iPhone 3G - GPS where there is no cell service?

Discussion in 'iPhone' started by The General, Jun 22, 2008.

  1. The General macrumors 601

    Jul 7, 2006
    Will it work? I don't quite understand assisted GPS. Does it NEED to be assisted? If I am on a hike and taking photos where there is no cell coverage or whatever, will it still be able to geotag my photos? How will that work?
  2. atszyman macrumors 68020


    Sep 16, 2003
    The Dallas 'burbs
    As long as you can get reception for the GPS satellites you should be able to geotag your photos without a problem. However that does bring up an interesting question about the maps. If it's using Google maps and you don't have cell service where you are, are you then mapless?
  3. nickspohn macrumors 68040


    Jun 9, 2007
    You will indeed be able to use the GPS even when there is no service. Assisted GPS is just help from the cell towers for quicker results.

    That's why with normal GPS devices you don't pay a monthly service.
  4. gloss macrumors 601


    May 9, 2006
    You'll be able to Geotag fine, as that only requires coordinates from the GPS chip. Now, navigation, on the other hand...
  5. JML42691 macrumors 68020


    Oct 24, 2007
    Geotagging should work, but I do not see how it would be possible to get map directions if there is not map info to load.
  6. MSD401 macrumors 6502


    Oct 18, 2006
    Ogden, UT
    hopefully a third party app ...aka tomtom would come with downloaded maps... thus making the gps work when out of cell coverage
  7. The General thread starter macrumors 601

    Jul 7, 2006
    Well obviously it won't be able to load the maps without an internet connection. It would be nice, though, if it could still track a line of where I've been when hiking. I used to have a GPS unit with no maps at all, but it would draw a line where I walk. Maybe there will be a program like this on the App Store!

    Is GPS tracking like that possible without cell service though? I guess I just don't understand what information it will be getting from the cell towers. That's the part I don't get.
  8. admanimal macrumors 68040

    Apr 22, 2005
    When a GPS device is turned on, it has to do some work to determine which satellites are available based on its current location. This is why it usually takes a few minutes for an unassisted GPS device to start up. With A-GPS, the satellite info can be looked up from a database over the cell connection, which it also uses to get a first estimate of its current location. However, the GPS can still work without any of this, just more slowly and sometimes less accurately.
  9. LoneWolf121188 macrumors 6502a

    Jun 7, 2007
    Longmont, CO
    Unless the maps were pre-loaded. Say you were going hiking somewhere remote, ie, without cell service. Load up an NSGS topo map with embedded coordinates and you're good to go.

    ...assuming an app is released to support this (I'd be surprised if one wasn't).
  10. 2002cbr600f4i macrumors 6502

    Jun 21, 2008
    Right, Normal GPS (like from a TomTom) has a chip that picks up radio signals from the costellation of sats and does triangulation from them to determine position. When doing this for the first time since turning the device on it can sometimes take several minutes to perform (but usually is very quick afterwards), and can usually get fixes to within 10 meters or so.

    AGPS (assisted) which is what the 3G iPhone does, will use a combination of the cell tower/Wifi location detection (like the older iPhone uses) to get a initial general fix while the GPS receiver chip is doing that initial long signal retrieval from the Sats. After the GPS chip gets the fix, it will update what's coming from the Cell/Wifi fix and get you much much more accurate position info.

    The advantage of having a dual system like this is that GPS doesn't work in-doors, where the cell/wifi method does, and the GPS can take longer initially, but once it's got it's fix it will be much more accurate.

    So, the older iPhone's cell/wifi-only positioning might get you a fix within a city block... the 3G will get you within 30 ft, it'll just take longer to refine the position...

