In reply to:

As well as: seeing an intersection approach in Roadmap, I get the feeling that I've overshot it sooner than I would have if it were just in GPSapp. Any comment on this?



Yeah, I've noticed this too. I'm not really sure if the problem is that Roadmap is a little slow (you should see all the stuff Roadmap does in the code!), or the fact the NMEA messages and updates only come once per second and the delay is more noticeable when you can actually see the intersection on the screen. I was thinking about putting in a GPS with a binary mode that updates more than once a second to test this, but I'm not sure GpsD or GPSApp support faster updates.