A system for identifying an item within a sensing volume, wherein the system comprises: a conveyor belt configured to carry objects and to move the objects relative to the sensing volume; a plurality of object sensors, each object sensor configured and arranged to determine at least one parameter describing the objects as they are relatively moved by the conveyor belt with respect to the sensing volume, each object sensor having a known position and attitude with respect to the sensing volume; a position sensor, configured and arranged to measure the position of the conveyor belt and to produce position information which indicates the position of the conveyor belt relative to a fixed reference location in the sensing volume; and a processor, configured and arranged to receive the parameters from the object sensors and to associate the parameters with respective ones of the objects on the basis of the position information and on the basis of the known position and attitude of the object sensor that determined each respective parameter, wherein the system is an asynchronous system which does not incorporate a system clock, each object sensor is configured to output the at least one parameter as soon as the at least one parameter is determined and the position sensor is configured to output position information as soon as the position information is produced, wherein the position information does not comprise system clock information, and wherein: the processor is configured and arranged to associate the parameters with respective ones of the objects without taking into account system clock information to compare, for each object having at least one associated parameter, the at least one associated parameter to known item parameters to assign an item identification to the object. a conveyor belt configured to carry objects and to move the objects relative to the sensing volume; a plurality of object sensors, each object sensor configured and arranged to determine at least one parameter describing the objects as they are relatively moved by the conveyor belt with respect to the sensing volume, each object sensor having a known position and attitude with respect to the sensing volume; a position sensor, configured and arranged to measure the position of the conveyor belt and to produce position information which indicates the position of the conveyor belt relative to a fixed reference location in the sensing volume; and a processor, configured and arranged to receive the parameters from the object sensors and to associate the parameters with respective ones of the objects on the basis of the position information and on the basis of the known position and attitude of the object sensor that determined each respective parameter, wherein the system is an asynchronous system which does not incorporate a system clock, each object sensor is configured to output the at least one parameter as soon as the at least one parameter is determined and the position sensor is configured to output position information as soon as the position information is produced, wherein the position information does not comprise system clock information, and wherein: the processor is configured and arranged to associate the parameters with respective ones of the objects without taking into account system clock information to compare, for each object having at least one associated parameter, the at least one associated parameter to known item parameters to assign an item identification to the object.