Over the past years, there has been an increase in number of Global Navigation Satellite Systems (GNSSs). Some of these GNSS are already in service, but some of them still under development. As a result of developing these systems by different countries spread through different continents, users will soon be overwhelmed by lists of concepts, features, and idioms, which are announced by differen...

The Bureau International des Poids et Mesures (BIPM) is in charge of producing International Atomic Time TAI. In this aim, it uses clock data from more than 60 laboratories spread worldwide. For two decades, GPS has been an essential tool to link these clocks, and products from the International GNSS Service (IGS) have been used to improve the quality of these time links since its creation in t...

This article presents signal processing algorithms used as a new remote sensing tool, that is passive bistatic SAR with navigation satellites (e.g. GPS, GLONASS or Galileo) as transmitters of opportunity. Signal synchronisation and image formation algorithms are described for two system variants: one where the receiver is moving and one where it is fixed on the ground. The applicability and fun...

Nowadays, the Global Navigation Satellite Systems (GNSS), working like global positioning systems, are the GPS and the GLONASS. They are based on a newtonian model and hence they are only operative when several relativistic effects are corrected. The most important relativistic effects (to order 1/c 2) are: the Einstein effect or gravitational violet shift of the frequency of the clock of the s...

j a n u a r y / f e b r u a r y 2 0 1 1 www.insidegnss.com In satellite navigation, a GNSS receiver must account for several sources of error such as relativistic effects, atmospheric propagation delay, offset of satellite clocks from system time and satellite ephemeris. In order to accurately compute user position, velocity, and time (PVT), these errors need to be predicted/estimated precisely...

Precision is a quest on which travelers journey halfway to their destination, and then halfway again and again and again, never reaching finality.