GNSS is the abbreviation for Global Navigation Satellite Systems and includes:
BeiDou constellation also contains with inclined geosynchronous orbiting (IGSO) and geostationary satellites (GEO) as a regional component supporting navigation applications in the Asian region. There are also some other systems dedicated to regional applications:
The principle of GNSS measurements is explained here.
AIUB is part of the Center for Orbit Determination in Europe (CODE) consortium. As such, the research conducted at AIUB in the field of GNSS data processing and modelling is driven by the activities of the CODE analysis center for the International GNSS Service (IGS). Some of the projects and selected results are introduced in the subsequent pages: