Abstract: A corner boom which includes a secondary water conduit is pivotally connected to the end of a center pivot boom which includes a primary water conduit and comprises a series of sections which pivot relative to one another about a center pivot point. The corner boom is supported by a wheeled tower which moves along a predefined path. A first encoder is positioned on the end of the center pivot boom to determine the angular separation between the corner boom and the end section of the center pivot boom. Other encoders are positioned, respectively, on a wheel of the support towers of both the end section and the next adjacent section of the center pivot boom to determine the angle between a reference line and a straight line connecting the center pivot point and the end of the center pivot boom.