Border detection

I plan to make a robot lawnmower that would be autonomous and know the borders of the garden and therefore cut the grass and then return to a base station on its own. However thinking how i could program it to know the borders of the garden , i can't think of an easy solution. RFID seems too expensive on a large expanse such as a garden, and sonar would be affected too much by shrubbery. I know on professional ones they use wire to mark borders but i don't know what sort of sensor is used, would magnets work?

Relative newbie :slight_smile:

Thanks for looking at this


How about a GPS?
The wire boundary is an inductive loop, the sort they use for deaf aids in buildings.
RFID will not have enough range.

i thought about GPS but i didn't think the accuracy would be high enough especially as if it was ten cm out it could fall into a trench, the question is if i could buy the inductive loop technology off the shelf.