Field boundaries are generated by driving the GPS reciever equipped ATV around the field perimeter. Interior field structures such as waterways, ponds, and center pivot roads are mapped also. As shown waterway locations are precisely mapped and field acreages corrected. The soil sample collection points (blue dots) are on 2.5 or 5 acre grids. Jim drives to the sample point and collects a minimum of 5 cores. Samples are sent to Rock River Laboratory in Watertown, Wisconsin for analysis. In subsequent sampling years navigation to the same sampling point is easy. This means differences on lab results from year to year are real fertility differences rather than differences due to sampling location.