A Bitmap Method for Determining Effective Combine Cut Width in Yield Mapping

In harvesting narrow row or broadcast crops such as wheat, the actual combine cut width can varysignificantly within a field. Assuming a constant combine cut width in the whole field to calculate crop yields will giveincorrect results. In this study, a bitmap method is developed to determine the effective combine cut width from GlobalPositioning System (GPS) positions of the combine in the field. The method consists of first initializing a bitmap thatrepresents the pre-harvest crop conditions in the field, and then progressively updating the bitmap to represent the up-todatecrop conditions during the harvest process. The effective combine cut width at each time step is derived bymanipulating the changes of the bitmap during that time period. An example application of the method is shown with yielddata for 1994 spring wheat. The average cut widths among combine passes varied from 1.18 m to 2.24 m, compared witha desired cut width of 1.52 m. The accuracy of the resulting yield maps was greatly improved by the bitmap method.