yashsingh1/xdaforums huggingface dataset:
[Epic 4G General] boomerbubba:
I don't have an automated solution to offer there. I plan to install and experiment with the Tracker utility, which does lots of things. I'm quite sure it could automatically launch GPS Status when Google Maps launches, for example. But I don't know that it could script the execution of the requisite commands within GPS Status.

The only unit I have to compare is my G1. Based on your experience, I have tried again to replicate a decent side-by-side test using the GPS Test utility. I stared at the two phones for about 15 minutes, and my perception is for a rather modest difference of the average SNRs, perhaps 5 DB or less. The same is true for peak SNRs of the individual satellites. And even the relative pattern of the satellites' bars does not seem well correlated between the devices. The problem with this methodology is that because I am just looking at the GPS Test app's GUI on each phone, and each GUI is being refreshed very rapidly, it is hard to get a rigorous result. What is needed is a real-time logging utility that would run on any Android phone, capturing all this detail with precise timestamps, so it could be analyzed offline.

Again, I still wonder how seriously to take the reported SNR numbers, which are not a priori values but themselves are calculated by the phones' firmware. We know that a similar calculation -- the 30.0 meter accuracy estimate -- is itself buggy. I don't believe that on the Epic, so why would I necessarily take the calculated SNRs at face value? Maybe they is real, maybe not.

Finally, the SNR calculations are just an intermediate indicator. Healthy SNRs are not the end result that users seek, but a means to an end. The final result is the bottom-line accuracy of the lat/lon coordinates themselves. My testing of those coordinates in simultaneous tracking comparison is showing that actual accuracy -- relative to my G1, which I consider to have good GPS performace -- is as least comparable. The Epic passes such benchmark tests for me, which Vibrants did not.
[Epic 4G General] boodies:
yeah you need to stop whining dude, it won't get you anywhere, grow up. Sammy said a fix is coming so stop naggin. Oh and please stop calling everyone who disagrees with you a troll. WTF? lol
[Epic 4G General] sling:
Were did you get info Samsung fix is on the way. Ive searched the web not finding such statement from them since release.

I have found they've blown Vib & Captive users off on this issue leaving them hanging for some time.
[Epic 4G General] robl45:
exactly believing a company when they say they are doing something is like believing your wife will come back after she divorces you, it most likely ain't gonna happen.

What do you want samsung to say? we are not doing anything so please return your phones? the worst part is, the more problems that creep up, the less likely samsung is going to upgrade this to 2.2 and rather just go to another phone.
[Epic 4G General] aero1:
Boodies? You are whining and crying for what? You are making nonsensical posts.

Samsung never said a fix is coming -- they said it was fixed before it launched. Since you seem unaware of what Samsung is on the record saying and have it backwards and wonder why people are laughing at your posts! :D

Example of nonsensical post! Turn on tower triangulation to test satellite reception? LMAO you fell for it!

Spot on Sammy claims it is fixed.
[Epic 4G General] sling:
Very true in some cases lol

Samsung has a bad track record of acknowledging issues as well as fixing.

How about them acknowledging issue letting their customers know its being worked on.

Remember they stated issue would be fixed before release that's a big factor with many losing what little faith they had in them now.

Samsung has a terrible track record official statement from them would be a keeper

ya problems will creep up...heck there will be problems that weren't present in 2.1 that will be in 2.2 its the way software upgrades work.

The GPS issue different though ,It was supposed to be taken care of before release and wasn't so its well over due....that goes for Vib and Captive as well
[Epic 4G General] sling:
Yep yep which is why they need to step up with Official statement and make fix happen fast , A couple members in this thread have a hard time excepting that...its like they love Samsung or something.

If they don't hop on it fast many current owners will take back within 30 days & those thinking about purchasing will take a pass
[Epic 4G General] sling:
heheh A little comedy to thread.

