGERING PROBLEM WITH GPS IS....

ACCURACY and RELIABILITY in Google Maps & My Tracks.

Take a drive in your car, or a walk with your GPS on using My Tracks. Did it look OK? Now do it for one or two more days. Once this track is accurate (no jumps, wanders, signal loss etc), the GPS will be fixed. I tested JH7 (latest Captivate firmware) against my wife's stock HTC Aria, and the Aria was perfect. The Captivate was losing signal, wandering off the road... sure I had 12 / 12 satellite locks the night before in less than a minute... Captivate was still near worthless for accuracy in a real-world driving test.

Anyway, I don't want Samsung to see a ton of "My GPS works!" and "This is the GPS fix!" posts, and have them stop working on the GPS problem. Please test (and post) tracks from My Tracks to verify actual GPS performance.

Thanks for this explanation. Most of the users who claim they get a signal inside probably have the "Use wireless networks" option enabled giving them the false indication that they have a lock. I also received the update, and it fixed nothing for me. At times I can get a lock within 30 seconds, and at times I get nothing at all. It will see 8+ satellites, but I never get a position back. I have seen no difference at all with the update. It is nice to have Quick Office though!

 

[ctleng76]

Cut out this bit I just did that, (I was expecting at least a "are you sure" more fool me) and lost everything, all my apps were backed up but suckily I lost all my pictures which was a bit gutting. On the bright side I quickoffice now actually works for me, as do the other bits of the JH7 update (it said failed on me but kinda installed anyway). I'm assuming the GPS will go from awesome to zero again in a couple of days but I'll let people know then.

Either way DO THIS AT YOUR OWN RISK DESPITE WHAT WAMPRO SAYS THERE IS A RISK OF LOSING ALL YOUR INFORMATION

...unless of course it was on some kind of external SD card you didn't mention Wampro? Either that or you're damn lucky

I do not have an external SD card and all my music and pictures are still there. Did you see any error messages during the update?

 

[ewingr]

Note that the poster above had the text below in his explanation of what he did that helped him:

"...enter *2767*3855#. This immediately took the phone into what he called a "GSM Reset", this was different than the factory reset, ..."

I've seen a number of posts since who say "...factory reset did not help...".

So did you explicitly follow the instructions for the GSM Reset, and not have any luck?

Wampro...are you still having success with your GPS? Also, did he indicate that the update did include GPS fix? There is a lot of conflicting information about that floating through the forum, and in responses from Samsung support folks, it seems.

 

[Taero]

I typed in the number and my phone instantly went into a screen that said "This will restore your phone to factory settings" no option to halt it, reverse, home screen etc it was basically instant, deleted everything (contacts, videos, pictures, downloads) and then went to the galaxy S screen for about 30 seconds, then booted up as if it had just came out of the box. I've read the instructions for a hard reset and know I didn't do anything like that, just the USSD code.

 

[Thuneau]

I purchased myBackup pro and backed up all my data and apps to sd.
After the reset, and reinstallation of myBackup pro, restore doesn't find the back up files on the sd.
My files browser shows no files on the sd either.
How the hell did you get your data back Wampro?

 

[Taero]

I purchased myBackup pro and backed up all my data and apps to sd.
After the reset, and reinstallation of myBackup pro, restore doesn't find the back up files on the sd.
My files browser shows no files on the sd either.
How the hell did you get your data back Wampro?

It looks like he didn't have to, it was already there, which either makes him very lucky or idk what welcome to the lost data club Thuneau, btw, how's the GPS now ?

 

[George0211]

I'll throw my 2cents in. GPS is NOT fixed, yes locks quicker but is still completely inaccurate.
Also, I talked to Samsung support this morning and they said, another GPS fix is coming soon.

 

[qwertyaas]

I typed in the number and my phone instantly went into a screen that said "This will restore your phone to factory settings" no option to halt it, reverse, home screen etc it was basically instant, deleted everything (contacts, videos, pictures, downloads) and then went to the galaxy S screen for about 30 seconds, then booted up as if it had just came out of the box. I've read the instructions for a hard reset and know I didn't do anything like that, just the USSD code.

It was a full reset for me too. I tried it and it didnt work with regard to gps. The next day I decided to return the phone so I did the gsm reset again... suddenly gps worked instantly right as I was at the att store. Im hoping it doesn't degrade but as many people stated with their new phones gps worked for a couple days then stopped. Time will tell...

 

[RickJ]

I posted the same fix here as wel,l I think the mods here sadly didn't bother to sticky it though. But central did. good to see it worked for you!

Good information seemingly has a difficult time breaching what appears to be device specific defensiveness.

But then again, no reason to sticky a workaround for a non-existant problem either .

 

[RavenFox]

We got EXACTLY what we were promised. Samsung never said they would fix GPS. They said they would, and I quote, "optimize" it. And they did. Ever so slightly, but then I personally don't think a fix is possible. The GPS hardware in the Samsung Captivate is defective. It can only be "optimized" through software, but never really fixed. Accept that.

How positive are you with this info? Are the other cell providers getting updated hardware? Can anyone check on this?