All things GPS

[Mr. GPS]

Thank you for this excellent thread.

So I learned a new trick from this and other GPS threads.

1. Start AT&T Navigator.
2. Let it sit on the Terms of Service page for a few seconds.
3. Click Exit. (Don't agree, don't sign up, don't pay anything.)
4. Use GPS Test, Maps or other apps that need GPS

I get an excellent lock on all of a sudden. It's accurate and stays accurate. Typically 15-30 meters accuracy indoors, sometimes 5-10 meters outdoors or in car.

So that AT&T bloatware is good for something. More proof it's a software fix.

Thanks for this good sharing. My slogan is "Don't Use GPS without Almanac" . We don't want users to go to a bus station without knowing all available bus schedule, and just blindly waiting for a bus to the desired destination, right?

 

[Mr. GPS]

You are not crazy. Mine works without any problems as well.

None of us are crazy, just we inherit the same defect generics code. The symptoms are repeatable, managable, and curable.

Just don't be panic when the symptoms appear in your phones. You have a way to work around before the cure medicine comes up.

 

[ConceptVBS]

Mr. GPS, thank you for a fantastic analysis! Its the most productive contribution to this whole GPS issue problem. I just hated when people kept complaining about their problems and yet nobody bothered to answer the question: WHY?

This post should be stickyed!

 

[looksbetterinred]

To those saying yours works fine, have you used the turn-by-turn nav or tried to get a lock while moving? Mine gets always gets a lock while I'm stationary, but the location is almost always a couple blocks away from where I actually am. On a rare occasion, it has been exact. Once I start moving, it goes haywire.

I guess I was lucky. 2 + weeks and counting and consistently lock 8 sats with a 17' deviation stationary or moving. I will snap a screen shot on the way home today. I use Google Nav.

 

[bmoliver]

So far I have had good success with Runkeeper. I have logged 6 actual rides and a few tests. It will very occasionally wander off a bit (30 ft or so), but overall, pretty good.

 

[dockramer]

As an FYI, I have an Epic and a Captivate sitting in front of me. I had the Captivate for a week or so and had the described GPS issues. I got the Epic yesterday and the GPS works as it should. I get a lock immediately and navigation works quite well in the car.

I'm no GPS expert but there is a huge difference between the two.

 

[TXBamanut]

For me...my GPS worked well for a little while when I used the GPS Status app, but lately, it doesn't lock on or show any satellites inside or out, stationary or moving when I do that or not.

Hope Dr. GPS is right and they get things fixed without a recall...but if it's got to be a recall..hope it happens quick.

 

[BoulderGeek]

I was completely surprised to go outside into a wide open parking lot, and get 9 sats seen and lock the majority of them. Took about two minutes to work its way up to 9 anf get any lock. It settled on 10-foot accuracy at best. It hovered around 30 feet most of the time.

Firing up Google Navigator, it routed immediately to an address that it spent forever "Searching for GPS..." a few days ago.

I did change the SUPL to supl.google:7576 and SkyHook ON. No idea if that helped.

I feel better about the phone knowing that at least it has the potential of locking enough sats to use the services. The 4 year old Garmin Street Pilot on my KLR650 works much, much better, though.

I test drove an EVO for two weeks, and its satellite reception was fantastic.

 

[mullingar]

How nasty are the GPS drivers for Broadcom chips (and particularly BCM4571 and BCM4570)? Are they completely proprietary? Are there any open source or reverse engineered alternatives? Are their SDKs available to anyone?

Also, are the drivers completely in kernel-space or they have parts in userspace?

EDIT: found (partial) answer to my question...
damn! they are in userspace and apparently closed source. I guess we have to wait for the samsung devs to fix (more like rewrite, I guess) that part of the driver. Since it is their developers, and not general google/android's, I guess the driver will be buggy for long.

 

[android4rumuser]

I agree with many of the readers on this forum that this thread has been one of the most productive, most informative and best logical explanation seen so far for the issue we are all facing.
Thanks Mr. GPS. If I were to be Samsung, I would already know what is my action plan after reading this thread.

 

[dantheman2]

Google Navigation works to invoke Task 0 and 1. Google Maps does not. Most people try Google maps, it doesn't work, then they come to this board sending a global "GPS doesn't work on the Captivate" thread.

Same issue on the Epic 4G forums if you go look at their forums.

Also, Task 3 is a sensitivity issue either controlled by the driver or software, or it is an actual limitation of the hardware. I have a coworker with an iphone 4. He gets a GPS lock really fast in his office (with windows). I have another co-worker with the EVO. It too gets a lock indoors in the same type of office with a Window. My captivate does not get any or very little sat. signal (using GPS Test) to even get a lock (task 0 and 1) yet to do task 3. So it is combination of all the tasks that is not as good as other phones. This term is more generally called "Poor GPS Performance".

