Analysis of Stability and Temperature Variations in SAPOS Reference Stations in Lower Saxonyand Adjacent Regions between 2017 and 2020

This study examines the stability and temperature variations of SAPOS reference stations across Lower Saxony and neighboring federal states over a four-year period (2017–2020). SAPOS, the Satellite Positioning Service of the German National Survey, provides high-precision geodetic
reference points essential for applications such as surveying, navigation, and geographic information systems (GIS). Data from 43 SAPOS stations in Lower Saxony, ten SAPOS stations in adjacent regions, and 54 German Weather Service (DWD) stations were analysed using custom programs in Python
and MATLAB. The findings demonstrate the high SAPOS availability and station quality, though systematic effects were identified in the cleaned time series of topocentric coordinates for certain stations. These effects relate to multipath sensitivity, assessed using the Multipath Indicator (MPI),
which reflects signal reflection interference, confirming the high quality of SAPOS stations. The study corrected these effects via drift and offset adjustments and outlier removal. The analysis investigated five categories of deviations, revealing recurring patterns influenced by station type and installation characteristics. Notably, unilateral solar exposure and temperature fluctuations at the Braunschweig station caused deviations of up to 5 mm in the north and east components of topocentric coordinates.