A system for positioning animal tags, the system comprising a central control unit, a set of at least three anchor base stations (BSA1, BSA2, BSA3, BSA4) whose respective positions are known, and a clock-signal source configured to provide a global time reference to the central control unit and the anchor base stations (BSA1, BSA2, BSA3, BSA4), the system being adapted to determine a location of an intermediate base station (BSI1, BSI2, BSI3, BSI4, BSI5) added to the system, the anchor base stations (BSA1, BSA2, BSA3, BSA4) are arranged in a frame around an area in which positions for animal tags are to be determined based on propagation-delay measurements of signals emitted by the animal tags using the global time reference, the anchor base stations being located in a common plane, characterized in that the central control unit is configured to: receive a notification that the intermediate base station has been arranged between first and second anchor base stations (BSA1, BSA3) of said anchor base stations, such that in a projection onto the common plane, the intermediate base station is located on a straight line between the first and second anchor base stations (BSA1, BSA3), and in response to the notification determine, based on propagation-delay measurements of a signal emitted by the intermediate base station and by using the global time reference, a first calculated distance (d BSA1-BSI5) between the first anchor base station and the intermediate base station, and a second calculated distance (d BSA3-BSI5) between the second anchor base station and the intermediate base station; obtain an elevation indicator specifying whether the intermediate base station is located in the common plane, above the common plane, or below the common plane, and determine the location of the intermediate base station based on the first and second calculated distances (d BSA1-BSI5; d BSA3-BSI5) and the elevation indicator, determine the location of the intermediate base station by calculating a deviation distance (Δe BSI5) from the common plane using the first and second calculated distances (d BSA1-BSI5; d BSA3-BSI5), a known reference distance (d BSA1-BDA3) between the first and second anchor base stations (BSA1, BSA3), the elevation indicator and by applying the Pythagorean theorem. receive a notification that the intermediate base station has been arranged between first and second anchor base stations (BSA1, BSA3) of said anchor base stations, such that in a projection onto the common plane, the intermediate base station is located on a straight line between the first and second anchor base stations (BSA1, BSA3), and in response to the notification determine, based on propagation-delay measurements of a signal emitted by the intermediate base station and by using the global time reference, a first calculated distance (d BSA1-BSI5) between the first anchor base station and the intermediate base station, and a second calculated distance (d BSA3-BSI5) between the second anchor base station and the intermediate base station; obtain an elevation indicator specifying whether the intermediate base station is located in the common plane, above the common plane, or below the common plane, and determine the location of the intermediate base station based on the first and second calculated distances (d BSA1-BSI5; d BSA3-BSI5) and the elevation indicator, determine the location of the intermediate base station by calculating a deviation distance (Δe BSI5) from the common plane using the first and second calculated distances (d BSA1-BSI5; d BSA3-BSI5), a known reference distance (d BSA1-BDA3) between the first and second anchor base stations (BSA1, BSA3), the elevation indicator and by applying the Pythagorean theorem.