A system configured to determine a location of a signal emitting device (204, 206, 214), the system comprising: at least one elevator car (103; 103a, 103b, 103c); a processor; and a memory comprising computer-executable instructions that, when executed by the processor, cause the processor to perform operations, the operations comprising: receiving first, second, and third data from at least one movable communication device attached to the at least one elevator car, each of the first, second, and third data comprising a unique identifier of the signal emitting device (204, 206, 214), a signal strength of a signal received by the at least one movable communication device from the signal emitting device (204, 206, 214), and a location of the at least one movable communication device when it received the signal, each of the first, second, and third data comprising different locations of the at least one movable communication device (204, 206, 214); and computing a location of the signal emitting device (204, 206, 214) based at least in part on the received first, second, and third data; characterised in that: the system further comprises a first movable communication device attached to the at least one elevator car and arranged to transmit the first data, and a second movable communication device attached to the at least one elevator car that is different than the first movable communication device, the second movable communication device being arranged to transmit the second data. at least one elevator car (103; 103a, 103b, 103c); a processor; and a memory comprising computer-executable instructions that, when executed by the processor, cause the processor to perform operations, the operations comprising: receiving first, second, and third data from at least one movable communication device attached to the at least one elevator car, each of the first, second, and third data comprising a unique identifier of the signal emitting device (204, 206, 214), a signal strength of a signal received by the at least one movable communication device from the signal emitting device (204, 206, 214), and a location of the at least one movable communication device when it received the signal, each of the first, second, and third data comprising different locations of the at least one movable communication device (204, 206, 214); and computing a location of the signal emitting device (204, 206, 214) based at least in part on the received first, second, and third data; receiving first, second, and third data from at least one movable communication device attached to the at least one elevator car, each of the first, second, and third data comprising a unique identifier of the signal emitting device (204, 206, 214), a signal strength of a signal received by the at least one movable communication device from the signal emitting device (204, 206, 214), and a location of the at least one movable communication device when it received the signal, each of the first, second, and third data comprising different locations of the at least one movable communication device (204, 206, 214); and computing a location of the signal emitting device (204, 206, 214) based at least in part on the received first, second, and third data;