Ever since reading David Pogue's review of iPhone 3G I've been puzzling over something he said in relation to the GPS receiver. Specifically, is it too small in the antenna department to be any good?
Here's what Pogue had to say about the iPhone 3G GPS antenna:
Unfortunately, there’s not much you can do with the G.P.S. According to Apple, the iPhone’s G.P.S. antenna is much too small to emulate the turn-by-turn navigation of a G.P.S. unit for a vehicle, for example.
Instead, all it can do at this point is track your position as you drive along, representing you as a blue dot sliding along the roads of the map. Even then, the metal of a car or the buildings of Manhattan are often enough to block the iPhone’s view of the sky, leaving it just as confused as you are.
At the time I found that to be a very curious statement given that I've handled countless GPS receivers and GPS-enabled devices that don't seem anywhere near the quality of the iPhone that can handle turn-by-turn navigation.
In an email Pogue told me that he'd been told by Bob Borchers, senior director of worldwide iPhone product marketing at Apple (he's also the guy that's featured in the iPhone tutorials), that the iPhone 3G's GPS chipset was weak and that the antenna was small. Pogue was also told that the tiny metal ring that you can see around the camera lens was part of the GPS antenna. When Pogue asked for confirmation that there would be no turn-by-turn software for the iPhone 3G he was told that the GPS was intended for quick "where am I" checks rather than navigation.
However, to complicate matters, Apple product head Greg Joswiak told ExtremeTech a different story:
What's the deal with GPS driving directions? Many developers have said that Apple's SDK license agreement prohibits the development of driving-directions apps, and the New York Times's David Pogue muddied the waters by saying that the iPhone's GPS isn't physically capable of providing driving directions. "According to Apple, the iPhone's G.P.S. antenna is much too small to emulate the turn-by-turn navigation of a G.P.S. unit for a vehicle," Pogue wrote.
That's wrong, Joswiak said; the iPhone's GPS is just like the GPS in other phones, many of which do provide driving directions. Rather, there are some murky "complicated issues" preventing driving directions apps at the moment. "It will evolve. I think our developers will amaze us," he said.
I'm speculating that those "complicated issues" revolve around liability in the event that the GPS receiver taking you for a nosedive into a bay somewhere.
OK, so what's the hardware that's behind the iPhone 3G GPS? A GPS has two critical components:
- The GPS chipset This is the bit that processes the GPS input (either from satellites of A-GPS data based on information received from cellphone towers) and translates that into a location.
- The GPS antenna The bit that picks up the GPS data from either the GPS satellite constellation or A-GPS data based on information received from cellphone towers.
Thanks to Kyle Wiens of iFixit.com, who kindly provided me with detailed photos, we can take a closer look at these two key components (if you'd like to see more close-up imagery of the iPhone 3G, check out this page on iFixit).
Here's the antenna (the cable with the "6" on it):
From the imagery that looks like a small patch antenna to me, but because it is soldered down the folks at iFixit don't want to risk breaking their iPhone 3G by removing it (I can't blame them).
Note: At present it is unclear to me whether that metal ring that surrounds the camera lens is anything at all to do with the GPS antenna. Personally I don't think that it is (if you look at this image on iFixit.com the only ribbon cable I can see going to that area is for the on/off switch), but I have asked Wiens to take a closer look for me on iFixit's dismantled iPhone 3G just to be sure though.
[UPDATE: Kyle Wiens has taken a look at this metal ring that surrounds the camera lens and it doesn't seem to be connected to anything - my guess is that it's decorative and nothing more.]
Here's the GPS chipset:
We know a lot more about the GPS chipset than we do about the antenna. The chipset is the Infineon PMB 2525, also known as the Hammerhead II. This single piece of silicon integrates both a high performance A-GPS baseband processor and a low-noise GPS RF front end. It also comes equipped with advanced multi-path mitigation software that eliminates large errors sometimes found in urban environments that are caused by reflected signal off buildings and other structures. This chip is no slouch.
So is the antenna small? Well, yes and no. If you compare it to say the GPS patch antenna of the TomTom 910 (it's the big square right slap bang in the middle of this image - via PocketGPS World) then yes it is. However, when compared to GPS antennas that you find in other cellphones or any other GPS-enabled consumer electronics product that isn't a dedicated GPS receiver, then no. The placement of the GPS antenna inside the iPhone 3G means that if you want best reception you need to hold the iPhone upright either in the portrait position or rotated 90° clockwise (of I guess flat on its front, but that would make looking at the screen a bit tricky).
The real deal maker/breaker for any in-car GPS receiver is whether it works inside a car. That said, even the best in-car system can have trouble working inside some vehicles, for example if they are fitted with metallized windshields. This is why most in-car GPS receivers come with the ability to attach an auxiliary external antenna. However, there's no connector for an external antenna on the iPhone 3G.
The bottom line ...
The bottom line is that there's no reason that the iPhone 3G can't be as good as any other cellphone-based GPS solution (in other words, turn-by-turn navigation is possible), but on the other hand it's unrealistic to expect it to to be as good as a dedicated in-car GPS solution.
[UPDATE: Steffen Breitbach dropped me an email to let me know that he has a blog dedicated to the GPS of the iPhone 3G called iGPS. I came across some interesting information here. First is this snippet relating to the iPhone SDK:
I had a look of what the iPhones SDK offers in terms of GPS. I found it a bit interesting, that you will get accuracy alongside positional info, but there is no flag that would report the origin of the data.
This means, that you won't be able to know if you just received an accurate GPS bearing or just a kind of cellular based triangulation "guess". Also, this implies that you can't choose if you want GPS data only upon initialization, although the chipset used would feature such functionality.
I also found a link to some more iPhone 3G teardown pictures.]
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