A system is described for determining a relative location of a plurality of items upon a plurality of platforms. The system may include a memory, an interface, and a processor. The memory may store a first item, a second item, a first period of time and a second period of time. The interface may be operative to communicate with a user and an antenna. The antenna may be able to detect an item for a period of time. The processor may be operative to receive from the antenna, via the interface, the first item, the first period of time, the second item and the second period of time. The processor may determine whether the periods of time overlap. If the periods of time overlap the processor may communicate to the user that the items are upon the same platform, otherwise that the items are on consecutive platforms.