Study of time- and distance-dependent degradations of network RTK performance at high latitudes in Norway

In this study we examine the performance of a network real-time kinematic (NRTK) positioning service at high latitudes (≈70o\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\approx 70^o$$\end{document} N). The NRTK used is the Norwegian national positioning service “CPOS”. To test the performance, 6 geodetic quality receivers were deployed at various distances from the network receivers and used to collect positioning data for most of the year 2021. This test network is located in the night-time auroral oval region during normal conditions. Statistics are presented showing variation in performance as a function of the distance to the nearest NRTK receiver and as a function of the time-of-day. Performance is found to be significantly degraded during night-time, with approximately ten-fold increases of the occurrence of large positioning errors and significant increases in the time-to-fix. The distance from the network was also found to be a factor for significant performance degradation, with approximately ten-fold increases in the occurrence of large positioning errors when comparing results from a receiver close to the network (1.2 km) to a receiver a moderate distance away (11.5 km). The cause of the observed degradations are likely small-scale ionospheric density structures in the auroral oval region. Observational evidence of such gradients is shown.