Understanding new agricultural spraying tools aims to reduce cost, promote operational gains, and achieve profitability. This work evaluates the precision and accuracy of two drones (named X and D so as not to single out manufacturers) with respect to volume applied at field scale. Both drones utilized identical droplet dispersion systems (rotary discs). The experiment involved mapping identical fields using both manual (field control points) and digital (high-resolution 4K aerial imaging) methods across incremental area sizes of 60, 72, 252, 576, and 1008 m². Applications were carried out with the same flight parameters and repeated five times. A precise scale was used to weigh the drones before and after application, allowing for comparison between planned and actual application volumes (l/m²).
Accuracy was assessed using the normalized root mean squared error, while precision was evaluated through the coefficient of variation across repeated measures. Digital mapping on X for the areas with 60 and 72 m² was not possible due to software limitations. Our findings revealed no consistent advantages in accuracy or precision between digital and manual mapping for areas up to 576 m². However, for the largest area tested (1008 m²), digital mapping demonstrated superior accuracy (+2% for X and +10% for D) and precision (+4% for X and +12% for D) compared to manual mapping.
Overall, drone D exhibited a lower average volume sprayed (-6.1 ± 25.8 l/m2) than anticipated, raising concerns about its effectiveness in pest management due to potential inadequate coverage. In contrast, drone X exceeded the expected volume (11.4 ± 19.1 l/m²). This discrepancy suggests that drone D may require recalibration or optimization to ensure it meets the desired spraying volumes. The accuracy and precision of volume sprayed varied with area, with higher sizes having higher accuracy and precision.
Further studies are recommended to evaluate prescription systems for localized application with drones. This evaluation highlights the differences in spray accuracy and precision for different OEMs and shows the importance of verifying the calibration, precision, accuracy and limits of robotic spraying technology, as well as the possibility of incorporating these limits on the product label to increase farmer success. Additionally, significant variations between digital and manual mapping methods highlight the need for careful consideration when selecting mapping techniques.

Ana Flávia Rufino Tamara

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