GPS on 3GS works without cell coverage

Discussion in 'iPhone' started by firewood, Sep 20, 2009.

  1. firewood macrumors 604

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    #1
    Just wait long enough.

    Tried it on a hike deep into a National Park between mountain ranges recently. In Airplane mode, the GPS didn't get a location. But with Airplane mode off (but no cell signal obviously), the iPhone finally got a good Location after sitting for about 5 minutes in a meadow out from under the tree cover (had to tap the blue circle on the Maps app several times). The GPS coordinate (from the Compass app) was less than 25 meters off from my friend's expensive Garmin hiker unit.

    The Maps app had also cached a wide-area map downloaded on the drive to the park, so when zoomed way out, it showed a blue dot over a very blurry map image of part of the park.

    ymmv.
     
  2. crpercodani macrumors member

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    Sep 18, 2009
    #2
    The GPS on my 3G has always worked without service, heck even without a SIM card. I use Navigon quite often (actually sold my Mio GPS since the iphone does that and tons more) and it gets satellite locks in about 30 seconds when I have it on a windshield mount. When I'm out in the woods on my 400ex it takes around 1-2 mins under tree cover. I barely notice a difference with or without a SIM.
     
  3. jav6454 macrumors P6

    jav6454

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    #3
    Yes it has happened to me also. Takes me from 2-3 min (depends how many satellites are available).
     
  4. aphexacid macrumors 6502a

    aphexacid

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    #4
    Its supposed to work without cellular service. You're not going to get agps, assisted gps that gives you a super quick fix. But you will eventually get a fix.

    I dont know why it didnt work in airplane mode, unless it shuts down everysingle thing from cell radio to wifi to even gps.
     
  5. trainguy77 macrumors 68040

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    #5
    Yeah airplane modes seems to turn off GPS as well.
     
  6. Interstella5555 macrumors 603

    Interstella5555

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    #6
    As others have said, the GPS works independently of the cell service, but does require a cell connection to load map data in most cases. If you had a map loaded then lost coverage and are looking at the same area you should be fine, but at some point the map data is purged in the Maps App and you'll just get a gray background with the blue dot. I'm assuming if you have the Tom Tom app this wouldn't be the case though.
     
  7. -aggie- macrumors P6

    -aggie-

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    #7
    Yes, if you have Tom Tom, you'll have the maps, so you don't need an internet connection for maps.

    Airplane mode turns off GPS, but you can turn it right back on independent of being in airplane mode. Try it.
     
  8. trainguy77 macrumors 68040

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    Nov 13, 2003
    #8
    Same goes for navigon and most of the other turn by turn apps.

    How do you turn GPS back on by the way? I don't think it can be done.
     
  9. -aggie- macrumors P6

    -aggie-

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    #9
    Turn on airplane mode. Then go to location services and turn it on. Understand?
     
  10. X5-452 macrumors 6502

    X5-452

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    #10
    I was on vacation in NYC a month or two ago and pre-downloaded detailed maps of all 5 boroughs. Turned off data roaming and was able to GPS my party everywhere we went without problem. The key is to make sure you have the maps already cached or else you'll only see a pulsing blue dot on an empty grid.
     
  11. trainguy77 macrumors 68040

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    #11
    Airplane mode doesn't turn off location services.
     
  12. firewood thread starter macrumors 604

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    #12
    Have you verified this on an actual iPhone 3GS?

    (Do a fresh reboot and move far enough away from the last location to make sure there is no cached location in memory. Then try.)

    I tried for over 10 minutes and could not get any location in Airplane mode under an open sky view. I didn't try toggling the Location Services switch though, which stays on after switching to Airplane mode.

    Maybe the switch lies?
     
  13. -aggie- macrumors P6

    -aggie-

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    #13
    Sorry, it had been awhile since I tested this. Anyway, all you need to do is go to Maps and then click on the blue thingy in the left bottom corner.
     
