Is it normal for location to be a bit off?

Discussion in 'iPhone' started by Bathplug, Jan 21, 2013.

  1. macrumors 6502a

    Joined:
    Jul 12, 2010
    #1
    When I use apple maps it shows my location as slightly next door with a wrong house number. I've reported the problem a few times. I don't really mind as the pin is close enough but using apps like day one which is a journal app that adds location to your entries. It would be nice if it said my house address rather than a different house on the street.

    Google maps also shows my location as slightly next door with a different house number to what apple maps shows. Both are wrong anyway. I've waved the phone in a figure of eight in both maps apps and the compass apps to try and re calibrate my iphone but I still get the same results.

    Iirc my iphone 4 displayed my correct location but its never quite been the same on the iphone 5 even using the good maps app.
     
  2. macrumors 68020

    John T

    Joined:
    Mar 18, 2006
    Location:
    UK.
    #2
    Yes, this is quite normal. You can't expect a 'phone map app to be as accurate as a dedicated GPS which obtains its info from satellites.
     
  3. macrumors 603

    scaredpoet

    Joined:
    Apr 6, 2007
    #3
    Uhm, The GPS in the iPhone also get its info from satellites. The map data is retireved from the itnernet.

    That said, it's possible that the map imagery is slightly off, while the actual reported location itself is fine. In any case, yes this happens from time to time, and that's just one of the quirks of GPS vs map imagery.
     
  4. macrumors 6502a

    Joined:
    Sep 4, 2009
    Location:
    USA
    #4
    GPS satellite signal doesn't travel through buildings. It can only obtain when outdoors or very near a window.

    Is it possible that your last position outside before entering your house is slightly next door?
     
  5. macrumors 68020

    Joined:
    Apr 12, 2011
    #5
    Actually it does. I can get a very accurate location within 10 to 15 feet in my basement, at work, etc.
     
  6. macrumors 6502a

    Joined:
    Sep 4, 2009
    Location:
    USA
    #6
    A smartphone can use other means, such as cell towers and wifi, to triangulate its position. These methods work sometimes, other times not so much.

    But, to answer the question, it is generally not possible to acquire GPS satellite signal indoors, in dense wooded or urban areas, canyons, etc.
     
  7. TG1
    macrumors 6502a

    TG1

    Joined:
    Feb 21, 2011
    #7
    Having wifi on really helps to refine your position especially when indoors and downstairs.
     
  8. macrumors 601

    Joined:
    Jan 16, 2008
    Location:
    Bristol, UK
    #8
    IMO this is one of the biggest falsehoods perpetuated in the technology world.

    Yes, that's certainly the case if you're in a tall building and you're not very high up or where the building has a metallic roof of some sort, but in the average house or smaller office building I never have a problem getting a GPS signal on a smartphone or similar device.

    Perhaps it has something to do with differing construction standards and building types around the world...
     
  9. vastoholic, Jan 21, 2013
    Last edited: Jan 21, 2013

    macrumors 68000

    vastoholic

    Joined:
    Jan 28, 2009
    Location:
    Tulsa, OK
    #9
    If you have wifi enable, then you'll be fine. I don't have a problem either except for those places you mentioned. I remember though, I had a little Garmin ForeTrex 301 and I was in a guard tower made of thick cement and glass windows. I had to stick my arm out the window in order to acquire a satellite lock. So people are probably confusing that type of behavior with how mobile phones act these days.
     
  10. macrumors 6502a

    Joined:
    Sep 4, 2009
    Location:
    USA
    #10
    There is no falsehood. This is the way GPS has always been.

    Using my iPhone indoors (with no cell or wifi signal) the GPS Status app reports satellite fix is poor and horizontal accuracy is 165 meters.
     
  11. macrumors 601

    Joined:
    Mar 25, 2009
    Location:
    Lincoln, England
    #11
    Nah. Try using a sat nav indoors and not near a window and it will complain about weak/no signal (mine does at least).

    Phones usually have A-GPS (the iPhone does), which means they can use cell towers and WiFi to get position too, so when you open up maps indoors it's probably because you're connected to WiFi.
     
  12. macrumors 601

    Joined:
    Aug 27, 2012
    #12
    Doesn't civilian GPS have some margin of error?

    The military doesn't want you to build your own hell fire drones! :)


    Anywhoo, mine is perfect, it even pin points the exact part of the house am in! :D Actually that would be bad if I pissed sum1 off. :eek:
     
  13. macrumors 68020

    Joined:
    Apr 12, 2011
    #13
    Where I work there is no wifi, yet gps places me within 10 feet of my location. No cell tower triangulation will ever get me that close. In fact, with my old razr maxx, I could define what to use in finding my location. I would have it only use the satellite, and not cell phone or wifi. It would start out by saying finding satellites, and it did, and would locate me inside that building that had a metal roof and brick sides. So yes, gps works inside buildings.
     
