The present invention relates to a system and a method for real time detection of the position and behaviour of a plurality of animals which system comprises radio transmitter tags carried by the animals, where sensors receives signal from the tags, which system based of time delay of received signals at the sensors from the tags, perform calculation the position of the animals. It is the first object of the invention to achieve real time position of animal in a limited area. The object can be fulfilled by letting the system comprise a computer bases real time position calculation of the position of the animals, which system comprises a plurality of fixed reference radio transmitter tags, which system continuously based of received signal from the reference tags performs a calibration of the measured position of the animals. By using fixed reference radio transmitters together with tags that are performing equal radio transmission functions, it is possible by fixed placed sensors to receive first signals from the animal tags, but also signals from the fixed reference radio transmitter tags to perform an automatic calibration of all received signals from animals.
