Can't use GPS w/o Data Connection?

Discussion in 'iPhone Tips, Help and Troubleshooting' started by WiiDSmoker, Nov 5, 2010.

  1. WiiDSmoker macrumors 65816

    WiiDSmoker

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    #1
    I have a old iPhone 3G loaded with Tom Tom USA on it. It does not have a data connection...but I'm not understanding why I can't use it?

    Every PND out there only has a GPS chip (like the iPhone 3G does); yet I'm unable to use it.

    What's the deal?
     
  2. r.j.s Moderator emeritus

    r.j.s

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  3. WiiDSmoker thread starter macrumors 65816

    WiiDSmoker

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    #3
    The Tom Tom app stores the maps on the phone.
     
  4. Applejuiced macrumors Westmere

    Applejuiced

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    #4
    It should work. What prob is it giving you?
    It's not hactivated right?
     
  5. r.j.s Moderator emeritus

    r.j.s

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    #5
    Oh, yeah, Tom Tom does ...

    I don't know then.
     
  6. bookwormsy macrumors 6502

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  7. trekkie604 macrumors 65816

    trekkie604

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    #7
    GPS won't work when Airplane Mode is on. I use my 3GS as a nav without the sim and Tomtom no problem as long as it's not in airplane mode.
     
  8. -aggie- macrumors P6

    -aggie-

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    #8
    That’s not true. You can be in airplane mode and then turn on location services, which will give you GPS access.
     
  9. trekkie604 macrumors 65816

    trekkie604

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    #9
    Does not work for me. I have just tried with my 3GS, Airplane Mode on, location services on - TomTom says Poor GPS Reception and just sits there (it isn't at the correct location), Google Maps says "Cannot Determine Location". Upon disabling Airplane Mode, TomTom locks my location in about 30 seconds.
     
  10. Carlanga macrumors 604

    Carlanga

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    #10
    tried it on my 3GS, doesn't work for me either w/out some time of data connection; my guess is the internet enabled features inside of tomtom are the culprit here...
     
  11. WiiDSmoker thread starter macrumors 65816

    WiiDSmoker

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    #11
    I'm thinking you're right. There's got to be a work around for this.
     
  12. David-fr macrumors 6502

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    #12
    Navigon works perfect
     
  13. Mlrollin91 macrumors G4

    Mlrollin91

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    #14
    Yep! Best app I've purchased!
     
  14. BadaBing!! macrumors 6502

    BadaBing!!

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  15. Airmark1 macrumors regular

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    #16
    Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_1 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8B117 Safari/6531.22.7)

    Did you say "No" to it asking you if Tom Tom could access your GPS data? If you did, I think that the location services could be ON and still keep GPS data away from Tom Tom. Make sure that the location services is ON amd the TOM TOM specific location services is ON.
     
  16. trekkie604 macrumors 65816

    trekkie604

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    #17
    Nono, it does work with no data connection (I.e. No sim inserted, wifi off); just not with airplane mode on.
     
  17. TheIguana macrumors 6502a

    TheIguana

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    #18
    The iPhone uses assisted GPS (AGPS). AGPS lets the iPhone cut location lock time by getting GPS satellite constellation data and the correct time from the cellular network.

    Without this information the phone needs to wait for the GPS satellites to transmit the data (taking about 12 minutes). This could explain why it is taking so long to get an accurate location lock. When you were trying to get a location lock was it out in the open with direct view of the sky (ala not behind glass or in a building)?
     
  18. Carlanga macrumors 604

    Carlanga

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    #19
    didn't try removing the sim, thanks, good to know if I ever have to use this scenario.
     
  19. Applejuiced macrumors Westmere

    Applejuiced

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    #20
    That makes sense.
    It probably needs a clear view to the sky and some time to lock in signal.
     
  20. pacohaas macrumors 6502a

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    #21
    I think there's either a bug in 4.2 or Apple decided that GPS radios don't interfere with airplanes because I just went on a trip this weekend and noticed that airplane mode no longer disables the GPS. If you run something like Loopt that uses GPS in the background, you can clearly see the GPS arrow is still active.
     
  21. itsmemuffins macrumors 68030

    itsmemuffins

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    #22
    Not true. I used my old 3G with Navigon without a data connection, get a lock within seconds.

    I now use my iP4 without a data connection and Navigon finds my location whilst indoors within seconds.
     
  22. coochiekuta macrumors 6502

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    #23
    your phone will not interfere with an airplane EVER. they will however interfere with cellphone towers. if you are in the air you have the potential to hit more than one cell tower at a time, causing them to reserve cellular channels for your phone. which could prevent others from making calls or dropping their calls.

    aircraft are highly advanced. a phone is not going to bring them down. :D
     
  23. TheIguana macrumors 6502a

    TheIguana

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    #24
    Your experience versus the original thread author could be explained at least partially by a few components of the iPhones core location service.

    One component of the location system in the iPhone is cellular triangulation. Cellular triangulation does not require an active data connection but it does require a sim card because it takes advantage of signal strength and data in the GSM standard. So even without cellular data the iPhone can use this to get a rough location estimate. This differs from assisted GPS where the assisted component does require an active data connection.

    Secondly, the GPS satellite constellation data and the correct time are really broken down into two parts, almanac data and the ephemeris data. Almanac data is a rough guide of the GPS constellation and is valid for days to weeks. Ephemeris is more accurate GPS constellation data and is valid for up to 2 hours in a specific location.

    So if an iPhone is cold booted or its location services have not been used in a number of days the system may be able to rely on the almanac data and cellular triangulation data to get a rough position. Then it can wait to receive the latest ephemeris data for the satellites above and use this to get a more accurate position lock. But because it already has almanac and cellular data to work with the system may be able to get an accurate lock in under 12.5 minutes versus the 12.5 minutes usually required to receive all of the almanac and ephemeris data.

    Both of these aspects could at least partially explain your quick time to position lock, contrast to the original thread author.
     
  24. kdarling macrumors demi-god

    kdarling

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    #25
    "Not ever" is too strong a phrase. Depends on the radios and interference location. Nothing is perfect.

    For instance, airline pilots have reported hearing the nasty "GSM buzz" of operating phones over their headsets, which can interfere with hearing ATC.

    If you read the anonymous NASA ASRS (Aviation Safety Reporting System) reports, there are instances where pilots have had problems with their instrument landing gear and/or autopilots, causing them to abort landings... and they traced the interference back to someone using their phone in first class. Made the passenger turn off the phone, and all was well again.
     

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