Iphone gave away cases to solve antenna issue

Samsung needs to give away gps Hockey pucs
[Epic 4G General] APOLAUF:
Unfortunately, once the GPS has decided to fail, clearing the ephemeris data doesn't seem to fix anything. I sat there in GPS test, cleared and re-downloaded multiple times, and it just sat there with 1 satellite locked, the rest visible but not locked. After 2 minutes of poking the screen to keep it on, I ended up rebooting to solve the problem. Wish that were a simple (but unecessary) fix.
[Epic 4G General] boomerbubba:
Sorry to hear that. I had hopes for GPS Status (not GPS Test) as a workaround. Sounds like rebooting may still be the only certain workaround. (I have only experienced the failure to lock once, so that is all I have been able to try.)
[Epic 4G General] aero1:
1. Thank you for all your work.

2. I can confirm that "manage a-gps state""/aGPS xtra data": reset, reset and download, and just downlaod sequences, are not kicking the GPS into gear.

Perhaps some other sequence of usage is clearing cache but with little predictability? I know What I do know is after about one week with three Epics we have had several total failure to fix, even with claims of 8 birds. even 30 minutes later, (double the max time needed for almanac download with birds in sight) no lock, no sats "in use"

I have three. By tomorrow I feel I may only have two, but is there some sequence we can test to see if this is the case? I do find failures are occurring say half a day after successfully invoking a LBA (location based application),ending the application, and retrying about 8 hours later.

If stale ephemeridal data en cache maybe one of the issues I suppose we should be on teh hunt for an existing utility or someone with the skill to build one to force certain flush and/or renewal of the cache to fully test the theory
[Epic 4G General] aero1:
I would like to point out that from various early reviews it is clear that the reviews a week before release were likely done with different firmware. one can tell because the reviewers are not noting the features removed in the retail release firmware. I think that these people may have been having trouble with GPS but were assured by Samsung flacks that changes would come with the retail release.

the first ind depth professional review I have seen with an actual purchased retail unit SLAM GPS performance on the Epic:

http://www.anandtech.com/show/3891/samsung-epic-4g-review-the-fastest-android-phone/10
[Epic 4G General] aero1:
you mean "gps status" I think, not "gps test".

I am looking at the samsung stack "gps setup" panel via *#1472365#

There is tab for "xtra settings"

now gps status rel 3.4 settings and configuration/gps & sensors/manage a-GP state/ brings up "A-GPS XTRA data"

OK, on on samsung gps setupe" tab extra settings, I see "enable xtra", "disable xtra", and "enable automatic download" are ALL unticked by default.

Is it possible that one or several of these on sammy's gps setup might need to be ticked to clear cache through gps status?

Also are you on hot start? I am thinking of trying "Warm Start" Warm often assumes almanac ok but need for new ephemeris. that might do something positive and force attempt at fresh assistance, as well. I will try some testing tomorrow
[Epic 4G General] boomerbubba:
My reply cross-posted from other forum, just to close the loop here:

As for your suggestion about trying a Warm Start, I wondered about trying that myself. Candidly, I'm still trying to comprehend the difference between Warm Start and Hot Start (the default). I just understand that Cold Start always forces a fresh initialization that can take a long time. In my spare time I have been plowing through this reference, but have not assimilated all that I need to.
[Epic 4G General] APOLAUF:
Oops, I meant GPS Status, my bad! But yes, unfortunately, problem still exists.
[Epic 4G General] boodies:
yeah dude stop whining :)
[Epic 4G General] NeonMonster:
From GPS being completely off, then turning it on, within 30 seconds my Epic is able to find me.

Its off by about 15 feet. It placed me in my neighbors house. :P Which isn't great, but isn't horrible. My Nexus was always able to pinpoint exactly where I was almost instantly.

Hoping the GPS fix comes out soon.
[Epic 4G General] aero1:
Oh our resident troll. again. LOL :D

Everyone thinks you are whining and trolling, no one thinks I am.

Do you realize why everyone is laughing at you? or are you just used to it?

