A pump controller features a signal processor configured to respond to signaling containing information about three corresponding discrete arrays with respect to a discrete motor speed for each system position at a motor speed derived from 3D discrete distribution surfaces of motor power, pump differential pressure and flow rate by respective numerical interpolations; and determine corresponding signaling containing information to control a pump, or pumps in a system of pumps, or a system of pumps based upon a corresponding pump differential pressure and flow rate at the motor speed for a corresponding power reading value determined using a numerical interpolation of the three corresponding discrete arrays, the signaling received. The signal processor is configured to provide the corresponding signaling as control signaling to control the pump, or the pumps in the system of pumps, or the system of pumps.