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Tips GPS Fix - Dummies Guide

Discussion in 'Android Devices' started by ironass, Aug 30, 2013.

  1. aerismel

    aerismel Lurker
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    Thank you SOOO much for taking the time to reply...

    First, let me tell you that my phone is Galaxy s5 mini, not s4 mini. I don't know if this makes any difference but I wanted to say it just in case.

    I don't have any case on my phone, so that's not the issue. I USED TO have LLAMA installed but then I decided to restore my phone to factory settings and see if any installed apps were interferring with the gps functionality. It appears to have improved a bit, but just barely.. Sometimes it locks and doesn't lose the gps signal throughout all the trip, and sometimes it loses signal just as before. It's annoying.

    I will try turning everything off except GPS tools and MAPS and see how it works. And I will also try the app you suggested and see how it goes and I will come back and tell you what happened.

    However... I wanted to ask... The normal thing when being outdoors is to have a lock on most satellites?? For example, if the total satellites are 24 it should be normal to have pretty much all satellites locked on, right?? I'm guessing it's not a good sign that I have from 2-10 out of 20 after 10 minutes of being outside. Considering that all other phones from friends get connected in 1 to 5 seconds after opening google maps or waze... Considering that my phones doesn't lock on most satellites, could this be a sign that what is wrong is the phone itself???

    Thanks!!
     

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  2. EarlyMon

    EarlyMon The PearlyMon
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    No, the GPS constellation was originally 24 satellites flying in a half-geosynchronous orbit, rising and falling twice a day.

    You want 4 good satellites with a clear signal - any more, up to 6, increases your position resolution. More is interesting but irrelevant.

    Nowadays it's common to see more but there's no benefit to it.

    At no time can you see 24 satellites.

    If you could see the whole constellation from your hemisphere, the people on the other side of the world would be quite lost.
     
    #27 EarlyMon, Feb 10, 2015
    Last edited: Feb 10, 2015
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  3. aerismel

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    Thank you so much for your explanation. That makes me feel a bit more optimistic. Maybe thinking that it really is not a problem with my phone... If you have any kind of suggestion I will really appreciate it.

    Again, thanks!!
     
  4. EarlyMon

    EarlyMon The PearlyMon
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  5. aerismel

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    Ok, I will do that again and let you know if that works or makes it better. Thanks!!
     
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  6. Lorili

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    Hi,
    After i've tried everything except replacing my phone i found a nice solution here http://www.gps-fix.com/
    this is crazy but it's working for me...
     
  7. EarlyMon

    EarlyMon The PearlyMon
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    Aside from pimping Waze, that's only the partial solution @ironass and I already posted.
     
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  8. aerismel

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    Sorry for taking so long with this reply. I have tried all that we discussed before, and still doesn't work. I tried the Nokia Here maps and didn't work well.

    What is really weird is that sometimes (rarely) the gps gets a fix perfectly and it doesn't lose signal at all. That is very rare, but it happens a few, very few times. Could this be a hardware problem?? Or is it maybe something related to the GPS config file??? I have been following this thread as well: http://forum.xda-developers.com/galaxy-s5-mini/help/gps-issue-t2871145/page3#post59242348

    They say it is a hardware problem and sometimes when heating the phone on the left upper corner (seen from behind) it fixes the issue for a few days.

    I see that this is an issue with a lot of s5 mini devices.. Are there any other suggestions?? I'm willing to try anything.

    Please....

    Thanks a lot.
     
  9. aerismel

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  10. EarlyMon

    EarlyMon The PearlyMon
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    The heat fix is borderline crazy.

    If it responds to that, it's definitely hardware and the fix is likely to accelerate total failure.

    In any case, if you've done everything here with GPS Status and ironass advice, and a good skyview outdoors, and it's still not working, then it's very likely hardware.
     
  11. aerismel

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    Is there a way to perform a gps test on the phone?? I have read a lot about those secret codes for android. Here is a list of them: http://forum.xda-developers.com/showthread.php?p=52255264#post52255264
    There are codes to test gps:
    *#*#1575#*#* For advanced GPS test.
    *#*#1472365#*#* To Perform a quick GPS test.

    Those codes don't work on my s5 mini. Do you know why that is??

    Thanks!
     
  12. EarlyMon

    EarlyMon The PearlyMon
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    Let's be clear and take away the glamor.

    They're not secret codes, they're service codes.

    Now to your question -

    Yeah, they keep changing or removing those codes because contrary to Internet advice, more people have damaged their phones being inside service menus where they only thought they knew what it really did.

    If you want your phone tested, take it to a service center. They have the proper tools and you won't walk away with a paperweight.
     
  13. bobyong808

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  14. bidon

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    Hello
    You write "put your phone into Flight Mode so that the phone is only using its internal GPS for a fix".
    So does it mean that in S4 you can not switch off the A-GPS unless you are not in flight mode? When you just switch off mobile-data does it switch off A-GPS?
     
  15. ironass

    ironass Extreme Android User
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    Hello and welcome to Android Forums bidon :)

    If you require an accurate fix, then AGPS should always be left enabled. However, when setting up GPS Status and Toolbox it should be initially disabled to allow the phone's internal GPS to lock on to as many sat's as possible.
     
