Satellite positioning problems in urban agglomerations

The article presents theoretical considerations and experimental results aimed at highlighting certain problems associated with the use of GNSS (Global Navigation Satellite Systems) in urban agglomerations. The first part of the article presents considerations regarding potential problems related to determining position coordinates in an environment with high-rise buildings, which are illustrated with literature examples. The second part presents the results of our own research regarding the availability of snapshot-type GNSS reliability monitoring methods (RAIM) in urban agglomerations. Numerical experiments were performed using proprietary software.The dynamic growth of GNSS applications, stimulated by the ease of obtaining object location data, miniaturization, and the low price of receivers, makes it necessary to ask about the limitations of satellite positioning in urban agglomerations. The question seems justified if we take into account that high buildings cause the blocking of satellite signals (thereby reducing the number of satellites tracked by the receiver) and reflect signals, which can lead to gross positioning errors. Both phenomena are dangerous. In the first case, a decrease in position accuracy may occur due to the deterioration of the space segment geometry (an increase in the geometric dilution of precision coefficients, also known as DOP). (…)