  14. Jimmy James macrumors 68040

    Jimmy James

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    #14
    Newsflash: I discovered that my Garmin GPS also works without cell coverage

    ymmv
     
  15. jav6454 macrumors P6

    jav6454

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    #15
    Your post can be taken as either sarcastic or as a troll in progress.
     
  16. Jimmy James macrumors 68040

    Jimmy James

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    #16
    Pure sarcasm. A device with satellite GPS reception capabilities (such as an iPhone, such as a Garmin GPS) must be able to determine position from that source alone, or it is malfunctioning.

    I guess I find it humorous that a large percentage of Apple users seem to believe that GPS is a cellular service and an invention of Apple and/or AT&T.
     
  17. trainguy77 macrumors 68040

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    #17
    I just went and tested this. I can't get GPS to work when in airplane mode. First I turned on airplane mode then tried google maps by clicking the bottom left button. No luck. I tried Navigon. It just sits waiting for GPS signal. I then went and toggled the location services switch. Repeated the tests. Still nothing happened. I then turned off airplane mode and tried navigon it picked up signal in about 30 seconds. Earlier I waited minutes and no response from it.
     
  18. ob81 macrumors 65816

    ob81

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    #18
    This is good to know. I have never tried on 3G, ad I am not really in areas without coverage. 1 more reason to grab a 3gs though.
     
  19. firewood thread starter macrumors 604

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    #19
    It had better. GPS is the top bullet point on its features list, not the 5th or 6th. The Garmin also doesn't have 3 or 4 radio transmitters on the same circuit board partially jamming the satellite signal.

    But an iPhone with aGPS and a good 3G signal will lock a lot faster from a cold boot after being off overnight than a Garmin.

    Trade-offs.
     
  20. -aggie- macrumors P6

    -aggie-

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    #20
    Trust me it worked on OS 3.0.

    See these threads:

    http://forums.macrumors.com/showthread.php?t=736066&highlight=gps

    http://forums.macrumors.com/showthread.php?t=755113&highlight=gps

    I tried it yesterday, and it worked, however I had to get the maps first, which I never had to do before. Today, I tried it again, and it never found the satellites. I'm thinking that an "enhancement" of 3.1 has broken this somehow. I'm PMing one of the others in one of the threads I cited above to see if theirs still works in 3.1.
     
  21. soLoredd macrumors 6502a

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    #21
    So, if I am in Airplane Mode and on a flight, will the GPS work? Is it capable of tracking you? That would be pretty cool.

    I thought Airplane Mode shut off everything but I could be wrong.
     
  22. jcb10 macrumors regular

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    May 14, 2008
    #22
    Airplane mode shuts every transmitter/receiver down

    No, you were right. Airplane mode turns off every transmitter/receiver function (cell, wi-fi, Bluetooth, GPS) in order to meet FAA regulations.

    And let me add to the voices surprised at people who thought GPS wouldn't work without cell reception. Perhaps they're just confusing the Maps app with GPS functionality. I have dozens of geo-tagged photos taken with my 3G last year in the Australian Outback -- hundreds of miles from cell coverage -- that show up in my iPhoto's places function, for example.
     
  23. trainguy77 macrumors 68040

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    #23
    The second thread doesn't mention airplane mode. The first mentions it be no one confirms it works when in airplane mode.
     
  24. firewood thread starter macrumors 604

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    #24
    It takes so much longer for the iPhone aGPS to get a lock (if it doesn't already have a recent one) without any cellular or wifi connectivity, that most people give up and assume that the GPS doesn't work at all.

    With a Garmin, people are used to letting the unit "initialize" for a couple minutes after a cold start until it finally finds enough satellites.
     
  25. trainguy77 macrumors 68040

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    #25
    Actually aGPS doesn't even function without cell coverage. I find that it only takes about 30 seconds for GPS to work. If not less when I don't have cell coverage.
     

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