Spatial methodology for unmanned aerial spraying systems performance evaluation in vineyards

Unmanned Aerial Spraying Systems (UASS) are increasingly used for plant protection in vineyards, but their adoption is limited by the lack of repeatable field procedures for evaluating spray deposition in relation to canopy structure and flight settings. This study proposes and tests a spatial methodology for assessing UASS spray performance by integrating UAS-derived canopy characterization with water-sensitive paper (WSP) deposition measurements. The approach combines preliminary spray-width characterization, canopy-volume mapping, spatially representative WSP placement, and post-flight analysis of deposition patterns within homogeneous canopy zones. Field data were used to evaluate how canopy architecture related to spray coverage, droplet distribution, and canopy penetration across vineyard sampling positions. Results showed that canopy structure was associated with deposition patterns: denser canopy zones tended to show reduced deposition in lower sampling layers, whereas open canopy conditions produced higher but more variable WSP responses. The findings indicate that average deposition values alone are insufficient to describe UASS performance, because they may conceal local under-treated areas, excessive overlap, and penetration limits. The methodology also highlighted the importance of defining an effective operational swath and overlap before field application and of aligning WSP sampling with canopy variability rather than relying only on regular grids. Although WSP observations remain punctual and require adequate sampling density for robust spatial interpretation, the proposed workflow provides a practical framework for spatially explicit UASS performance assessment in vineyards. This approach can support improved experimental protocols, optimization of flight parameters, and future development of user-oriented tools for sustainable UASS-based spray applications in tree-crop systems.