A method for determining a position of a rotatable arm of a center pivot irrigation system may comprise providing a pivot arm position sensing system including a tower unit positionable at the rotatable arm and a GPS receiver at the tower unit, and receiving, from a user over a communication network, a schedule for operating the irrigation system as the rotatable arm rotates. The schedule may include at least two instructions for taking an action by the irrigation system with each instruction including an action and a corresponding location for the action. The method may further include downloading the schedule over a communication network to storage on the position sensing system, determining a location of the tower unit as the tower unit moves about the center of rotation using the GPS receiver, and initiating an action when the location corresponds to the location in one of the instructions.
