Prototype System for Unmanned Reference Point Determination at the Sub-Millimeter Level

The determination of reference points for telescopes is crucial for obtaining the local-tie vector for a multi-technology co-located station. Traditional methods suffer from labor-intensive fieldwork, long execution cycles, and systematic errors due to the incident angle of the total station's laser beam on the prism. In this paper, we propose an algorithm aligning the prism pointing vector with the prism-to-total station vector and introduce a pan-tilt platform and the Tianma VGOS telescope for sub-millimeter unmanned reference point monitoring. Our results show that the prototype system based on the pan-tilt achieves a formal error of +/- 100 mu m (1 sigma) in reference point positions with just 2.5 hr of automated monitoring. The consistency of reference point positions is comparable to the local control network accuracy. Single-direction observations may introduce a deviation of +/- 1 mm in the reference point compared to multiple direction observations. Preliminary experiments on the Tianma VGOS telescope have also shown that this system can efficiently automate the monitoring of prism scatter points (one measurement every minute) and achieve sub-millimeter horizontal precision in reference point positions within a single day. A unique algorithm that aligns the prism pointing vector with the prism-to-total station vector was derived An automatic sub-millimeter unmanned reference point monitoring prototype is designed and applied to the VGOS telescope Reference point coordinates solved by data sets from multiple directions are evaluated