The Field Grid Sense system was adapted to locate and record crop yield in the field. Accurate measurement of yield in spatially variable fields is needed to achieve maximum profitability in crop production. The harvester system is composed of a laptop computer, data acquisition system, fifth wheel, and an ultrasonic level sensor assembled on a combine. The fifth wheel, in combination with travel lanes, is used to identify yield with position where yield is determined by the change of grain volume in the combine hopper. Yield maps can be generated from the collected data and then used as a production management tool in conjunction with other field characteristic information.