Effects of Unmanned Aerial Spray System Flight Altitude and Collector Height on Spray Deposition Measured Using a Food Dye Tracer

The use of unmanned aerial spray systems (UASS) has increased owing to their many advantages. However, studies related to a standardized method to evaluate the spray performance of UASS are lacking. Therefore, in the present study, a quantitative analytical method using a food dye tracer was compared with the image analysis method, and the effects of experimental conditions on spray deposition were assessed. Concordance between the results of quantitative and image analyses was examined. The coverage of water-sensitive paper (WSP) and Medley Velvet (MV) was compared using image analysis. Moreover, the effects of flight altitude and collector height on spray deposition amount and effective spray width were evaluated. The results showed a significant correlation between the deposition and the coverage of MV (R2 = 0.6782, p-level < 0.001). The coverage of MV is different from that of WSP. In addition, the correlation coefficient between the coverage of WSP and that of MV was smaller than the correlation coefficient between depositions and the coverage of MV. Therefore, MV should be used instead of WSP for more accurate analysis. The lower the collector height, the smaller the deposition amount. The effective spray width increased as the distance between the collector and UASS increased, whereas the total deposition amount decreased when the collector was close to the ground. Overall, using a food dye tracer, both quantitative and qualitative analyses can be applied simultaneously, and this method may replace analysis using WSP.