Tested and Proven gps fix for Samsung CaptivateTips


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  1. YellowGT0

    YellowGT0 Well-Known Member

    Did you sideload crack your phone njd911 if you did you need to do the CHMOD thing its in the sideload thread.

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  2. rajendra82

    rajendra82 Well-Known Member

    If you do go into the GPS testing software and do a position test, you will see that Captivate sees many satellites but chooses not to use them. Others devices reportedly use these satellites. This makes it hard to lock on to your position very quickly and accurately, which is why the GPS is slow and all jumpy at times. At certain times it may see 5 or 6 satellites but use none, which gives us the dreaded location unavailable error. This sounds to me like a software bug that can be resolved by a more liberal usage of the visible constellation of satellites, if it was a hardware issue it won't come and go like it does, at least I hope so.
  3. mi04se1

    mi04se1 Well-Known Member

    I tried the method above and stood outside in the open and had no luck. I did a master reset and when I got home I turned skyhook on a worked right away. I even tried turning skyhook on before I tried this method and it worked. Now it works indoors and outdoors, but Im not sure about accuracy yet.
  4. SuperAkuma

    SuperAkuma Well-Known Member

    It works fine for me now, thanks.
  5. JoelParke

    JoelParke New Member

    HI, I have attempted every fix as reported. The fixes helped some. Ultimately I returned the first phone for a replacement. The replacement was much better and locked relatively quickly. The problem is that while driving, the error range in Maps fluctuates a lot, enough so that while driving the phone repeatedly gives incorrect driving directions. I already have a Garmin that works well, but it's maps are somewhat in accurate.

    Samsung/At&t please fix this problem. I love the phone, but as a GPS it is a failure and is dangerous to use as a navigation aid.

    Does anyone else see it jumping from 5,10 meter accuracy to 100 m on a regular basis? Also at times it seems that LbsTestMode - Get Position Test might be better at holding a lock than GpsTest of Google Maps. Anyone else seen this behavior? THANKS
  6. tonyc

    tonyc Member

    Hi,
    I have done and experienced exact same thing as you..First unit never locks. Second unit locks (even though takes 5-10 mins sometimes), and fluctuates. I found that if I disable "use wireless networks" in locations setting, it jumps less often. I've tested it many times again, and it's almost usable now, with occasional error (ex., 5-10m fluctuations, where i end up on the local streets next to the freeway, and navigation re-routes).

  7. jmreed97

    jmreed97 Well-Known Member

    Most people are having this problem even after the fix... Make sure you call Samsung and get to a LEVEL 3 tech to report the problem. Also Call At&t to complain! I've spoke to 4 people at At&t and they all said this was the first they heard of the problem.
  8. jgcalderonperez

    jgcalderonperez Active Member

    Mine lock the location in about 3-5 secs with an accuracy of 300 meters. Better than nothing :-S
  9. BopDroid

    BopDroid New Member

    Before applying the changes:
    2-9 satellites found (no locks)
    76 seconds TTF
    400 meters accuracy
    Continued to search, never locked

    After the changes:
    9+ satellites found (3 locked)
    23 seconds TTF
    5 meters accuracy
    Locked.

    Now I would say that this is a hell of an improvement! Good enough for me until Samsung rolls out a fix.

    Note: Testing was done outdoors on a clear day in So Cal. Used the Test Position test from the GPS settings screen. Tested Google Maps and found location within a few seconds as well.
  10. benbald72

    benbald72 Member

    What seemed to work for me was to set the server and port to:
    http://supl.google.com

    Suddenly it can find my location in like under a second. I have SkyHook off and my WiFi is off, and I unchecked "use wireless networks" in the settings menu. The thing works splendtacularly. I can get it to work indoors and I could follow my movements very closely on Maps. It could track my movements within a small parking lot.

    LbsTestMode says it's accuracy fluctuates between 5 and 10 meters (does someone know if that's radius or diameter?). It's connected to 10 saellites with the CNo (does anyone know what that is?) at between 12 and 30 dBHz. Also, I'm not sure what the asterisks next to the satellites mean. Anyway, I did the GPS test in hot start mode and after 30 times with a 10 second interval it said "Average is 1358882 ms," I'm not sure what it meant, but the tests would each take less than two seconds, and some would even take less than one.

