inc of minnetonka minn the system disclosed in the 39 100 reissue patent includes a controller accessing a soil map indicating a soil characteristic for each portion of the field field locations and status maps indicating current crop input level at various locations in a field to be treated are monitored by a control system a crop input map is updated after a dispensing pass to provide a status record typical position locators for the machine in the field may include 34 dead reckoning 34 gps loran systems and the like u s pat no 5 355 815 discloses another closed loop variable rate applicator system the system operates by determining a soil prescription in near real time and dispenses crop inputs to the soil scene as a fraction of the soil prescription the 39 815 patent is also assigned to ag chem equipment company inc still another system is disclosed in u s pat no 5 453 924 issued sep 26 1995 to monson et al entitled mobile control system responsive to land area maps this system expands on earlier known applicator machine control systems by incorporating a network which links a host controller positioned within the operator cab to multiple controllers located at various points on the machine external to the operator cab it shall be understood that the control systems referenced herein describe systems which when properly configured with suitable algorithmic software can be easily adapted to monitor and control the speed and direction of the present inventive conveyor belt drive chain apparatus 100 with continued.