Patent ID: 6839972

Claim:
A position determination system, comprising: a first measuring apparatus, including a first sensing device having a sensing field for obtaining positional data of a first testing target relative to the first sensing device; a calibration target rigidly linked to the first sensing device, wherein the positional relationship between the first sensing device and the calibration target is known; and means for repositioning the sensing field of the first sensing device without altering the positional relationship between the first sensing device and the calibration target; and a second measuring apparatus, including a second sensing device having a sensing field for obtaining positional data of a second testing target relative to the second sensing device; a calibration sensing device rigidly linked to the second sensing device for obtaining positional data of the calibration target relative to the calibration sensing device, wherein the positional relationship between the second sensing device and the calibration sensing device is known; means for repositioning the sensing field of the second sensing device without altering the positional relationship between the second sensing device and the calibration sensing device; and a data processing system configured to couple to the first and second sensing devices to carry out the machine-implemented steps of: determining whether the first testing target is within a specific sensing field of the first sensing device by comparing data sensed by the first sensing device with prestored data representing the first testing target being within the specific sensing field of the first sensing device; and determining whether the second testing target is within a specific sensing field of the second sensing device by comparing data sensed by the second sensing device with prestored data representing the second testing target being within the specific sensing field of the second sensing device.