    Can anyone explain why this worked when the fix didn't work before? Does this trick work for anybody else?
  11. George0211

    George0211 Well-Known Member

    It shouldn't work. What you set your SUPL server to does not affect actual GPS, which works in accordance with the actual satellites. SUPL/A-GPS works off of cell towers and will only give you an approximate location. Depending on where you are, it could be anywhere between 1-3 mile radius, which is obviously isn't very accurate.
  12. benbald72

    benbald72 Member

    Okay, so now I have a better idea of what's going on. So this afternoon I turned off my GPS to save battery, and when I turned it back on the battery wouldn't work. I ended up changing it back to supl.google.com and it started working again. It seems like having the server changed resets it or something.
  13. benbald72

    benbald72 Member

    My understanding is that SUPL offers a database that the phone can use to compute its location by helping translate the information from the satellites. I understand that GPS works by the device measuring its distance from different satellites, but I guess the phone doesn't have every satellite memorized, so it has to look that up.

    At least, looking at how it behaves, and from my understanding of a brief skimming of the white paper (tl;dr) I'm guessing that's what it does.
  14. getDange

    getDange Well-Known Member

    SUPL is a plane info database that uses wireless triangulation for ASSISTING normal GPS function. SUPL has nothing to do with satellites. When your NORMAL GPS (satellite based) works fine, it finds your location quickly without SUPL. To find sat based location you lock on at least 3-4 sats, and each of the sats broadcasts ITS OWN geo position. Once the phone has that info from 3-4 sats, it can triangulate its own lat/long position and elevation. It does not need SUPL for this. What SUPL is used for in the phones is obtaining QUICKER lock by triangulating on wireless signals. So when you fire up Google Maps you would first get your position within 100-1000 meters from SUPL or Skyhook and then by the time you realize it is not precise enough, regular GPS already obtains its own lock and the phone shows your more exact position within 10 meters.
    Guys, I have to bed again, please before you claim you "fixed" your GPS, switch off wireless position assist in settings and only then see how many sats you lock on, and with what precision.

    Now I do know that there is a chance that the bug in SGS (hopefully software bug) CAN be related to SUPL, for example the software weighs SUPL info more than regular GPS info, or by mistake neglects regular GPS if SUPL is available, or tries to treat sat signals with SUPL algorithms by mistake, or whatever else can be messed up.

    Conclusion - let's wait for the Samsung fix. I do not think anyone can stumble upon a "fix" by themselves.
  15. benbald72

    benbald72 Member

    I do have "use wireless networks" turned off in the locations and security menu, and I have SkyHook turned off as well.
  16. benbald72

    benbald72 Member

    I already reported that a few posts ago. Here's some more detailed readings I'm getting right now (both SkyHook and Use Wireless Networks are turned off):

    TTFF/TTF: 6 seconds
    Accuracy: 5.0 meters
    Number of Satellites: 8

    Now, usually I have around that many satellites anyway, but it won't lock on a position, and none of them have asterisks after them.
  17. benbald72

    benbald72 Member

    From Broadcom's SUPL white paper (PDF download):

    Worldwide Reference Network
    The performance of a mobile AGPS device depends on the number of satellites
    included in the assistance data it receives. Broadcom’s Worldwide Reference
    Network (WWRN) is the leading source of such data in the mobile communications
    industry and has been a key factor in the commercial success of Broadcom’s AGPS
    Server products. The WWRN is a global network of reference stations that
    continuously tracks all GPS satellites and forwards their data to redundant Data
    Hubs. Real-time data for the entire GPS constellation is streamed from the Hub
    sites to all Broadcom SLP targets, enabling a single SLP to provide assistance data
    or compute positions for mobile GPS devices anywhere in the world. Connectivity to
    the WWRN is handled through VPN or SSH over the public Internet for developer
    evaluation, operator trials and limited commercial introductions, and through
    private frame relay for larger commercial systems. The WWRN is a pivotal resource
    for mobile location services that rely on AGPS, not only because it frees MNOs from
    the enormous task of having to develop, monitor, and maintain a GPS reference
    network, but also because it offers AGPS performance benefits that cannot be
    matched by a regional reference network. With data for all GPS satellites readily
    available through the Broadcom SLP, MNOs can focus on delivering LBS applications
    that take advantage of fast, accurate positions anytime and anywhere.

