An Attempt to Optimize Yield Maps by Comparing Yield Data from a Plot Combine and from a Combine Harvester

M. Bachmaier, M. Rothmund, H. Auernhammer


This paper deals with yield maps derived from yield monitor data of a combine harvester. Every
value of the yield map is determined by robust fitting of a paraboloid surface over a spatial
neighborhood around the point to be mapped, so that the influence of outliers is bounded or
canceled completely. The neighborhood used looks like the top view of the shape of the wings of
a butterfly gliding along the harvest tracks. To determine the optimal size and shape of the
neighborhood, an experiment was conducted with yield data measured by a plot combine (called
as true values) as well as yield monitor data from a commercial combine with a wider head,
which then harvested the same stretch behind the plot combine. The commercial combine was
equipped with two monitors. The yield maps are considered to have been optimized if the mean
squared deviations (mean squared error) between the true and mapped values has been
minimized. A large neighborhood proved necessary for both yield monitors, with the result that
the best yield maps obtained appear to be very smooth. Both yield maps could be optimized
further by rescaling the yield map values so that their dispersion increases.

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