The idea of virtual fences is kind of scary in a Philip K Dickensian way. Perhaps because it’s not such a great leap to envision people being shepherded from place to place, all remotely controlled by implacable black necklaces. Whatever.
‘Butler and his colleagues have written software that transmits the chosen GPS co-ordinates of a virtual fence to head-collars worn by the cows in the field. When a cow strays towards these co-ordinates, software running on the collar triggers a stimulus chosen to scare the cow away, such as a sound or a small electric shock – this is the “virtual” fence. The software also “herds” the cows when the position of the virtual fence is moved.’