[morsch]

I think there's some value in communicating that the navigation system is confused by what you are doing. There are multiple reasons why it might be confused: I might have taken a wrong turn either on purpose or by accident. Or it might have an incorrect positional information or incorrect maps. The user is in a pretty good position to judge which is the case and to modify their trust into the navigation system appropriately, so it's useful when they are informed.

It doesn't have to be an obnoxious, repeated "Recalculating", I guess. A simple chime is pleasant -- but far less intuitive, you'd have to learn a new signal. Plenty of people are confused by navs making a chime sound when you're over the speed limit. An optical signal, like a big red X or a question mark on the display would be a good hint.