  14. macrumors 68000

    vastoholic

    Joined:
    Jan 28, 2009
    Location:
    Tulsa, OK
    #14
    GPS on phones work inside buildings. Like I said, my Garmin ForeTrex 301 has to be able to see the sky for it to lock onto any Satellites. I'd have to go look at the tech specs on it to see what exact type of technology it uses compared to smart phones.
     
  15. macrumors 601

    Joined:
    Jan 16, 2008
    Location:
    Bristol, UK
    #15
    That's not what A-GPS is or does.
     
  16. macrumors 601

    Joined:
    Jan 16, 2008
    Location:
    Bristol, UK
    #16
    This is what I get indoors

    I'm not next to a window and (quite unusually) the roof of the house is also covered in snow.

    Perhaps I am getting a GLONASS signal - I don't really know enough about it to say whether it's better indoors or even if iOS lets Apps access the same sort of data from it.
     

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  17. macrumors 601

    Joined:
    Mar 25, 2009
    Location:
    Lincoln, England
    #17
    A-GPS uses cell tower triangulation/network information to find the closest satellite and get a faster lock on, but mobile phones often use other location services in tandem.

    Any modern phone that supports A-GPS will support location by network/wifi too.
     
  18. macrumors 601

    Joined:
    Jan 16, 2008
    Location:
    Bristol, UK
    #18
    That's not A-GPS

    https://en.wikipedia.org/wiki/A-GPS
     
  19. macrumors 601

    Joined:
    Mar 25, 2009
    Location:
    Lincoln, England
    #19
    ""Standalone" or "autonomous" GPS operation uses radio signals from satellites alone. A-GPS additionally uses network resources to locate and use the satellites in poor signal conditions. In very poor signal conditions, for example in a city, these signals may suffer multipath propagation where signals bounce off buildings, or are weakened by passing through atmospheric conditions, walls, or tree cover. When first turned on in these conditions, some standalone GPS navigation devices may not be able to fix a position due to the fragmentary signal, rendering them unable to function until a clearer signal can be received continuously for a long enough period of time. A fix may take as long as 12.5 minutes (the time needed to download the GPS almanac and ephemeris).[2]

    An assisted GPS system can address these problems by using data available from a network. For billing purposes, network providers often count this as a data access, which can cost money depending on the plan.[3]

    Assistance falls into two categories:

    Information used to acquire satellites more quickly [Mobile Station Based(MSB)]
    It can supply orbital data or almanac for the GPS satellites to the GPS receiver, enabling the GPS receiver to lock to the satellites more rapidly in some cases.
    The network can provide precise time.
    Calculation of position by the server using information from the GPS receiver [Mobile Station Assisted(MSA)]
    The device captures a snapshot of the GPS signal, with approximate time, for the server to later process into a position.
    The assistance server has a good satellite signal, and plentiful computation power, so it can compare fragmentary signals relayed to it.
    Accurate, surveyed coordinates for the cell site towers allow better knowledge of local ionospheric conditions and other conditions affecting the GPS signal than the GPS receiver alone, enabling more precise calculation of position."

    Pretty much what I said :p it uses information from cell towers to obtain a better lock on a satellite.
     
  20. macrumors 601

    Joined:
    Jan 16, 2008
    Location:
    Bristol, UK
    #20
    No, it connects to an A-GPS server (i.e. over the internet).

    The A-GPS server provides data that makes the GPS lock faster.

    The only link to "cell towers" is that your mobile data will obviously run through them.

    Theoretically, A-GPS could work with a Wi-Fi or wired connection - but whether it does or not would depend on the type of device you are using.
     
  21. macrumors 601

    Joined:
    Mar 25, 2009
    Location:
    Lincoln, England
    #21
    Fair enough; I was a bit confused about how it works.

    However the entire point was that its unlikely that the phone will be using GPS (or A-GPS) indoors to get a location fix, it's more likely to be using wifi and cell tower triangulation; which almost all modern smartphones are capable of doing.
     
  22. macrumors 6502

    Joined:
    Jan 20, 2012
    Location:
    LL22, UK
    #22
    what you all forget is what happens if i move my router ;)
     
  23. macrumors 65816

    Joined:
    Jul 29, 2012
    Location:
    Singapore
    #23
    My iPhone always shows my location to be across the street where I live :(

    Sometimes it's accurate though.
     
  24. macrumors 6502a

    Joined:
    Sep 4, 2009
    Location:
    USA
    #24
    I see you also have cell signal, and that could be why.

    In the attached screenshot, I'm indoors with no service.
     

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  25. macrumors 601

    Joined:
    Jan 16, 2008
    Location:
    Bristol, UK
    #25
    How?

    My cellular provider does not know where I am to 10m accuracy.
     

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