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    Votes: 42 26.3%
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  • Total voters
    160

What concerns me about the GPS on the SGS is the wildly varying SNR readings. I see mine vary by 10-15 on each satellite even in locations where external background noise should be relatively low, which pretty quickly explains why it has trouble locking on to, or staying locked on to, a signal. I can use a similar device in the same location and the variation is only 3-6. It’s a simplification but that kind of suggests that most of the noise is coming from other circuits on the device itself and is of a periodic nature.


It's not just the GPS signal that bounces around. It's wifi and 3G/cell also. I have a wifi monitor app installed to prove what thought I was seeing, and the signal randomly gets better and worse with the phone in a fixed un-held position. You can see the same behaviour in signal level if you monitor the phone status screen for your cellular dbm while the phone is in a fixed position.

Numerous people have exhibited their bars "bouncing up and down" and the wifi signal indicator doing the same.

Would not all the signal discrepancies point to some kind of antenna issue or noise/interference issue? Your point about capacitors for instance also explains why exchanging a phone with no or very poor signal sometimes you get a new one that "just works". For instance my first phone couldn't talk to any cell towers at all and only got -100dbm when placed literally on top of a microcell. A replacement one worked so-so with signal bouncing around +/-50. My newest one only swings back and forth +/-25 which is good enough to actually get something done with (but still should be better since it freaks out my wifi!)
 
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In general, the following strategies are used to minimize the cold start in GPS systems
1. Reduce execution time by using domain knowledge
Need specialized post-processing techniques for
handling low and various SNR. BCM4571 is also a highly sensitive GPS chip for mobile devices based on the product brochure. Thus, the chip may pick up the signals and also noise. It is up to the driver how to process it.

It's highly unlikely that the driver on the Samsung is leaving the chip to 'pick up signals and also noise' and then process the raw data itself, that's a really significant computational overhead..which the gps chip is much better designed to handle itself.

I think the point here is that the chip itself is going to have trouble locking and maintaining sync if SNR is bouncing around to the degree that the readings indicate, and if it can't do that it can't give the driver much information about anything other than 'I can't see the signal reliably' As the signal power remains relatively constant unless you have wildy varying atmospheric conditions (not likely as the whole basis of Differential GPS is that in a local area it doesn't) that means the perceived noise must be fluctuating wildly, and that's a tricky thing for any receiver circuit to handle for all sorts of reasons that I won't go into here.

Most of these GPS devices can be put into a completely autonomous mode where they auto-initialise, track and re-sync themselves and just put out standard NMEA status messages over a serial link, the $GPGSA,A,3,04,05,,09 .... strings you may have seen in some debugs that contains satellite number, SNR etc etc in a big list. The 'driver software' then just basically turns it on and off and reports what it says. They're built this way of course so that they can be sold to someone making a simple USB GPS dongle or whatever and they have very little work to do to get a product out.

I can well believe that Samsung might have written a driver that tries for a little while to get a sensible status from the GPS chip and when it doesn't does all sorts of unneccessary 'resets' and 'cold-start' instructions but those SNR values come from the device itself and assuming the driver isn't arbitrarily changing them 'in transit' ..they don't look good to me.

Like I say, I really hope I'm wrong ..I'd like my Samsung GPS to work properly!..but I have an ominous feeling that unless the software fix does something really cunning, like switching other circuits off to reduce noise whilst a lock is being obtained.. and goodness knows what that would do to performance.. it's going to be some kind of fudge, rather like Apple's Iphone 4 signal strength bars..

An interesting discussion but pointless speculating further I guess as the 'fix' is promised to be out in September, so we'll see then and I'll sign off here with my fingers firmly crossed!
 
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I was browsing the market today and came across an app that would allow me to use my BT-359 external bluetooth GPS. Unfortunately that particluar app, "Bluetooth GPS" only worked inside the app. I thought, it would be great to use it for everything.

So after some more research I found a reference to an app called "Bluetooth GPS Mouse". The free version lets you try it, but at least now I know I can use my extremely accurate BT-359 until the final fix is released.

I am not sure about battery life since instead of using the internal GPS you have to use the bluetooth.
 
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I can well believe that Samsung might have written a driver that tries for a little while to get a sensible status from the GPS chip and when it doesn't does all sorts of unneccessary 'resets' and 'cold-start' instructions but those SNR values come from the device itself and assuming the driver isn't arbitrarily changing them 'in transit' ..they don't look good to me.