Bottom line. If you really want a good, fast GPS without holding your breathe from Samsung, buy a different phone.

If you know how to work it, you can get the Captivate to under 5m most of the time.

Dan

 

[The Sopranos 16]

@Mr. GPS: Thanks for the insight! This thread was very helpful to understand the GPS process and where our phones fail. I was wondering if you could help make sense of the fact that new or recently hard reset phones tend to get good GPS performance for a while. The performance then tends to degrade over time until it us virtually unusable without one of the "cheating" methods you mention. Do you have any thoughts on what causes this?

 

[looksbetterinred]

I took these at lunch. The first is in the paring lot and the next as my friend drove us to lunch. I haven't done mods or changes to any of the settings noted here. I am rooted though.

http://i939.photobucket.com/albums/ad237/kyblugrass/snap2100901_111352.png

 

[Mr. GPS]

I try to provide the explanation of the same perspectives of different sides about Capativate GPS issues.

We need to examine the historial usage and environment conditons of those "no-problem" Captivate phones

My assumptions:
1. Samsung GPS driver did not execute Task 0
2. For Task 1, it only works under very good satellite signals.

Those "no-problem" Captivates, which still have defect genetics codes, could be operated under good signal environemnts initally and collecting relevant almanac in that region by succcesfully executing task 1. After sufficient almanac is cached in the phones, the "no-problem" Capativates only need to operate task 2 and task 3 and there is "no problem" shown up in that region.


Why I think the assumption 1 is true:

After you turn-on GPS (location and security setting), there is no satellite symbol on the phone screen or blinking. There is nothing to suggest that GPS receiver is trying to collect almanac and lock the satellite at that moment after turning on. Only when you start geo-taging camera, google maps, or others, the satellite symbol is shown up and trying to lock (note this is task 1, not task 0)

Compared to car GPS systems, when turning on the car GPS devices, the first thing they do is to get GPS status (which is a portion of relevant almanac to current location). I do not know why Captivate does not do that automatically, and it should at least have an option to users: GPS-on with/without self-initialization. By default, Car GPS systems do that.

Why I think that assumption 2 is true
From my AT&T store testing, the Captivate phone near glass door can be trained by Samusung labtestMode, which uses the Samusung driver for executing task 1, but the one inside the building with weak signals doee not work that way.

I believe that we do exist "no-problem" Captivate phones since they operated in Satellite signal rich environements at the initial stage and got
good "nutritions" (almanac) to compensate the defect generic code.

 

[looksbetterinred]

I'm not sure what category mine falls into. I will say it is not the quickest picking up the sats as I would like. It will take about 45 sec to 1.5 min to pick 8 up. That being said, with a 16 - 20 foot deviation, I am able to navigate well with google nav. The short of it... I'm content with the performance, although it could be improved AND I am not sure how it would operate in different parts of the country. Just for ref, I am in southern Kansas.

 

[Mr. GPS]

@Mr. GPS: Thanks for the insight! This thread was very helpful to understand the GPS process and where our phones fail. I was wondering if you could help make sense of the fact that new or recently hard reset phones tend to get good GPS performance for a while. The performance then tends to degrade over time until it us virtually unusable without one of the "cheating" methods you mention. Do you have any thoughts on what causes this?

Please explain what do you mean 'hard reset phones"? Do you mean you remove GPS data in the LabtestMode?

 

[Mr. GPS]

This is for Mulligar:

Could you also check if there is AT&T GPS driver or GPS Status GPS driver in your phones?

Thanks.

 

[DT]

Some really outstanding analysis in this thread!

I've been saying some of this as well (though not with the level of detail regarding the GPS operation). Particularly the hardware/firm >> drivers >> OS >> App considerations. I don't think any of the variation we've seen is hardware related (I think there's a single, good implementation of the BCM4571 in this phone, and the other SGS products).

I believe there's a flaky driver implementation, that creates a real inconsistent (i.e. hard to debug) pattern of operation; combined with peoples location, settings, cell/WiFi proximity, and order of use of GPS related apps, etc.!

Especially now with Mr. GPS's contributions about how the GPS layer works, I totally understand what particular operations are failing at what point in the GPS activity.

 

[looksbetterinred]

Could you also check if there is AT&T GPS driver or GPS Status GPS driver in your phones?

Thanks.

I'm not sure how to do that.

 

[Mr. GPS]

I'm not sure how to do that.

