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?
Thanks for looking at this