GO My way 2009 depends on the built-in Location Services of the iPhone operating system. You can navigate with iGO My way 2009 as soon as the iPhone receives the GPS signals, calculates the position and makes it available for the applications.
Please note however, that there are applications that do not require accurate, GPS-based location information. These applications may operate with the far less accurate GSM network-based location information. Unfortunately this location method is not accurate enough for turn-by-turn navigation.
Furthermore, even the GPS-based location may be (or may become) inaccurate under some conditions. iGO My way 2009 requires a relatively high level of accuracy in order to be able to provide accurate guidance. Other applications may set a lower threshold.
When your iPhone loses the GPS signals, or when the location becomes inaccurate (due to whatever reason), iGO My way 2009 doesn't immediately announce that the position is lost. Instead, it applies sophisticated algorithms (considering e.g. road geometry*) in trying to predict the most likely position and to continue guidance. However, as the level of uncertainty gets beyond a threshold, it would be too risky to pretend to know the location. Setting this threshold was the result of carefully balancing perceived service quality versus the risk of wrong guidance.
Tip: Watch for the little brown dot around the vehimarker - that represents the last location data as received from the iPhone OS, and iGO My way 2009 displays that without any delay or filtering. Sometimes that dot lags significantly behind the vehimarker.
* Tunnels are special cases: in tunnels, iGO My way can safely assume that you are moving along the road and can continue location display and guidance based on the speed at which you entered the tunnel.
