GPS vs. TDOA (was Re: release date)

Jeff Andros jeff at bigredtj.com
Sun May 20 04:14:24 CEST 2007


>
>
> I think my question is why is everybody freaking out about the iPhone
> not having GPS? It will report location as close as 30 meters, usually
> within 100 meters and almost always within 300 meters. This accuracy
> is good enough for most applications. Even better cellular TDOA is
> accurate inside building as well as outside buildings (which in my
> experience GPS is not).  Are location detection services like
> TruePosition's U-TDOA (used by Cingular and T-Mobile in the USA) not
> available internationally?


Well, for one thing, it's my understanding TDOA is dependent on the cellular
provider giving you access to the data.  the AGPS on the NEO is capable of
running completely autonomously, or it can download the sat position data
from any data source.  In other words, typically you have to pay for access
to the TDOA data (whereas the US government provides GPS for "free"), and
you are always dependent on staying within the network.  There are quite a
few times I'm outside any coverage area (they start putting up towers in the
middle of the national forests, and I'm going to be pissed).  Also, the
early reports say the NEO's GPS is pretty good within buildings. Anyways, if
I'm wrong, let me know, but until then I'm glad we're going with GPS



-- 
Jeff
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