Patent ID: 7250901

Claim:
A positioning system, comprising: a passive, isotropic reflecting landmark at a fixed position; and a device configured to transmit an electromagnetic pulse, the pulse having a polarization; the device further configured to receive a return signal over a period of time, the return signal including a reflected pulse from the landmark, and to process the return signal so as to isolate the reflected pulse from the return signal and to determine a range from the device to the reflecting landmark; the reflecting landmark comprising: a first passive reflector for reflecting electromagnetic pulses; a second passive reflector for reflecting electromagnetic pulses; and a static structure configured to statically position the second passive reflector at an angle relative to the first passive reflector, wherein the angle is about 90°; the device including a data processor; at least one program module, executed by the data processor, the at least one program module containing instructions for: transmitting the pulse multiple times, each transmission of the pulse having a respective transmission beam pattern with a null over a different respective range of angles; determining from the return signals from the multiple pulse transmissions a first set of range candidates, each range candidate representing a possible range to the landmark, each range candidate having an associated range of angles; and analyzing the range of angles associated with each range candidate to produce a reduced set of range candidates that are consistent with one or more potential landmark positions.