According to the present invention, a method is provided for sensing a fluid flow within a pipe having a lengthwise axis to determine a parameter of the fluid flow. The method includes the following steps: a) providing an array of more than two ultrasonic sensors, each sensor having a transmitter and a receiver; b) disposing the transmitter and receiver of each sensor orthogonally relative to the lengthwise axis of the pipe; c) receiving ultrasonic signals using the receivers, which received signals result from initial signals transmitted from the transmitters of the ultrasonic sensors; d) processing the received signals from each sensor by projecting the received signals against a sine function and a cosine function, high pass filtering the projected signals, and using the high pass filtered projections to create an arrival vector within a complex plane, wherein the high pass filtered arrival vector is a rectified frequency doubled signal; and e) determining the parameter of the fluid flow using the arrival vector.