Re: [mowbot] Ultrasonic position

Dave Everett (Deverett nospam at
Sun, 24 Nov 1996 14:18:32 +1100

robin nospam at wrote:
> power. The next point is that the transducers are somewhat directional.
> I haven't measured the beam, but I would guess it extends at least 90
> degrees in both axes from forward.

Common ultrasonic transducers have a half angle of about 15deg. so they
project a cone of 30deg. Signal can be receieved from outside 30deg, but
at greatly reduced repeatability.
> To reiterate: I would prefer a system which did not depend on
> pre-programmed knowledge. A much more satisfying (to me) and reliable
> system based on ultrasound would simply map landmarks and boundaries
> early in the proceedings and use these as points of reference to help
> compute future relative position fixes.
You'll get no argument from me there ;-)

Dave Everett                                Email: deverett nospam at
(c) 1996 - Copyright remains with the author unless explicitly stated