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Highlights

An evaluation of relative GNSS receiver accuracy was performed using a UAS-based GNSS accuracy testing system.

Abstract. Global navigation satellite system (GNSS) receivers commonly integrated into small unmanned aircraft systems (UAS) generally function in standard or differential fix configurations, providing horizontal and vertical accuracies of approximately ±5 meters and ±15 meters, respectively. The accuracy of GNSS positioning is an important factor with widespread implications, affecting domains such as precision agriculture, meteorology, and photogrammetry. In the context of atmospheric observations, spatial accuracy plays a critical role, particularly in applications related to barometric pressure and precipitable water vapor. Similarly, UAS-based photogrammetry applications rely on high geospatial precision for tasks including topographic mapping and environmental monitoring. As such, this study aimed to improve our understanding of GNSS positioning accuracy in UAS-based observations. The main objectives included (1) deploying a UAS-based GNSS accuracy testing system and (2) evaluating the static and dynamic short-term accuracy of L1 and L1/L2 GNSS receivers in RTK and non-RTK fix modes. Results indicated significant differences across receiver configurations and deployment strategies. RTK receivers displayed minimal mean error and consistent standard deviations, while non-RTK receivers exhibited greater mean error and variability, especially in elevation. Though the study did not conclusively confirm a consistent reduction in accuracy due to UAS deployment, findings suggest that RTK receivers substantially enhance accuracy by reducing position measurement error by two orders of magnitude (1–6 cm for RTK; 50–315 cm for non-RTK), thereby mitigating measurement variability attributable to timing or deployment strategy. In conclusion, this research contributed insights into GNSS accuracy for UAS-based observations and underscored the importance of considering receiver configurations and deployment strategies for position measurement during atmospheric and photogrammetric observations.