A "true" base end station was one of a pair of stations at either end of a precisely measured (surveyed) baseline. Once simultaneous bearings from each base end station to a target were taken, since the distance between the stations (the baseline) was known, the range to the target from either station could be calculated through triangulation. If the target's bearing from each station was sent to a plotting room and input to a plotting board, the position of the target could be estimated and firing coordinates for a gun battery could be calculated.