This is samsung we are talking about -- they have the number one worst record on updates. (another thing we had to school you on with facts here))

You cracked everyone up with that on a gps diganostic thread! You don't even understand why it must be OFF
[Epic 4G General] b1indsided:
My gps works fine and fast.
[Epic 4G General] dwyw42:
Same here. Made sure to disable WiFi and WiFi/Cellular location and I was able to get 8 satellites locked in under 10 seconds. Then I toggled GPS off and on, and loaded up Google Maps and was able to get a very accurate position within a few seconds. Walked all around my concrete patio and it positioned me perfectly on the Satellite view. I also tested it out at the dog park near me and it worked flawlessly.
[Epic 4G General] aero1:
I t isn't completely broken but has substantial problems across all the current production. comprehensive reviewers using testing application are universally finding problems. Comparisons with different models and the same software in the same location all mirror those problems.

Please post a picture showing eight satellites locked with GPS test or GPS status application. Epic is routine showing eight to ten "found" but only three to four "in use" (Locked)

and it is a moot point since I spoke at length with Sprint Advanced Device support (top level trech for any Sprint device) not only can they duplicate several fail modes. Tehy have their own tickets into Samsung and are requesting fixes for four separate GPS issues on Epic. One minor (bogus accuracy number of 98'), two moderate (poor GPS SNR, failure of AFLT in some modes), one severe (cache not flushing) causeing no fix after one day.
[Epic 4G General] boomerbubba:
For the record, my Epic often uses eight or more satellites, according to GPS Test and GPS Status. I have seen as many as 12 out of 12. When running simultaneously against my G1, the number of satellites locked on the Epic is generally as good, sometimes even better, even though the Epic's SNRs are moderately lower.

So as far as I can tell from testing, the Epic does have several distinct GPS problems, but a low number of satellites locked in general is not one of them. (I do understand that when the cache bug occurs after some period of inactivity, one symptom of failure to to achieve lock will be very few satellites shown as used. But that is a separate bug that occurs only under certain circumstances, not a general condition.)
[Epic 4G General] dwyw42:
how do you tell found vs in use? is that the asterisks? if so, which is which?
[Epic 4G General] boomerbubba:
If you are looking at the histogram display in GPS Test, the colored bars are in use, the gray bars are not. The summary totals are shown in the corner of that display. In GPS Status the totals are shown as a ratio: x/y, where x is number used and y is number in view.
[Epic 4G General] dwyw42:
Here are the screenshots from GPS Status and GPS Test. This was from inside my office (although next to a large window) so the SNR is pretty crappy. I can take some more outside when I go home if you'd like :)

It's kinda interesting that the Sprint Navigation/Telenav still exhibits the 10% bug on my phone though. Maybe it's a bug in Telenav?
[Epic 4G General] boomerbubba:
Dunno about Telenav. I have never used it, although I tried Sprint Nav once. I never found the diagnostic reading you and others describe. Where is it?

I trust GPS Test and GPS Status, which I'm pretty sure read the Android API's listeners directly and are utilities specifically designed for this purpose, more than I would Sprint Nav's feature. As I understand it, that feature purports to represent GPS perfomance as some kind of percentage. That is intellectually suspicious to me in the first place, sort of dumbing down the actual data by some method intended to make end users think they understand something they don't otherwise grasp. (Sort of like how signal-strength "bars" have no scientific a priori meaning, but users quote them like they do.)
[Epic 4G General] dwyw42:
Sprint Nav is just the Sprint branded version of Telenav. It even says "telenav" in the corner above the menu. But the reading is under Share & More > 8. Diagnostic Tools > GPS Status.
[Epic 4G General] boomerbubba:
Thanks. I will try that later. How did you make your screenshots? The only such apps I know about require a rooted phone. Or did you just use an external camera?
[Epic 4G General] dwyw42:
My phone is rooted ;)
[Epic 4G General] hydralisk:
You can take screenshots using the app called "shootme" as it works on NON rooted epics. I didnt root my phone, and yet I can use it. *shrug*
[Epic 4G General] dwyw42:
Here are the screenshots from home. SNR still isn't that great but 8/8 birds locked.
[Epic 4G General] boomerbubba:
I think those indicators looks pretty good.

