eLawnmower positioning/tracking - Ultrasound beacons?

Hi

I see positioning comes up a lot, but I haven't found anything that seems to fit my application.

I want to automate my lawncare - mowing, racking and weeding.

I am starting with the mower - but all will have similar 'issues' around covering the whole area of lawn.

The lawn is an irregular shape and has obstacles (trees).

The basic mower control/pattern will be up, turn, down (or up, and reverse back down... maybe) but the real question is keeping the mower straight (with arcs for the obstacles) and not missing bits.

I think the choice is really between absolute positioning, or following a path... my currently though is to use ultrasound range finders doing x/y plotting - but as there won't be anything to bounce it off, have a couple of 'beacons' or 'repeaters' strategically placed, So the arduino kicks off some pings fairly non-directionally, and the beacons just listen out and echo them back... and I just have to recalibrate the distance to allow for the extra time it takes for the 'beacon' to hear and reply... and triangulate an absolute position...

Or is GPS better? :slight_smile: