Abstract: A method and system are provided for teaching a robotic accessor the actual location of the center of targets in an automated storage and retrieval system, the actual locations being different from expected or nominal locations due to tolerances in parts and assembly. A bar code scanner, which can also be used to read the identity of items stored in the system, is used to locate and scan each target and transmit to a controller a message containing the time during each sweep of the scanning beam when one side of the target is first detected and the time during each sweep when a second, opposing side is detected. The processor calculates the physical center of the target based upon the transmitted times from one or more sweeps. The coordinates of the center are then stored and later used to accurately locate and retrieve an item stored in the system. An optional calibration technique compensates for any angular offset in the bar code scanner.