As for the SNR levels being reported, I take them with a bit of skepticism. There is not an a priori SNR being measured by some external meter or probe on the phone. Rather, the SNR estimate is calculated in the firmware, just as the imputed accuracy (30.0 meters or 98.4 feet) is supposedly being calculated. We know that the imputed accuracy number is the result of some bug. So why would we necessarily assume there is not also a problem with the SNR estimates?
[Epic 4G General] aero1:
seriously guys we are a step beyond that. it isn't about birds seen vs in use after a boot but birds seen vs in use after ephemeris is expired. teh problem is if you shut off pstion requests over four hours or often even less teem if you stop LBA GPS data requests from a location different from last location, this is a condition in which you consistently get this very low number in use vs in view and time does not repair it, (as it would on standalone GPS) only SM restart does (almost certainly by dumping the cache.

And the SNR is reported directly, the SM calculus is a ratio. may as well say debug db for cdma, evdo and wifi is not useful becuase the phone is not a calibrated probe. it is useful.

This is very different than the 98' 30 meters issue which is NOT a caculus, but has to do with "fix.coarse " script have the value hard coded in for several of the coarse (but course, but course as in coarse vs fine in adroit location scripts) values. That coarse vs fine location data reported by android devices is USED differently by Applications, and Samung appears to have set several methods of varying accuracy at one level of 30 meters. For example, the most basic terrestrial location report, (required by law) is location of the a single tower the phone is in contact with. With that I don't see 30 meters, I see 3000 meters.. If it is single tower plus signal strength the location is slightly more refined. If it is two towers, slightly more, then three towers, then towers pulls timing calculations on towers, then towers plus one satellite, etc as you go up the ladder toward lower dilution of precision. (H/D/P/DOP)
[Epic 4G General] dwyw42:
how long does it take for my ephemeris data to expire?
[Epic 4G General] boomerbubba:
Do you know this for a fact about the way the Broadcom BCM4751 chip works? That there is a direct output from the GPS chip's hardware?

I do not pretend to know. But I am aware, just from general comments by a Broadcom employee posting on xda forums, that the internal logic of that chip is a hybrid of low-level software (one can call it a low-level driver, or one can call it microcode, but it is flashable firmware) working with discrete hardware elements. I also know, from the same source, that the firmware fixes on the Galaxy S devices were being implemented by engineers at both Samsung and Broadcom. Obviously, there is at least one known bug in the new work they did for the Epic GPS's internals. I suggest that there may be more than one bug, or even multiple effects of the same root cause, and they might have borked the reported SNR levels.

It does appear to me anecdotally, just from my memory of testing on Vibrants and my perusal of other threads testing other Galaxy S variants, that the reported SNRs may be modestly lower on the Epic than on these other phones. (For example, see screenshot on this Captivate, which to me show SNRs slightly better than I typically see on my Epic.) So it is plausible that something has changed to reduce the reported SNRs in the Epic implementation. That could be hardware (different antenna design because of the different and fatter form factor?) or it could be in the new firmware installed by Samsung and/or Broadcom.

Further, the SNR is not the final result, but an intermediate indicator.

Regardless of the reported SNRs, my experience (unlike yours) is that the number of satellites used by the Epic for a fix is comparable, sometimes even better, than the number used on my reference benchmark, the G1.

[Edit: Also, when running GPS Test side-by-side with my Epic and my G1, I notice that it is not just the height of the SNR histograms that differs, but also the shape. Bird-by-bird, relative to each other, the SNRs can vary in the same snapshot of time. This uncorrelated behavior, once again, leads me to suspect some voodoo in the logical processing, not just weak signals across the board.]

Different chips may be more or less successful in processing weak signals into the real final result, which is lat/lon coordinates. My own empirical testing of those final results, in the form of lat/lon tracks captured by My Tracks simultaneiously on both the Epic and a G1, shows that the actual accuracy is comparable even though the reported SNRs seem to be several DB less on the Epic (just not as much less as you perceive from your own testing).

