Development and Validation of an External GPS Time Synchronization for Robotic Total Station Control

Abstract

Robotic total stations (RTS) offer great potential for use in the context of diverse kinematic measurement processes. However, a central challenge is the accurate and reliable combination of the polar measuring elements of the RTS with a higher-level global time reference. Global positioning system (GPS) time or coordinated universal time (UTC) are available for this purpose, but cannot be directly linked to the instrument. This paper presents a flexible concept for external synchronization of an RTS by means of an additional microcontroller. The developed synchronization box relies on extended communication commands of the instrument manufacturer's Measure & Stream application and is supposed to account for all significant offsets and latencies without additional laboratory calibrations. Using an independent validation procedure, absolute temporal offsets to a UTC-triggered laser tracker-based reference solution with superior accuracy are examined. This revealed a significant offset of 55 ms of the developed synchronization solution compared to the high accuracy reference, which is comparable to the determined latencies of related work in the context of laboratory calibrations. It is shown that further long-term investigations of the synchronization box are required and in particular the reliable and precise operability of the Measure & Stream application should be further investigated with a dedicated experimental setup.