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All things GPS

Is this a poll?

  • Yes, it looks like a poll.

    Votes: 42 26.3%

  • No, there is no way this is a poll.

    Votes: 31 19.4%

  • Why in the world is there a poll here?

    Votes: 87 54.4%
  • Total voters
    160
lordhamster said:
All phones use antennas. Covering the antenna on any phone will make the signal strength decrease. This is especially critical when talking about weak signals like GPS.

Despite what the Apple bashers tell you, no phone will work well if you cover it's antenna. The problem with iPhone 4 is not Covering the antenna, but rather touching certain points on the phone would essentially merge the two tuned antennae into one untuned antenna. Putting the antenna on the outside where people grasp it regularly when just holding the phone was the design problem. NOT the fact that blocking signal makes signal go down.
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I would agree, but I am not bashing apple, I am actually an iPhone fan, I was just mentioning the apple issue because it involved touching an area of the phone. I would also agree that a case will degrade the signal, however, with my iPhone 3GS, the GPS worked perfectly from my house and I always had a case on that. I am not a very technical guy, I was just wondering if the signal issue was something that could be fixed by an update of if this sounded more like a hardware issue
 
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!
 
Does resetting the GPS data in GPS Status clear the phone data or just the data GPS Status uses? In other words does this help all GPS programs or just GPS Status?

Sitting in the window GPS Test picks up and locks equal sats with or without the body glove case but the SNR drops about 3 points on average.
 
MSchaff30 said:
I would agree, but I am not bashing apple, I am actually an iPhone fan, I was just mentioning the apple issue because it involved touching an area of the phone. I would also agree that a case will degrade the signal, however, with my iPhone 3GS, the GPS worked perfectly from my house and I always had a case on that. I am not a very technical guy, I was just wondering if the signal issue was something that could be fixed by an update of if this sounded more like a hardware issue
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Most plastic or silicone cases should not be a problem at all. I really feel the samsung has some sort of firmware or driver issue. Of course until Samsung does something its a moot point anyway.

Provided your house isn't radio opaque, GPS does have a decent chance of working inside on the top floor. I know every type of GPS device I've had since 2001 has been able to get a lock on the top floor of my wooden house. Except for the captivate, which can't even get a lock from my driveway outside.
 
Thats good to know. That also follows along with what I have seen on the two captivates I have had. I didnt not follow this procedure, but did a more drastic step and used Odin to replace the ROM and also applied Cognition at a later point. Both times my GPS improved significantly.

All three situations (Rom replacements like I did and clearing GPS data as referenced here) accomplish what I was referring to im my original post. They clear whatever files are accessed frequently, written to, etc.

I feel more and more strongly as I read on this board and talk to others that this is relevant. Why else would GPS be great when you buy the device and degrade over time? the driver didnt change, the software didnt change...its all read only and yes they can cause erratic behavior. The files that are written to, updated, and change are certainly involved and seem to make a difference.
 
Or filesystem. Remember in terms of benchmarks the Galaxy S series uses an inferior I/O filesystem which its slower than most competitors (especially motorola). Perhaps it is the slower read/writes that is making the GPS readings crazy and/or slow...
 
DynaBlue said:
Interesting observation, Andyman10. I just turned on airplane mode, went outside and ran GPS Test. Within 30 seconds I had 8 in view, 5 sats in use. at 2:02 I had 11 in view, 7 in use. My SNR on the used sats was very steady at 33 up to an observed high (on this phone) of 41. I went back and turned off airplane mode and reaccessed GPS Test and it relocated all the sats within seconds but the SNR was back down in the 24-33 range on all in use sats. Might bear further testing.

Oh, and sitting at my desk which is right next to a window, about a 14" below the sill, I normally can't lock any sats though it will usually see about 2. With the airline mode turned off I saw and locked 8/5 almost immediately. Once airline mode was turned back on the phone still sees/uses 7/3 up to 8/6. Perhaps the answer is to go airline mode, lock your sats, then turn your Captivate into a phone again?

GPS Test seems to lose the sats and has to reaquire whenever you switch away from the app to something else, like the home screen, not just when the screen times out.
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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
 
That is possible, I would need to read up on that as Im kinda new to all this. I do think at least some of the problem or some peoples problem has to do with these files, the size they get to, something along those lines.
 
Lots of people report some improvement (but still seems slow time to fix from most reports compared to other modern GPS devices), but the poll shows ~38% see improvements, 35% see no improvement, 17% see things worse :

http://androidforums.com/samsung-captivate/182773-gps-after-update-same-better.html

It does seem the various firmware fixes allow the captivate to look at more satellites than before, but reading between the lines of all the data I've seen, I am more convinced than ever we are dealing with a bad GPS antenna and/or hardware receiver and Samsung is just attempting to play firmware games to mitigate that problem.

Maybe the *next* fix will properly address this issue, but to me it looks like we need some hardware changes like with the iPhone 4 to truly fix this. I hope I'm proven wrong, as IMHO this is the best phone out there at the moment ... EVO 4G could be if not for battery life/size, iPhone 4 could be if not for small screen and Apple lock in/limitations.:(
 
I have followed the steps in the OP however my phone is stuck in the "yellow downloading" mode. Odin never came up with a yellow box and I'm afraid to unplug my phone. Please tell me I didn't f@ck up my isht???
 
Rhiannon224 said:
I am glad to hear that someone has finally posed a rational hypothesis of the GPS problem and possibility of a fix in the future. For my needs it works fine, Google Maps is another story, I know my neighborhood very well and my location is within 20 meters or so of where I am but the map gives inncorrect directions. It says that a location is on the wrong side of the street. This makes me nuts, the GPS functions and Google Maps are wrong. I don't use GPS on the phone, if I want that I will buy a GPS.

Is there a better app for directions than Google's? I can sideload apps too so I don't care about AT&T's market ristriction.
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I haven't read through the entire thread yet, but one app that I downloaded is waze. It's fun...GPS and social networking/game at the same time.
 
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.
capturepul.jpg
 
well... my phone seems to be ok. However.... Oden didn't work for me. I followed the directions in order. I pulled the sim, put the battery back. Held the up/down buttons together. Oden was open, got the screen with the boxes and the start/master clear buttons. Plugged usb into phone while still holding up/down buttons (screen still black) and the gold digger came up.... Not a chick... the droid with the shovel. :)

And it stays there... No yellow box comes up in oden... nothing. SO... Before I try one-click or anything else I need to make sure I can flash back in case of emergency.

P.s. I'm running windows 7 64 bit
 
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