Effect of DSM Spatial Resolution from UAV Photogrammetry on Rooftop Photovoltaic Potential Assessment

This study quantitatively evaluates the effect of the spatial resolution of a digital surface model (DSM) derived from unmanned aerial vehicle (UAV) photogrammetric data on rooftop photovoltaic potential assessment. A baseline DSM with a spatial resolution of 1.26 cm was used to generate six DSM variants with cell sizes of 2.5, 5, 10, 25, 50, and 100 cm. For each variant, roof slope and aspect were derived, annual solar irradiation was modelled, and the inclined roof area suitable for photovoltaic (PV) installation (APV), potential PV capacity (PPV), and predicted annual electricity generation (EPV) were determined. The analysis was conducted for 29 buildings by comparing the results obtained from each DSM variant with those derived from the baseline DSM. For the baseline variant, APV was 995.17 m2, PPV was 199.03 kWp, and EPV was 135,900.09 kWh/year. The smallest differences were observed for the 2.5 and 5 cm DSM variants, while the 10 cm variant also showed relatively close agreement with the baseline. For DSM variants with cell sizes of 25 cm or larger, building-level differences generally became more pronounced. Roof aspect showed particularly high sensitivity to DSM spatial resolution, with the mean absolute error (MAE) of whole-building circular mean aspect relative to the baseline DSM increasing from 6.43° for the 2.5 cm variant to 56.56° for the 100 cm variant. The median absolute relative difference increased from 0.83% to 22.86% for APV and from 0.91% to 26.81% for EPV. For the 100 cm variant, the aggregated values of APV and EPV were lower than the baseline values by 6.35% and 4.48%, respectively. The results indicate that DSM spatial resolution affects all analysed stages of rooftop photovoltaic potential assessment, while aggregated values may not fully reflect the differences observed between individual buildings. Under the baseline atmospheric assumptions, the 10 cm DSM was the largest tested cell size satisfying the adopted screening criterion, with median absolute relative differences of 5.24% for APV and 4.86% for EPV. However, the atmospheric sensitivity analysis showed that the largest qualifying cell size varied from 2.5 to 25 cm, indicating that DSM resolution selection depends on the adopted modelling assumptions.