The nature of operation for Wireless Sensor Networks requires tracking and locating the sensed phenomena in the environment where the nodes are deployed in. However, network life time is an important issue that requires all the possible efforts to control and maintain a fair and long life time. Mobility adds a more complex issue in tracking the sensed phenomena. This paper presents a new approach in locating mobile sensor nodes by utilizing the method of Trilateration to load the start-up location of the node and a digital compass to update the node's location according to its movement speed. Simulation results show an improvement in terms of energy consumption against pure Trilateration method without jeopardizing the location accuracy. © 2012 IEEE.