Sorry I was asking member Mullingar to check since he found the Samsung GPS driver in Android

 

[The Sopranos 16]

Please explain what do you mean 'hard reset phones"? Do you mean you remove GPS data in the LabtestMode?

I usually read up on XDA-Developers and it has been said numerous times that performing a factory data reset restores gps functionality temporarily. The gps basically performs the same way it did when the phone was brand new (and for most people, including myself, the GPS worked fine at first). I've found that removing GPS data in LBSTestMode does nothing and I have never personally did a factory reset. I was just sharing what others have reported.

 

[ulbonado]

First off, a heaping helping of thanks to Mr. GPS for a little light in the darkness here.

You're obviously more expert (by a lot) on these matters than I am, but I do still have one reason for being concerned that there may be at least some hardware issue at play here in addition to the software problems you describe.

I was at lunch on Friday with my boss, who has an HTC Evo. We were in a restaurant, which was a standalone brick-faced, steel frame commercial building. We were in the interior, probably 40-50 feet from any window or door. We put our phones on the table (his Evo, my Captivate) and both launched the GPS Test app. His saw 6 satellites with 4 fixed almost immediately-- my Captivate saw nothing at all for several minutes, then eventually saw 1 sat, but couldn't lock it. After lunch we repeated the test out in the parking lot. By the time the GPS Test splash screen had cleared, his already had 6/8 and went to 8/10 within a couple more seconds. Captivate again started with nothing, gradually adding one at a time. Eventually Captivate did see 8-10, but had a lot of trouble holding a fix. His was steady at 8/10, mine kept going 3/8, 2/8, 6/8, 2/8, 0/8 etc, with the accuracy fluctuating wildly as the sats were acquired and lost. Also, the SNR on the Evo was 30-45 on most of the sats, while on the Captivate it was in the 20-35 range, and kept bouncing up & down, while the Evo's were pretty steady (not completely steady, but a lot more so than the Captivate).

Since GPS Test appears to be displaying the raw sat data including which sats it sees and the SNR on each one, the fact that the Captivate had weaker signals even once it saw the sats said to me that it had inferior hardware, like maybe an insufficient or poorly placed antenna. Am I way off base here? Do the symptoms that I saw sound like they can be fixed with a firmware or driver update? Maybe with better software the data that it got would be sufficient to lock more sats and derive a good location, but the fact that the SNRs were always worse just seems to say to me that no matter what you do in software, you're always going to have less to work with. Ie., a hardware problem of some sort, antenna being my best guess.

 

[Mr. GPS]

I usually read up on XDA-Developers and it has been said numerous times that performing a factory data reset restores gps functionality temporarily. The gps basically performs the same way it did when the phone was brand new (and for most people, including myself, the GPS worked fine at first). I've found that removing GPS data in LBSTestMode does nothing and I have never personally did a factory reset. I was just sharing what others have reported.

OK I got it. Factory reset only means that the phone is back to the original phone condition, It is still with defect genertics driver code.
How to use the phone from that on become important to avoid the GPS issues

The message is that you need to feed enough "nutriions" (almanac about your region) to that phone

Two ways:
1. By external intelligent programs: GPS Staus, or others
2. Operated only in signal rich areas for a while

 

[Segfault]

And if they are fixed, then why can't the get the fix out for the Captivate now?

I'm still hopeful that September will bring the fix.

It's way easier for Verizon to apply an updated GPS driver to a phone that hasn't been released yet than it is for AT&T to coordinate a release for thousands of phones that are already released. AT&T needs to regression test the fixed driver to make sure it doesn't break anything else. Then they have to co-ordinate the release process for it. I'm sure they are also weighing whether or not its worth releasing this fix as a separate fix or if they should just include it with the Froyo update. I'm sure AT&T would rather just do one update, its less work and it costs less.

 

[onthefenceguy]

I just got my Captivate yesterday from the AT&T store. After reading these posts I'm not sure if I should return it and wait for a definite fix. Initially I had my settings at "Use wireless networks" unchecked and "Use GPS satellites" checked. Maps and GPS Test couldn't lock on to satellites after 5 minutes with clear sight of the sky. I changed settings so Use wireless networks was checked in addition to "Use GPS satellites", rebooted, and launched Maps. Maps initially locked on to my location accurate to 60 meters and the GPS icon was throbbing. After about 15 seconds I got a GPS lock and maps zeroed in on my actual location. Now if I uncheck "use wireless networks" I still get a GPS lock, even after reboots.

I tried navigating to a location where I knew I would go from 3G to Edge and it kept tracking me onto Edge. When in an Edge area I rebooted and still got a GPS lock.

Now I'm at a loss whether I still should return it (I have 3 days trial left) since things seem to be working fine. Any advice?