Long-term monitoring using GNSS: Lessons learned and experiences from 20 years of operation

Global Navigation Satellite Systems (GNSS) like GPS, Galileo, GLONASS and Beidou are used for monitoring of civil structures and natural phenomena since the 1980s. However, most of the implementations were either short term or realized in a very controlled environment. In this article we report about the experiences of more than 20 years of GNSS based monitoring of a large-scale object. In 1999 the GNSS monitoring system was developed and installed at a deep-seated gravitational mass movement in Austria and it is still operating. The system gradually evolved during the years of operation to maintain a reliable operation and to take new developments of information and communication technology (ICT) into account. This included the change from radio communication to UTMS and continuous maintenance of the hardware (revision of GNSS stations, revision of solar collectors, exchange of batteries) as well as software maintenance (Firmware updates of GNSS receivers, software updates, change to new operating systems). Especially the constant changes in the used software system results in maintenance time, which is often underestimated. From these experiences we derive lessons learned which can be a guideline for other long-term GNSS based monitoring systems.