    LTO Data
    Building from GPS satellite data accumulated by the WWRN, Broadcom also offers
    Long Term Orbit (LTO) data products. LTO is a complete set of orbit data for all GPS
    satellites that is modeled in advance 5 and is valid for up to several days. This
    extended validity period is a powerful resource for global roaming because it makes
    out-of-network AGPS operation possible for days at time. For example, upon arrival
    at an airport after an international flight, users may have difficulty connecting to
    the regional wireless network to get access to positioning services. LTO provides
    GPS assistance data that is largely unaffected by gaps in wireless service.




    Like I said, SUPL provides a database of satellite locations. This is from page four of their white paper. If anybody reads the paper and disagrees with me, please let me know how you interpret it.
  18. George0211

    George0211 Well-Known Member

    Guys,

    Determining the current position of the GPS receiver is based on the distances of the receiver from the GPS satellites it's locked on to. Based on how far your phone is from at least 4 satellites, it figures out it's current location in 3 dimensions.
    This is why having SUPL or A-GPS will not give you a completely accurate position, unless you are standing very close to the cell towers.
  19. joesaito72

    joesaito72 New Member

    I've tried this fix on a number of occasions and every time it works great UNTIL the phone is rebooted. Once I reboot the phone, it doesn't work anymore.
  20. mongstradamus

    mongstradamus Well-Known Member

    I don't believe there is any fix that will work 100% time, will just have to patiently wait for an gps fix from samsung if it ever comes
  21. getDange

    getDange Well-Known Member

    Was not trying to sound rude, I apologize.
    Your numbers are very impressive, however I cannot reproduce them on my Captivate :( and that is the part that sux. So please forgive me losing my cool :)
    I wish Sammy released a fix that would not require me playing with settings, that is just not right. Again a gripe, I am sorry :)
  22. benbald72

    benbald72 Member

    So the phone's GPS receiver can determine how far the phone is from various satellites, but then the phone needs a way to determine where those satellites are in order to turn the distances into a location on Earth. This is where SUPL comes it, it offers a redundant database of the positions of GPS satellites in orbit.

    I guess other GPS devices either have this information stored in them or somehow get the information from the satellites themselves. Perhaps the problem is that the Captivate, for whatever reason, needs SUPL to determine where the satellites are, and the SUPL system on the phone is fussy. Hopefully the update will make it so the phone can determine its location even when it is not in range of any wireless network.
  23. George0211

    George0211 Well-Known Member

    The position of the satellite is part of the signal it sends to the receiver, along with a time-stamp, which says when the signal was sent. All GPS satellites send the signal at the same time. Based on that data and the fact that signal travels at speed of light, and knowing how long it took for the signal to get to your receiver, it can figure out where they are.

    Now, dude, think about this for a second. If all you needed is a connection to internet so you could connect to SUPL server, why would you need a GPS receiver in your device at all?

    SUPL server allows you to quickly figure out the general area where you are, because cell towers have GPS receivers on them.

    Also, those numbers alone don't mean anything on this device. I get 8-10 satellites as well and it says accuracy 5-10 meters. Problem is, it puts me no where near where I actually am. I stood in front of my house and it put me literally over 2 miles away on the map, while saying it was accurate to 5 meters.
  24. getDange

    getDange Well-Known Member

    ^^^ Thank you ! I could not personally prove that 5m accuracy is BS.
  25. NISMOFO

    NISMOFO Member

    I appreciate this post. It might not be a true fix, but any improvement is great. The first time I used NAV....I thought my phone had A.D.D.

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