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.
Precisely my point - much greater signal gain
that can be shared between a wider beam width, increased range, greater discrimination from ambient noise and possibly, reduced power,
Does anyone know of a project that uses this idea?
Not I, but it should be simply a matter of adapting present ultrasonic ranging approaches.