At 07:14 AM 11/18/97 +0100, you wrote:
>Michael S. Hagberg wrote:
>>
>> no not funny,
>>
>> i don't think that any of us (with lawns) haven't thought of this
project. i
>> see they have a link to the 2x compass. i read the specs and didn't feel
>> that this device was accurate enough for a guidance system. counting ticks
>> on the wheel revolutions won't work either because the ground is not
flat. i
>> saw a robot show on tv where they used dual gps receivers about the size of
>> a pack of cigeretts. does anyone know who makes devices like this. or how
>> would you send a robot 200 feet (70 meters) down a property line without
>> mowing over your neighbors flower garden?
>>
>> michael
>
>the gps is not too reliable at this resolution :)
>the vector is good, but you have to measure the distance from a few
>points to make a reliable navigation system
>(or you could detect the position of the 'mower with some kind of ccd
>and send the directions back thru radio)
>

How about a metal wire buried a few inches below ground at the edges of
your property?  You could have the wire conduct an oscillating current
(maybe 60Hz).  The landmower would then detect the resulting EM field using
a simple high gain amplifier, which would tell the landmower that it is at
the edge of the property.  Or perhaps even better, bury the wire in the
path of the lawnmover so that the mower simply follows the buried wire
around the yard, avoiding trees, etc.

Dave Hackos
Dept. of Physiology
University of California, San Francisco