Apparatus is provided featuring a signal processor or processing module configured at least to: receive signaling containing information about electrical responses to a transiting flow perturbation in at least three planes of a fluid flowing in a pipe, tank, cell or vessel sensed using a tomographic processing technique; and determine a flow rate of the fluid flowing in the pipe, tank, cell or vessel using a combined tomography and SONAR-based algorithm and signal processing technique, based at least partly on the signaling received.