5 ms·

Isn't this because the GPS on the iPhone is assisted and not true?

• cheald 16y ago
  The original iPhone had only assisted GPS. The 3G and 3GS have both assisted and true GPS.
  • lwhi 16y ago
    The difference between the two is pretty stark. Could true GPS have been turned off?
    • cheald 16y ago
      I was thinking that, too, but I'd presume that an app designed specifically to do GPS measurements like that (for use in plotting a pedestrian route) would be using true GPS, since you have to be moving pretty quickly (like, traveling in a car) for assisted GPS to be useful. Additionally, on the Motion-X website, they say that Motion-X doesn't work on the original iPhone or the iPhone 2G, because it doesn't have the necessary hardware to get a true GPS signal. While it is entirely possible that true GPS was turned off (it'd be great if the author could verify/retest if needed!), I'm somewhat doubtful that those tests were done with only cell tower position estimations.
      • lokshin 16y ago
        True GPS was definitely turned on. Motion X doesn't tell you how many satellites it's tracking, but handy runner was tracking 6 at the time (iPhone4 vs N1), and MotionX was showing an acquired signal so it must have been tracking at least three. I also tried to hold the phone as loosely as possible (although I doubt this made a difference). There is a comment above on Apple choosing a lower sampling rate in exchange for better battery life. I think this is probably right on. Most users will only be using the GPS to mark driving directions or to record something like running. In these cases the GPS is definitely good enough (you're just hugging streets anyway). Unfortunately, it's not good enough for me : ). I would definitely be more than willing to run more tests or try different programs if people throw out ideas.
        • cheald 16y ago
          Not exactly on-topic, but can you share what you're working on that needs that kind of accuracy? I'm awfully curious. :)
        • lwhi 16y ago
          It's a shame .. if functionality is going to converge into one device, I think it's important that the individual functions aren't limited.
          • cheald 16y ago
            Honestly, I think that's Apple being Apple. Cutting GPS quality means better reviews and a better user perception. No reviewer is going to write "Yeah, my GPS was only accurate to 14 feet", but you can be damned sure that every reviewer is going to write about the battery lifetime under normal usage conditions (including GPS). I'm not meaning to suggest that stacking reviews is the only purpose behind it - if it doesn't affect the user experience, then the battery savings is justified - but it is typical Apple. By way of another example, their approach to being caught with their hands in the signal cookie jar with regards to the iPhone 4 signal problems (specifically, how they manipulated the bar calculation algorithms to show a stronger connection than other devices for a given signal level)? No worries, we'll fix that, but we'll make bars 1-3 taller so that psychologically, you feel like your signal is better. Apple is masterful at manipulating what people see to get them to believe that they're getting the best possible experience, but the laws of physics dictate that they have to cheat somewhere sometimes. I don't mean that to sound perjorative, but just to point out that part of Apple's ability to do user experience so well is their ability to manipulate the user into thinking the positive things they want them to.
            • lwhi 16y ago
              I think the best way to deal with this is to offer choice - fine-grained GPS (+ associated battery cost) if the user chooses it; but I suppose that isn't the Apple way ...
              • 16y ago
  • tzs 16y ago
    The original iPhone did NOT have GPS at all. It had cell tower triangulation and Skyhook. Assisted GPS is a superset of GPS using other technology to assist GPS by doing things such as getting almanac data from a server instead of from the satellites or getting the time and approximate location which allows faster computation of position from the satellites, or offloading some of the computation to a server.
    • cheald 16y ago
      I'm suffering from confusion of terms. Folks have been referring to cell tower triangulation as "assisted GPS" in relation to cell phones, and the term has become somewhat muddled. It's not A-GPS as we have in modern hardware, but people tend to use the term "assisted GPS" to refer to cell triangulation/Skyhook systems.
• chaosmachine 16y ago
  Assisted GPS is superior to normal GPS. It's true GPS plus faster acquisition via cell towers. http://en.wikipedia.org/wiki/Assisted_GPS http://en.wikipedia.org/wiki/Assisted_GPS
  • deleted 16y ago
    [deleted]
  • nimrody 16y ago
    It's better if you have cellular reception (and sometimes you need your carrier to enable that feature for you). Unfortunately, if you are using non-assisted GPS on these newer phones, you get poor performance. They were designed for AGPS and lack the necessary hardware that dedicated GPS units use. Poor performance meaning usually very long acquisition time and less accurate reception (unable to handle many satellites, etc.)
  • jherdman 16y ago
    Many thanks! I learned something new today.