# metadata.dc.description[].value
NRCan provides GPS solutions that enable clients to obtain consistent cm-level positioning in the Canadian Spatial Reference System. Clients will benefit from the addition of the European Galileo constellation through increased reliability and improved accuracy. Oneparticularity of the Galileo system is that it broadcasts signals on four frequencies, as opposed to three frequencies for the modernized GPS satellites. This investigation shows that using all available frequencies is key for obtaining fast centimeter-level positioning.

# metadata.dc.description[].value
RNCan fourni des solutions GPS à ses clients pour l'obtention de coordonnées consistantes au cm avec le Système de référence spatial canadien. Les clients peuvent bénéficier de l'addition de la constellation Européenne Galileo par une meilleure fiabilité et une meilleureexactitude de positionnement. Une caractéristique du système Galiléo est la transmission des signaux sur quatre fréquences, comparativement à trois fréquences pour les satellites GPS modernes. Cette étude démontre que l'utilisation de cette quatrième fréquence joue un rôle important pour l'obtentionrapide d'une position centimétrique.

# metadata.dc.description.abstract[].value
GNSS modernization is a key component for reducing the convergence time of PPP solutions. Combining multiple constellations strengthens the geometry and using multiple frequencies allows for improved ambiguity resolution performance. In particular, tracking of the E6Galileo commercial service signal provides access to four frequencies which turns out to be beneficial in terms of instantaneous positioning capabilities. It was demonstrated that three linear combinations of ambiguities can be instantaneously resolved on Galileo satellites, leading to a rangeestimate approximately 5 times better than code measurements. This characteristic can enable instantaneous 3D positioning around 20 cm under good satellite geometry.Using data collected over Australia, phase biases on all frequencies were estimated for the Galileo satellites. These biases were used at the user end to compute PPP solutions. The latter confirmed the theoretical claims that widelane ambiguities could reliably be fixed with a single epoch of datausing a bootstrapping technique making use of the full ambiguity covariance matrix. A more sophisticated ambiguity estimation strategy termed BIE was subsequently used to demonstrate that instantaneous centimeter-level PPP is currently achievable by combining GPS and Galileo signals.It can be expected that the robustness and accuracy of the optimal estimation using uncombined four-frequency signals (OEUFS) strategy will improve in the future, with the increasing number of multi-frequency satellites and ground stations. Specifically, the fourth frequencies on BeiDou and QZSSwill enhance the geometry of the solution and will expedite convergence times. Within a few years, instantaneous PPP might very well replace RTK for a wide range of applications.

# metadata.dc.subject.other[].value
global navigation satellite systems (GNSS)