Field evaluation of four state-of-the-art astrogeodetic systems along the Mississippi River: CODIAC, VESTA, QDaedalus and TSACS Measurement

Deflections of the vertical, which quantify the direction of gravity near the Earth’s surface, are conventionally observed using astrogeodetic instruments. Our research compared four astrogeodetic systems together for the first time at similar observing sites: the zenith cameras COmpact DIgital Astrometric Camera (CODIAC) and VErtical by STArs (VESTA), and the robotic total station-based astrogeodetic systems QDaedalus and Total Station Astrogeodetic Control System (TSACS). We deployed the four systems at 32 sites on a 190 km profile along the Mississippi River between Baton Rouge and New Orleans, using 14 primary sites for direct comparison and subsequent performance evaluation with analysis of variance (ANOVA) and least-squares bias analysis. The results demonstrate that CODIAC is able to have an internal consistency better than ± 0.05 arcseconds for its 20-minute observations. Relative to CODIAC, the results suggest that, for 45-minute occupations in a typical astrogeodetic campaign, the VESTA, QDaedalus, and TSACS are capable of 0.15–0.20 arcsecond accuracy. One of the main goals of the survey was to fill gaps in geoid validation data in this region; these results will be used to test the National Geodetic Survey’s new GEOID2022 model and design future field campaigns. This survey also highlights the challenges of designing an astrogeodetic profile in a busy commercial corridor and serves as an instructive experience in 21st century operational geodetic astronomy.