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Old 07-21-2008, 07:37 PM   #1
Spiff
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does Assisted GPS (AGPS) REQUIRE a data package?

I've done some reading on wikipedia and googled and still haven't found a clear answer to this question....

With an iPhone 3G, which uses three forms of location finding (Assisted GPS, GPS and SkyHook's WiFi GeoMapping), I know for certain that SkyHook and regular GPS do NOT require any data from the cell networks.

GPS without assistance just requires a download from the GPS satellites of their configuration.

SkyHook's WiFi mapping requires an internet connection (via whatever you have enabled), but after that, it gets its location from SkyHook.

Now Assisted GPS involves downloading data from a cellphone tower which knows its exact location and has already determined what GPS satellites are in view.

So. If I have a WiFi connection, and have disabled my cellphone package, can I still use Assisted GPS? Is it a 'data package' download or is Assisted GPS like 911 cell phone service, available to all comers who are connected to the cell tower.

In short: I don't want to pay for a data package just to get Assisted GPS in an urban area (GPS works just fine in the non-urban canyons and non-treed areas where I live). I have no intention on using (since I pay for data downloads) the iPhone for mobile internet through Edge or 3G. So am I SOL to use AGPS w/o a data package or a cellphone account with the 3G monopoly in my area?
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Old 07-21-2008, 08:25 PM   #2
chabig
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A-GPS will work just fine without a cellular data plan, but how can you be sure that you'll have unrestricted access to wifi everywhere in your urban area? The phone has to have a data connection to use assisted GPS as well as to load the maps.

Your understanding of A-GPS is a bit wrong. Assisted GPS has nothing to do with knowing the location of cell towers. Assisted GPS simply takes advantage of an internet connection to enhance regular GPS. Instead of having to wait for certain GPS data to come over the relatively slow GPS signal, an internet connection can provide that data more quickly.

By the way, you forgot that another way the phone locates is by cell tower triangulation.

Last edited by chabig; 07-21-2008 at 08:28 PM.
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Old 07-21-2008, 08:28 PM   #3
Spiff
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re: wifi everywhere: already pay for it at a wifi-everywhere-place, annual fee, can use iPhone, iPod Touch, MacBook, whatnot on it.

yes re additional method not mentioned: cell tower triangulation

but my question still remains: is AGPS a data-package supplied to customers or is it available to all comers with or without smart-phones?
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Old 07-21-2008, 08:45 PM   #4
chabig
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It's not a data package. It's just network traffic that needs a data connection. Your phone needs to be able to contact the GPS assistance server for A-GPS, just like it needs to contact a time server to set the time. You also need a data connection for the maps.
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