Quote50km/h50K/(60*60) = 139 Meters/Sec.Doppler shift RF or laser is the only two things that I believe would be appropriate.Ray
50K/(60*60) = 139 Meters/Sec
Paul__B, this seems like it would be a viable way to do this, but I haven't seen any projects that actually use ping sensors between two Arduinos. They always use the reflection. It seems like you could get a lot greater distance by using the pings directly instead of reflections.
Does anyone know of a project that uses this idea?