Accuracy Assessment of the eBee Using RTK and PPK Corrections Methods as a Function of Distance to a GNSS Base Station

<p>The use of unmanned aircraft systems to collect data for photogrammetry models has grown significantly in recent years. The accuracy of a photogrammetric model can depend on image georeferencing. The distance from a reference base station can affect the accuracy of the results. Positioning corrections data relies on precise timing measurements of satellite signals. The signals travel through the Earth's atmosphere, which introduces errors due to ionospheric and tropospheric delays. The aim of this research was to examine the eBee X and its global GNSS accuracy by comparing the RTK and PPK methods at different base station distances in photogrammetry models. Three factors were compared: 1) RTK and PPK methods, 2) local GNSS receiver via caster and NTRIP service corrections sources, and 3) base station distances between 2.4 km and 42.0 km. The eBee X flights occurred in 2023, at three different flying sites in Southwest Arizona in the United States. The <em>RMSE_XYZ</em> values from eight Check Points at each of three flying sites were measured with traditional GNSS survey methods. Through ANOVA testing, there were no statistical differences in <em>RMSE_XYZ</em> accuracy between RTK and PPK methods as well as between using a local Reach RS2 GNSS receiver via caster and NTRIP service for the eBee X; however, there was a statistical difference in <em>RMSE_XYZ</em> accuracy between base station distances of 2.4 km to 42.0 km, whereas, <em>F</em>(5, 33) = 11.99, <em>p </em>= 0.000. Specifically, base station distances of less than 16.2 km were significantly less than larger distances up to 42.0 km. These data suggest there was a significant difference in total accuracy based on the distance from the GNSS receiver base station providing corrections for the eBee X.</p>