The helicopter flies low over the trees on Watershed 1.  The watershed
boundaries had been programmed into a GPS (global positioning
system) unit in the helicopter, and each pass over the watershed was
recorded.  Once the pilot found his mark for the beginning of the next pass,
he stopped, hovered, turned on the spreader, and moved slowly forward
until the bucket was empty--about 10 to 15 seconds.  In this manner, he
"shingled" the application across the watershed in a north-south direction.