In summary, I don't know the full story about the Epic's SNRs. But I remain skeptical of the reported numbers, and don't consider the SNR comparisons across platforms, each with different meauring logic built by fallible programmers, to be definitive. And ultimately, I care much more about the actual tracking performance than about such intermediate indicators.
[Epic 4G General] boomerbubba:
More about SNRs in general

I am not a GPS expert, but I have been researching this issue. Everything I learn reinforces my impression that methods of calculating SNR figures on GPS handhelds are neither simple nor uniform.

This paper, based on a survey of GPS manufacturers, expressly warns against comparing SNRs across manufacturers (or even across products from the same manufacturer).

One GPS manufacturer, Trimble, called these SNR numbers "Arbitrary Mystery Units" instead!

My subjective impression of the Galaxy S testing is that the methodology for computing SNRs has even varied across branded variants of the same basic model. That is, SNRs may be computed differently on the Epic, a later release with later low-level firmware, than it is calculated on Vibrants and Captivates. It certainly seems to be calculated differently than it is on my HTC G1, just based on eyeballing the histograms in GPS Test.

More than ever, I view comparisons of SNRs across platforms as a tenuous excercise. It is really no more useful than comparing signal-strength "bars" across phones. Different implementers can effectively make up their own scales.
[Epic 4G General] rmt5:
Just wondering if there has been any progress in gaining information from Sprint/Samsung on this front?

And is there anything you suggest the less tech-savvy among us do to keep this problem in the forefront of their minds? (i.e. a phone number to call? what specifically to say? let them know I'll be trading in for an Evo if information doesn't come soon?)

Edit: Perhaps we could at least edit the wikipedia page, which reports that all GPS issues have been resolved in the Epic.
[Epic 4G General] boomerbubba:
That's a very good question. Aero1's account of talking to Sprint's level 3 support is very credilble, so I do not doubt that Sprint has opened tickets with Samsung over the specific issues that have been identified. What we know nothing about is Samsung's response.

BTW, I doubt that Sprint cares much whether you switch back to the Evo. They are in the business of selling expensive telecom service contracts, and the phones are just their bait to hook the suckers customers.

For my part, I have a 30-day trial with both the phone and the carrier. I switched from T-Mobile primarily over the GPS issue. If T-Mobile rolls out their GPS fix from Samsung this month on the Vibrant, without the new bugs introduced on the Epic, I might consider switching back. In any case, my trial window closes at the end of the month, and I am not crazy about keeping the Spint/Epic package unless I am confident that the new bugs will be fixed. The prudent thing to do would be to return the phone, cancel the contract, and wait.
[Epic 4G General] aero1:
I disagree. signal bars are generally problematic to use across devices, but signal DB is not, especially if you see corresponding poor performance. SNR is cosign from DB. Signal DB is in fact rported al over these forums as relevent by expert users. the company you reported criticizing GPS SNR may well have come under criticism for poor GPS attenuation.

The fact that in any given situation comparing several handsets at once, I see less sats in view and or in use with Epic, seriously implies that the slighlyt to moderately lower SNR values are relevant.

Are the 100% comparable? no. Have I found a way to log and average them like wecan on WM NMEA reporting? NO. is it per se damning of Epic? no. Is it part of the puzzle? I would argue that it quite possible is.

I think it is more likley Samsung's Galaxy GPS problems arrise from designing multipel variants not just of GSM and CDMA/EVDO but of GSM and CDMA in different countries with different carriers who may have different assistance systems. There is CDMA in East asia, and who knows what different specs those carrier asked for.

But I also think it is possible that there is slightly to moderately below average SNR performance from the hardware, and or multipath and other signal rejection in the chip (which may or may not be in that SNR) and trying to compensate (say with a overly sticky cache) may also be part of the problem.

I thinkteh SNR is a relevant and intersting thing to note, e ven though none of us would say it is the main problem
[Epic 4G General] aero1:
thank you for the data point. Are you experiencing any failure to lock, say especially after using gps, turning off the applciaiton (but not turnign off phone) and going back to a gps application 8 hours later or the next day?

about 4 hrs. almanac values are longer.
[Epic 4G General] dondadah88:
I had a problem with my gps only one time and a quick reboot solved it.

Im not sire if there is a problem messing with the gps or what is it.