    And remember, MAPPING and POSITIONING are 2 different things... the iPhone does positioning (Lat/Long info), but it needs the network in order to push that info into Google Maps and pull back down a map of that area. Unless somethign like the announced TomTom app allows you to pre-download and store maps of the area you plan to be in, you'll have no way to display your AGPS determined position on a map without the network.
  11. t0mat0 macrumors 603


    Aug 29, 2006
    I think it pays to also wait on judgement on the type of chip and also usage of the A-GPS chip by Apple. Google Maps doesn't necessarily in the future need to have network coverage to work. Offline Google Maps capabilities are presumably coming fairly soon, and Google Maps does cache its map data, as your previous map can be shown the next time you use Maps, even if you're out of network reception afaik. It doesn't take much to either precache a route's map data, or push GPS data onto a preloaded map on another application such as TomTom.
    Seeing as Google will be pushing this with Android (see the I/O conference videos on Maps on a rival touch phone), i'd expect it soon. I'd also expect a compass in the 3G iPhone.
  12. kdarling macrumors demi-god


    Jun 9, 2007
    First university coding class = 47 years ago
    A-GPS means the phone asks carrier servers for information on what satellites are in view and what their orbits are like (they're going like 10,000 miles an hour and are influenced by the sun and moon's gravity as well as earth's).

    This up to date information is the main assistance in getting a first fix within seconds.

    According to the Apple website, the original WiFi / cell tower methods are only used if the GPS fails.
  13. The General thread starter macrumors 601

    Jul 7, 2006
    Cool! Sounds like A-GPS is actually better than regular GPS, then.
  14. Jestered macrumors 6502

    Oct 13, 2005
    Austin, Texas
    That's actually not true. I have TomTom on my Palm and use it with a Bluetooth GPS receiver. My GPS receiver can pickup my location perfectly fine on the first floor, in the middle of a two story home. Old GPS couldn't do this, but recent (within the past few years) receivers don't have a problem with picking up indoor signals.
  15. DreamPod macrumors 65816


    Mar 15, 2008
    If you're lucky. An iPhone at work thinks I'm a couple miles away...
  16. geekmommy4 macrumors 6502


    Feb 10, 2008
    Yes, my iPhone was between 3 and 6 miles off from my home. Really weird, considering I'm in a major city and have great cell coverage. It'll be interesting to see what the new iPhone does when I turn the GPS on from home. Will it show me 3 miles away at first and then correct once the GPS locks in? (I know we don't know...it's just a theoretical question. LOL)
  17. j26 macrumors 65832


    Mar 30, 2005
    I tried that on Google Maps on my N95 and that's exactly what happens - it found me to within a mile and then a few seconds later pinpointed my position.
  18. Loonytik macrumors 6502a


    Jun 2, 2008
    Without a third party application the 3G Iphone isn't going to work like traditional GPS. Just look at the demo at WWDC, its not the same.

    Even with a third party app I just dont think it will replace my handheld Garmin for hiking or my Garmin GPS in my car.

    Besides, whats the point of hiking if you are taking your phone? Unplug my friend.....unplug. The matrix has you.
  19. edmartin macrumors member

    Jul 23, 2007
    Amen! But speculation is fun, and you bring up some interesting thoughts.

    Let's take the current Google Maps app. What major pieces is it "missing" compared to a dedicated GPS device like TomTom or Garmin (I know there are many more features of TomTom and Garmin devices so apologies for not including all but I'm just trying to look at the basics that would get the iPhone 3G to talk/route me from "point A" to "point B"):
    - Real-time, turn by turn directions
    - "Downloaded" maps (and other data)
    - Voice

    Adding all of the above would be relatively simple enhancements to Google Maps.

    - Turn by turn directions is "simply" a matter of live location update against the routing from point A to point B that you can already do.

    - Downloading or pre-caching maps is a "simple" matter of pre-loading the maps you'd need in your point A to point B route/plan; "Do you want me to pre-load your maps for this route in case you go out of cell phone range on your trip Yes/No?". Like you said, Google Maps already caches the current/last map.

    - Voice is probably the "hardest" but then again, that is pretty simple technology; in other words, it's a matter of downloading voice clips that get stitched together into directions or going the robo-voice route and using the tech to "translate" text to speech.

    The current dynamic between Google & Apple is interesting and perhaps different than when the 1st gen iPhone was coming out. But Google could no doubt make a nice chunk of money by beefing up Google Maps for use on the iPhone, Andriod and all other mobile devices.
  20. LoneWolf121188 macrumors 6502a

    Jun 7, 2007
    Longmont, CO
    ^^ There's two ways that come to mind to do voice: one is to attach a voice tag to every road name, so that when the map gets downloaded, the corresponding voice clip gets downloaded too. The other way is to just use a synthetic speech generator that "reads" the road name on the fly (phonetically). The latter method wouldn't use voice clips.

