Correct me if I am wrong; iPhone 3GS and 3G only comes with Assisted GPS which means it utilises GPRS, Edge or 3G connection to detect the signals from the transmission towers and lock your position based on the signals they received from the tower. It does not directly utilises the satellites. It only gives an estimation on your position based on the positions of the towers. Thus, it is faster to lock and are able to use it indoor. Conclusion, fast locking, can use indoor but not accurate.

Unlike the Standalone GPS, it fully utilises the positions of the satellites directly to lock your position. Thus it will take a longer time to locked. It also not able to function indoor. Conclusion, slow locking, cannot use indoor but accurate.

Some models like HTC Touch Pro uses both. Thus, when the Standalone GPS cannot lock your position, it will utilise the A-GPS

---

Added on December 18, 2009, 10:40 pmI am also looking at an external Standalone GPS device particularly bluetooth ones because iPhone only comes with A-GPS. Where did you get yours? Is it a Standalone GPS or A-GPS?

---

Added on December 18, 2009, 10:46 pmI never tried any of these; but I have tried Garmin in Sabah and found that its good. I have also tried the Google Maps and found that Garmin is still better as the map is more complete and no need GPRS, Edge or 3G connections to open the map.

However, iphone is using only A-GPS and this will make all these maps not so accurate especially in Sabah where the telecommunication towers are weaker.

---

Added on December 18, 2009, 10:50 pmContacted Garmin and according to them, they currently have no plan to develop the iPhone version.

This post has been edited by DavidL: Dec 18 2009, 11:26 PM