Performance evaluation of a tracking total station as a position reference for dynamic GNSS accuracy testing

The dynamic accuracy of a tracking total station (TTS) was evaluated using a rotary test fixture to determine the viability of using a TTS as a position reference for dynamic global navigation satellite-based system (GNSS) accuracy testing. Tests were performed at angular velocities ranging from 0 to 3.72 rad/s at a radius of 0.635 m. A technique was developed to determine the average latency of the TTS measurement serial data output. TTS measurements were interpolated at a GNSS sampling interval to provide a method for direct comparison between TTS and GNSS position measurements. The estimated latency from the TTS serial data output was shown to be consistently near 0.25 s for all angular velocities and less variable when using a reflector-based machine target versus a prism-based target. Average positional error in the TTS position measurement increased with angular velocity from 3 to 90 mm, partly due to internal filtering which caused the magnitude of the TTS position measurement to decrease under stead-state sinusoidal motion. The standard deviation of error ranged from less than 1 to 20 mm as angular velocity increased. Sight distance from the TTS to the target was shown to have very little effect on accuracy between 4 and 30 m. The TTS was determined to be an adequate benchmark for most dynamic GNSS and vehicle auto-guidance testing but is limited by relatively large position measurement errors at high angular velocities.