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Thread: Can I use GPS functions on iPhone 3G without mobile phone subscription?

  1. #1
    Question Can I use GPS functions on iPhone 3G without mobile phone subscription?
    I'm thinking about buying a used iPhone 3G and not activating it with a wireless plan but simply using it as a GPS device (car navigation, geocaching, etc.). Will I be able to use its GPS capabilities without it being on a live mobile phone network?

    If so, anything special I need to do such as jailbreaking and/or unlocking? Is there a way to turn off the phone features while keeping on the GPS features to increase battery life?

    Any advice would be welcome. Thanks!

  2. #2
    Yes that would work, you donīt need an unlock or Jailbreak.
    The only thing i heard is that the iphone uses the gsm network in case the GPS has a bad connection, but i donīt know if its true. But anyway, there shouldnīt be any problems.

    You canīt turn of phone features completely but can turn off 3G and i think Edge, that should save some battery life.

  3. #3
    it needs to download maps on the go from a carrier or wifi. the carrier backup from the gps is just a way to guess by triangulating where you are, and really doesn't work IMO.

  4. #4
    Quote Originally Posted by ramicio View Post
    it needs to download maps on the go from a carrier or wifi. the carrier backup from the gps is just a way to guess by triangulating where you are, and really doesn't work IMO.
    Do you have any empirical evidence of this?

    AGPS /does/ help and it works quite well, as mandated by the FCC's e911 regulations.

    AGPS helps the iPhone (and any other AGPS enabled device for that matter) tremendously in two areas:

    -Start-up time. Have you ever seen how long it takes to start up a standard GPS receiver in an urban environment or indoors? It can take anywhere from 15 minutes to never if the GPS signals can't be locked on to. AGPS solves this by relaying current orbital configurations to your phone so it can lock on to the appropriate satellites quicker.
    -Location awareness and computation. AGPS servers have tons of horsepower to take the weak GPS signal your phone is receiving and compare it to it's own known coordinates and quickly determine your location. The most modern implementations also can use a hybrid technique that involves multi-cell triangulations as well.

    --

    Anyway as for the OP's question, theoretically I don't see any reason this wouldn't work. As others have mentioned some apps require a cellular data network to download maps unless you end up buying something like Navigon or RoadMate. You will also suffer performance losses as mentioned above because the iPhone wasn't designed to operate strictly as GPS, it is in fact an APGS device. The GPS radio in the iPhone is the single largest battery drain to begin with anyway.

    If you go through with it I'd recommend jailbreaking and then head over to the File Modding forums here for instructions on removing all unnecessary launchdeamons for your needs.

  5. #5
    Yes, by the fact that when I get no real GPS signal, and it relies on the cell towers, it locates me NOWHERE near where I actually am! How can you expect something to be as accurate in locating you by the speed of light, when it's only miles from you, versus satellites that are 12,500 miles above the surface. Something farther like a satellite that can measure an obvious delay will work much better when it has signal than a small, few square-mile area of towers trying to work it out.

  6. #6
    I do agree that multi-cell triangulation, when used by itself, is not an effective method of determining location, especially if you are moving (ie in a car). That wasn't my point though. Please at least try to have an understanding of the technology and how it works before trashing it.

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