Evaluation of NRTK-Based Heighting Techniques from Different Continuously Operating GNSS Reference Networks in Greece

Abstract

GNSS positioning using network-based real-time kinematic (NRTK) techniques, such as the virtual reference station (VRS) and the master auxiliary concept (MAC), is widely used in surveying and geomatics applications. The accuracy of the estimated height component by those techniques is known to be at the centimeter level although several factors, like the deployment of reference stations, the correction message transmission delay, the satellite signal availability and the employed software package, could limit the vertical accuracy obtained in practice. The scope of this paper is to present preliminary results from several field tests that were conducted by the Department of Geodesy and Surveying of the Aristotle University of Thessaloniki for the purpose of evaluating the heighting accuracy from different commercial providers of NRTK positioning services in Greece. Our aim is to investigate the actual positional quality of the vertical component from an end-user’s point of view by considering how different factors, such as the number of in-view satellites and their geometry, the duration of station occupancy, the distance to the reference stations and the choice of the applied correction method (VRS or MAC) might affect the final accuracy of the estimated heights. The validation of our results is based on high-quality height information that was independently obtained by precise spirit leveling over all considered test points.