Monitoring goose-grazing activities and potential impact requires the use of a global positioning system (GPS). We conducted a test to compare the accuracy of the Magellan SporTrak Pro ®, an inexpensive hand-held GPS unit, to an expensive GPS with the capability of post-differential corrections (DGPS), the Trimble Pathfinder Pro ® XR. The hand-held unit can use the wide area augmentation system (WAAS) that was developed by the Federal Aviation Agency (FAA) and the U.S. Department of Transportation. WAAS is basically a system of satellites and ground stations that provide GPS signal corrections, giving us better position accuracy than the standard civilian signal..