  16. bidon

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    I think you didn't understand my wuestion right. We were in international roaming and mobile-data in our S4 was switched off. But we used GPS and it worked fine. After that we saw that the phone actually recieved some data (3-5 kb sessions). So the question is: was that because of A-GPS was on? And can it be switched off (with standalone GPS on) not to get internet sessions in roaming?
     
  17. EarlyMon

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    Ummmm...

    I don't think so.
     
  18. Fernando Cordeiro

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    Tanks Ironass, it works for me, on my Motorola Moto X 2014 !
     
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  19. canonmaster

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    There seems to a lot of myths and mystic surrounding GPS. The US DOD put it up there and there 27 satellites in Low Earth Orbit (LEO) and the fly at about 22000km above the earth. 3 of the satellites are spares in case one fails or runs out of fuel and fall back to earth. The satellites are arranged in criss crossing orbit so that least 6 are always visible from any point on earth. Each satellite takes 12 hours to orbit the earth.
    The satellites have an atomic clock, costs about £20000, on board to keep time to the nearest nanosecond. As each satellite flies over the ground station in the US the clock gets updated so that ALL the satellites have the SAME time.
    Each satellite transmit a data stream that contains its satellite number, its clock time and an almanac that contains the position of it and all the other satellites in orbit.
    The GPS receiver ought to have an atomic clock but they are too bulky and expensive so it uses a quartz clock instead. The receiver picks a data stream from one satellite and by working out the time delay between the time in the data stream and its own time it can work out the clock delay. This represents the distance between the receiver and the satellite because the signal travel at approx. 1ns/foot. This means it is somewhere on a sphere whose radius is that distance
    By finding a second satellite it now knows it is somewhere on the circle where these two sheres intersect. Adding a third satellite put it on the intersection of three circles so it has a 2D fix. Adding a fourth sphere allows it to determine its location in 3 dimensions. With a bit of mathematical jiggery pokery the receiver can compute the error between its clock time and satellite time so its get an atomic clock for free.
    There are now some static GPS transmitters that know their location exactly so receivers can use this to get a more accurate fix. This is D-GPS.
    A-GPS is where receivers try to get additional data from local wifi and Bluetooth sources but they are not necessary and in any case are useless if your sitting on top of a mountain somewhere. Worse still if your the nosecone of a cruise missile.
     
  20. ExAviator

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    I place a coin on the ground and then do all the 'magic tricks' mentioned above to get the most precise GPS fix possible.
    To determine how accurate that GPS fix is I need to know the exact geographic position of that coin. (Above there are accuracy figures mentioned such as "within 10 feet".)
    My question is: how do you determine the precise geographic position of that coin to within a few inches as this would be necessary to determine a GPS accuracy of ten feet?
     
  21. ironass

    ironass Extreme Android User
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    As you can clearly see from the screenshots in post #1, the blue location dot is covering the trig point in an otherwise featureless field. Therefore, I knew that I was within 10ft of my position. You can use this with your own house if you know whereabouts in the garden you are standing. At the end of the day, this is a mobile phone that, when calibrated correctly, gives a fair GPS reading.
     
    #46 ironass, Dec 6, 2015
    Last edited: Dec 6, 2015
  22. ExAviator

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    On the Ordnance Survey web site there is a reference to the fact that because of the nineteen thirties technology employed it is possible for the position of a trig point to be incorrect by up to 20 metres. For those trig points designated as Passive points the accuracy is within a few centimetres but this has been determined utilising GPS.
    Ironass I'm sure what you have done is right and it is almost certain that your figure of 10 feet is correct.
    However, if the Trig point you used is not a passive point it is quite possible it could be some feet out. If it is a designated Passive Point, you may be determining S4 GPS accuracy against a datum measured by GPS albeit using a sophisticated methodology. Sorry I'm being rather pedantic! I'll go and get a glass of wine and relax!!!!!
     
  23. JerrySong1

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  24. AZgl1500

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    for those who are not aware of this tool, it is one that I think should be in everyone's GPS toolbox.
    Why? Because when you activate this app, it immediately polls a server to download the exact ephemeris table so the GPS Receiver "in the phone" knows which satellites to look for, and exactly where they are.... Bing! Bam! Blowy! thank you ma'am. It is dead on, almost "right now"...

    * GPS Status & Toolbox - Android Apps on Google Play

    The single biggest "hot item" to me on this app, is that if your phone has not been following the GPS satellites for a good long while, it can't know within a small degree of accuracy where you are.... ie, 3 meters, as opposed to 30 meters, or 300 meters.
    This app can reduce the Time To Accuracy delay to only a very few seconds, instead of waiting and waiting and waiting for the GPS Receiver to find "One Satellite" and then download the Ephemeris from that satellite.

    3 Satellites can give you a rough approximation, but having 12 to 20 satellites available can reduce the inaccuracy to almost inches.... but for us Civilians, we are not permitted to have access to that kind of accuracy.... we are allowed 3 meter accuracy though, and for the highways I travel, that is good enough.

    For those who have nothing else to do, here is some good reading:
    https://en.wikipedia.org/wiki/Ephemeris
     

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