The precision and accuracy of a Leica MultiStation 60-based QDaedalus astrogeodetic measurement system are determined through observations at two locations in Switzerland. The precision of the QDaedalus was determined as 0.1″ for the N-S and E-W deflections of the verticals (DoVs) through 118 series of observations collected over 13 nights (in a 44-day observation period) at the HEIG-VD test station. The accuracy of the QDaedalus system was established by simultaneous parallel observations over two nights using the CODIAC system at the Zimmerwald Observatory. The differences between them were found to be 0.09″ and 0.02″ for the N-S and E-W DoV components, respectively. From these results, the accuracies of both DoV components can be interpreted as 0.1″. We also found a large systematic trend in the observed N-S DoV data at the HEIG-VD test station (0.008″/day). This study is the most extensive thus far for determining the precision and accuracy of the QDaedalus system for astrogeodetic measurements; it is also the first time that QDaedalus system’s accuracy has been established using parallel observations.

The Digital Zenith Camera Systems (DZCSs) are dedicated astrogeodetic instruments used to obtain highly accurate astrogeodetic vertical deflection (VD) data. The first Turkish DZCS, the Astrogeodetic Camera System (ACSYS), was developed in Istanbul, Turkey in 2015. The ACSYS was capable of determining astrogeodetic VDs with an accuracy of ~0.3 arcseconds. However, it had some limitations in observation duration: because of the semi-automated mechanical design, levelling the system towards zenith was a time-consuming process. Since 2016, the ACSYS has been modernized through system upgrades and new technological components. In this paper, we describe the instrument design of the new DZCS-ACSYS2-observation procedures, evaluation of the test data and calculations of these data. The preliminary ACSYS2 astrogeodetic test observations were conducted at Istanbul Technical University (ITU) test station. The standard deviation results of the repeated observations reveal a VD measurement precision of ~0.3 arcseconds for both the North-South and East-West components. To investigate the accuracy of the system, a lightweight total station based-geodetic system-QDaedalus-was also used at the ITU test station. The comparison of the VDs data between ACSYS2 and QDaedalus system shows that the ACSYS2 can produce reliable VDs data.

Nowadays, zenith telescope-based digital zenith cameras (DZC), such as the COmpact DIgital Astrometric Camera (CODIAC) and VErtical by STArs (VESTA), are used to determine highly precise astrogeodetic deflections of the vertical (DoVs). The CODIAC and VESTA were developed by Eidgenossische Technische Hochschule (ETH) Zurich and University of Latvia, respectively, and only two CODIACs and four VESTAs were produced. The CODIAC has an established accuracy higher than 0.05″, while the accuracy of VESTA is ~0.1″. These two DZCs, which are the most used DZCs of the last decade, were used effectively over many survey campaigns. In this study, we used both the CODIAC and VESTA to conduct simultaneous observations at the School of Management and Engineering Vaud (HEIG-VD) in Yverdon-les-Bains, Switzerland, over five nights in August 2021. Our DZC measurements with CODIAC and VESTA mark the second time that simultaneous parallel observations were made with two different DZCs. Additionally, the VESTA was never tested against another DZC through comparative simultaneous measurements. These comparative measurements between the VESTA and CODIAC allowed for VESTA precision validation and checking the agreement between the two DZCs. The results of repeated, comparative DoV observations over five nights at HEIG-VD revealed a DoV measurement precision of VESTA around 0.13–0.16″ for 15 min long observation session and 0.10–0.13″ for 50 min long observation session. Mean DoV differences between CODIAC and VESTA at HEIG-VD were 0.08″ and −0.06″ for the North–South and East–West components, respectively.

Astrogeodetic deflections of the vertical (DoVs) are close indicators of the slope of the geoid. Thus, DoVs observed along horizontal profiles may be integrated to create geoid undulation profiles. In this study, we collected DoV data in the Eastern Swiss Alps using a Swiss Digital Zenith Camera, the COmpact DIgital Astrometric Camera (CODIAC), and two total station-based QDaedalus systems. In the mountainous terrain of the Eastern Swiss Alps, the geoid profile was established at 15 benchmarks over a two-week period in June 2021. The elevation along the profile ranges from 1185 to 1800 m, with benchmark spacing ranging from 0.55 km to 2.10 km. The DoV, gravity, GNSS, and levelling measurements were conducted on these 15 benchmarks. The collected gravity data were primarily used for corrections of the DoV-based geoid profiles, accounting for variations in station height and the geoid-quasigeoid separation. The GNSS/levelling and DoV data were both used to compute geoid heights. These geoid heights are compared with the Swiss Geoid Model 2004 (CHGeo2004) and two global gravity field models (EGM2008 and XGM2019e). Our study demonstrates that absolute geoid heights derived from GNSS/leveling data achieve centimeter-level accuracy, underscoring the precision of this method. Comparisons with CHGeo2004 predictions reveal a strong correlation, closely aligning with both GNSS/leveling and DoV-derived results. Additionally, the differential geoid height analysis highlights localized variations in the geoid surface, further validating the robustness of CHGeo2004 in capturing fine-scale geoid heights. These findings confirm the reliability of both absolute and differential geoid height calculations for precise geoid modeling in complex mountainous terrains.