Patent ID: 7656291

Claim:
A boundary proximity determining system for wirelessly defining a boundary having a programmable shape and for indicating a current location of a rover unit with respect to the boundary, said boundary proximity determining system comprising: a base station unit, said base station unit generates at least one pair of magnetic fields, each magnetic field being separately identifiable and having a principal axis, the principal axes being mutually directionally diverse and lying substantially within a common two-dimensional plane of operation; and said rover unit being mobile and including an auxiliary communications module, said rover unit measures magnetic field properties of each respective magnetic field at the current location of said rover unit, the magnetic field properties measured at the current location of said rover unit indicating the current location of said rover unit with respect to said base station unit, said rover unit operates in a first mode of operation and a second mode of operation, when said rover unit operates in the first mode of operation, said rover unit defines the boundary by measuring the magnetic field properties of each respective magnetic field at a multiplicity of sample locations along the boundary and by storing the magnetic field properties measured at the sample locations, the magnetic field properties measured at each sample location indicating the location of the respective sample location with respect to said base station unit, when said rover unit operates in the second mode of operation, said rover unit determines the current location of said rover unit with respect to the boundary by comparing the magnetic field properties measured at the current location of said rover unit to the magnetic field properties measured at the sample locations, the auxiliary communications module transmitting an indicator signal indicating the location of said rover unit with respect to the boundary.