iPod touch iPhone and iPod Touch AGPRS is it the same?

[GraceWu]

I use iPhone 3G AGPRS online 3G in google map. The blue colour circule will point my location. The pointer will move when i move. Is it commuicate with satellite?

I also try to use iPod touch google map for checking my location. The pointer also point my location. But i must need search with WiFi first. Even i did not login wifi. It can still check my location. Is it ipod touch commuciate with satellite, too?

I want to know they are the same skill for checking location? commuciate with satellite?

 

[goosnarrggh]

I use iPhone 3G AGPRS online 3G in google map. The blue colour circule will point my location. The pointer will move when i move. Is it commuicate with satellite?

I also try to use iPod touch google map for checking my location. The pointer also point my location. But i must need search with WiFi first. Even i did not login wifi. It can still check my location. Is it ipod touch commuciate with satellite, too?

I want to know they are the same skill for checking location? commuciate with satellite?

First a few definitions.
GPS = Global Positioning System
AGPS = Assisted Global Positioning System

GPRS = General Packet Radio Service, an almost totally unrelated technology.

The iPhone uses AGPS, where the phone itself actually receives information from satellites. It uses outside assistance via the celular network to help it make a first guess of which of the GPS satellites are within its line of sight at any point in time, so that it can fix in on them more quickly and expend less battery power.

The iPod Touch does not have any sort of GPS at all. Rather, it uses a database of the latitude/longitude and MAC addresses of a large set of known WiFi hotspots and fixed base stations. When it detects that is near one or more WiFi hotspots which are listed in its database, it can guess its approximate range from each to get an estimate of its position.

 

[sandman42]

The iPod Touch does not have any sort of GPS at all. Rather, it uses a database of the latitude/longitude and MAC addresses of a large set of known WiFi hotspots and fixed base stations. When it detects that is near one or more WiFi hotspots which are listed in its database, it can guess its approximate range from each to get an estimate of its position.

And, just like the way it updates the map data, the iPod Touch needs a wi-fi connection to access the database of hotspots. Without wi-fi access you can't go far (but it seems that you can go a short distance) before it stops working.