Thanks for your comments. I think that this is a fair conclusion

 
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edit: Also to the guy who enabled use wireless networks, like was explained before this lets the phone use the cell tower to get a rough position and then uses the phone's data connection to preload the gps almanac for that location. So then the almanac is stored for a while and that is why sometimes it will work even if you turn off the use wireless networks again.

This could be the case for using Broadcom location-based services when turning on wireless network.
See this GPS chip vender website:
Broadcom.com - Location-Based Services
 
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Just tried out GPS test on my EPIC.
GPS has been working fine for navigation in the car but I had no clue what it was actually doing.
Tried in 3 different areas on the way home.
In all cases, 9-11 IN VIEW, 3 IN USE and no matter where I am, a 98.4 foot accuracy...so my guess is that this # is burned into the phone by Samsung :)
This is actually very bad GPS performance (3 in use)
 
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This is a universal thread to discuss the GPS on the Samsung Captivate. If you are having trouble, need help or simply want to discuss the GPS this is the thread for it.

Please keep in mind the rules as well as the zero tolerance policy when posting.

All new GPS threads will be merged into this one.
 
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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.
 
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There's one Track I did. Pretty accurate.

Track 1 - Google Maps

When I used Google Nav it has been accurate. Not to mention 2-5 second reroutes when I drifted away from Google Nav directions. I know it's hard to believe, but it does work for some people.

If you zoom in, you ran off the road and drove on the sidewalk quite a bit. If you try this on something other then residential streets (highway) you will be really be surprised by how in-accurate it is.
 
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The point is, that compared to GPS on any other phone, this thing is way off. Did you cross the street to the median 5 times?

If you use Nav while driving it tries to reroute every few minutes because it thinks you are a parallel road or missed a turn. That is why people are complaining.

The level of accuracy you are happy with works fine if you are walking, but fails completely when driving.
 
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The point is, that compared to GPS on any other phone, this thing is way off. Did you cross the street to the median 5 times?

If you use Nav while driving it tries to reroute every few minutes because it thinks you are a parallel road or missed a turn. That is why people are complaining.

The level of accuracy you are happy with works fine if you are walking, but fails completely when driving.

I crossed the street a couple times to test it but you are right, it had me doing that more that I did.

Last weekend however I used Google Nav everywhere I drove. 100+ miles driving and it was spot on each time (actually, one exception was it plotted me on the road 5 feet to the left of me but quickly located me on the correct road).

For some, the GPS works adequately although still can be better. For other, it's completely broken. That's what I'm trying to say. It's not completely broken for all - so making posts stating the ones with a 'working' GPS aren't aware of the issues, don't know about GPS and so on aren't necessary.

I do hope they fully correct the issues however. As at some point, even the 'working' phones can become broken in terms of the GPS.
 
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Interesting issue. Frustrating for us all.:)

I'm in the camp of finding it hard to believe any will work correctlly 100% of the time (which myh oldphone does). That is because I went for 2 weeks, thinking "I must be lucky...mine is perfect). But I kept using it for everywhere I went just to be sure. And utlimately, it had me all over the place...exactly during a 50 mile trip when I was trying to show off the great Google Nav to my wife. :rolleyes:

So, I think possibly it takes the right combination of circumstances to witness the issue.

Until I see a high percentage of people that were having problems say it is now fixed, I'm having trouble believing it. Nothing personal aimed at anyone.

Gawd...I'm anxious for it to get fixed so I can get a Captivate again.
 
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I disagree about the comment about GPS devices working inside. If my wife's iphone can lock inside, the captivate should as well. Also, I can use my external bluetooth BT359 with my captivate and I can get locks all the time inside any building. I have tested that there is definitely a reception issue. I can put my hand on the top of the captivate and see the reception drop, and as soon as I remove my hand it works fine. For driving, if I place the phone behind the steering wheel, it seems to work just fine. But if I take a hold of it, I lose the GPS lock.

How did you get a firmware update? I never see anything and how do you know what version firmware you have?
 
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The firmware is beta - leaked from Samsung somehow - you have to use some developer tools to flash the new firmware. If you go into settings->about phone you will see the firmware version - shipping is i897UCJF6 - pay attention to the last two characters - the next to last is the month (F is 6th month - june - and 6 is a numeric build number). The latest Beta is JH7 - so it was built in August and is the 7th iteration)
 
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