I ricercatori dell’Area Space and Navigation Technologies, in collaborazione con i colleghi del Politecnico di Torino, hanno osservato dal punto di vista degli utilizzatori quello che è accaduto in questi giorni al sistema Galileo. Infatti il sistema di navigazione satellitare europeo ha affrontato dei problemi tecnici a livello globale.
Le osservazioni sono disponibili sul sito del NavSAS (www.navsas.eu), il gruppo di ricerca congiunto fra Politecnico di Torino e LINKS sulla navigazione satellitare.
In particolare, questo post www.navsas.eu/node/614 riassume quello che è stato osservato fra il 15 ed il 18 luglio.
The short-term behavior of the computed position has an interesting “snake-like” trend, suggesting a temporal correlation of the SIS induced error (no temporal correlation is introduced by the PVT solution algorithm used by the receiver), possibly in the form of a clock drift. The receiving antenna was fixed on our rooftop. The figure hereafter reports this observation (blue points: without carrier smoothing, red points: with carrier smoothing; the temporal correlation introduced by carrier smoothing is negligible with respect to the one brought by the SIS). By processing 4 minutes of GNSS signal taken at 09:10 UTC, our software receiver provided a severely biased position solution by means of a Least Mean Square (LMS) algorithm. The first estimation is located about 1158 meters from the georeferenced antenna, and the solutions are drifting towards the South-West direction. In particular, shifts of 21 m and 58 m on respectively E-W and N-S coordinates are experienced during the observation time. A comparison between non-smoothed and very-smoothed positioning solutions is shown in the figure. Even without the use of carrier-smoothing the sequence of estimations shows a remarkable level of correlation along the time. Nevertheless, it has to be remarked that Galileo is usable since December 2016, but its services are still in the Initial phase, and the full operation capability has not been declared yet.