[alexhawdon]

As others have pointed out, it's the noisiness of the compass sensor itself that's the real problem - this isn't something that can be fixed in UI.

Assuming you're pointing the device in the direction of travel, you can move forwards and combine the new position information to reduce this noise - I believe Google Maps does this on Android.

One could possibly envisage also using data from the phone's camera and corresponding it to street view images which (presumably) all have a known direction. There would be issues with the amount of data being sent up to Google to do this and the experience would be a bit wacky as you'd have to point your phone up (or at least horizontally, assuming you weren't surrounded by pedestrians etc) and maybe scan it around a bit...

You've got me thinking about Google Maps in general though. A feature I'd love to see is a map layer for mobile network coverage. I'm taking a trip this weekend somewhere quite rural and would like to try out the turn-by-turn directions, and it would be good to know ahead of time if some cruicial point in the route simply isn't covered by a signal - you never know until it's too late! They could perhaps combine this with the routing algorithm to offer you an alternate route where you don't have to make a turn in a no-reception area. When caching is implemented further down the line this could be used to provide a sensible 'minimal caching' option that just stores the bits you won't be able to receive on the road.

[easytiger]

I've driven thousands of miles via android TbT navigation and surely for many of those i was out of signal. But because of the way it gets a complete direction list at the beginning it seems to never run out of things to say. I think this is an issue that's already been solved for most people's use cases.

[ars]

Why not just use the inertial sensor to always keep track of which way the phone is pointing?

I know those drift after a while, but with GPS corrections, it should certainly manage to keep orientation while someone is getting off a bus, or turning around in a parking lot.