    So is the earth. ;) If I'm not mistaken, GPS satellites are in geosynchronous orbits. Meaning the number of satellites in view depend on where you are on the earth, not which ones happen to be overhead when you power on your GPS radio.

    Well, I'd hope so, considering the "A" stands for "Assisted"...I'd hope Assisted GPS would be better than regular GPS. ;)
  21. adamerr macrumors 6502a


    Jun 7, 2008
    do you think TomTom will release their maps for the iPhone anytime soon?

    just so we dont have to keep using google maps.
  22. GotMac? macrumors member


    Jun 12, 2008
    Another possibility, what if Google decides to leave Apple and make their maps only exclusive to an android device? Does this then mean the Tom Tom app is more a reality?

    I do not see Google supporting Apple once Android releases, but then again that's just my weird feeling about that.
  23. daveschroeder macrumors 6502

    Sep 14, 2003
    Madison, WI
    Guys...let's not jump to conclusions:

    Some A-GPS solutions require an active connection to a cell phone (or other data) network to function, in others it simply makes positioning faster and more accurate, but is not required.

    We don't know how Apple has implemented A-GPS yet.

    Also, from the iPhone SDK license agreement:

    "Applications may not be designed or marketed for real time route guidance [...]"

    Further, Apple previously had a video demo of Maps with GPS here, which showed what looked like turn-by-turn guidance in Google Maps, and it has now been removed (every other "feature" on the left sidebar still has a demo video).

    So I don't think we can jump to conclusions about what the A-GPS functionality in the iPhone can or can't do, as we'll be limited by its practical implementation:

    — It may or may not be able to use GPS without any cell signal. If Apple's strategy for GPS in the iPhone revolves exclusively around applications which require an internet connection, Apple's A-GPS implementation may require a cell signal. I am fully aware it is technically possible to NOT require a cell signal; what I am saying is that we can't yet jump to that conclusion.

    — Apple, as the gateway for all applications, has prohibited "real time route guidance". This could be for a variety of reasons, not the least of which is that while an always-on unlimited data connection is great, there are a number of practical and business reasons this may have been decided against, at least for now, by Apple, AT&T, or both. Or, could it be that Google wishes to provide this functionality in Maps? If so, why has the video, showing what was essentially that, been removed?

    While I'd love for this to be able to store map data locally, be used as a substitute for a dedicated GPS unit when hiking, be used as an in-car, portable nav system with — finally — a good interface, I don't think we can make any of those conclusions with any certainty. Apple is focusing on Location-Based Service, not traditional GPS functionality.

    I hope I'm wrong and that we'll see a whole slew of other apps for hiking and traditional navigation.

    (And to the person who thinks the iPhone will have an electronic compass? Keep dreaming. We'll be lucky if the iPhone 3G supports GPS without a cell signal, and even then, if it will be able to get a GPS fix in any reasonable amount of time without a cell signal. Cell phones don't have the satellite antennas that dedicated GPS units do, and some of those can take quite a while. Also, A-GPS doesn't "look up satellite info over the cell network" or whatever it was that someone said above. Might want to do a little more reading about it. Yes, it speeds things up, but a conventional GPS fix is still required for GPS accuracy.)
  24. kdarling macrumors demi-god


    Jun 9, 2007
    First university coding class = 47 years ago
    Semisynchronous. Orbits once about every 12 hours.

    They'll probably never say. We'll have to use empirical evidence.

    If they're really using the Broadcom chip, then they were supplied with sample code for several modes, including their neat Long Term Orbit enhancement, which is like getting assistance for autonomous operation.
    I think that it's the map suppliers in control of that. TomTom owns TeleAtlas, which Google uses for mobile maps. Nokia owns NavTeq, which is the web map source. It's surprising that Google didn't bid for maps themselves. Which means that maybe they're working on their own?
  25. rayward macrumors 68000

    Mar 13, 2007
    Houston, TX
    Here's hoping the TomTom app is for real. Running both the GPS and 3G chips for navigating is going to kill the battery in about 5 minutes and possibly set the unit on fire.

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