# name
GLONASS ionosphere-free ambiguity resolution for precise point positioning

# 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 GLONASS and Galileo constellations through increased reliability and improved accuracy. However, useof different satellite constellations and receiver types presents many signal processing challenges to ensure full consistency and realize the cumulative benefits of these systems. Signal biases are a notable concern for the GLONASS constellation and careful treatment is necessary. Thisinvestigation reports on a novel method to mitigate the impacts of such biases, resulting in simplified processing of data from mixed receiver types and firmware versions.

# 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 des constellations GLONASS et Galileo par une meilleure fiabilité et une meilleureexactitude de positionnement. Cependant, l'utilisation de différentes constellations et types de récepteur présente plusieurs défis de traitement pour assurer leur compatibilité et réaliser les bénéfices anticipés de tels systèmes. Les biais de signaux de la constellation GLONASS constituent l'un deces défis pour lesquels un traitement particulier est nécessaire. Cette étude démontre une nouvelle méthode qui simplifie le traitement de ces biais indépendamment du type de récepteur ou de la version de son micro-logiciel.

# metadata.dc.description.abstract[].value
Current GLONASS satellites transmit signals based on the frequency division multiple access (FDMA) technology. Due to frequency-dependent equipment delays occurring within GNSS receivers, GLONASS carrier-phase and code observations are contaminated by inter-frequencybiases. As a consequence, GLONASS ambiguity parameters in long-baseline processing are typically estimated as float values. In this paper, a strategy is investigated which benefits from the frequency spacing of GLONASS frequencies on the L1 and L2 bands, allowing for an ionosphere-free ambiguitywith a wavelength of approximately 5 cm to be defined, therefore avoiding the problematic widelane ambiguity resolution. Based on 12 independent baselines with a mean inter-station distance of about 850 km over a one-week period, it is demonstrated that close to 95% of the estimateddouble-differenced ionosphere-free ambiguities are within 0.15 cycles of an integer, thereby suggesting that long-baseline ambiguity resolution can be achieved for GLONASS. Applying between-station ambiguity constraints in precise point positioning (PPP) solutions was found to improve longitudinalrepeatability in static mode by approximately 20% for sessions between 2 to 6 hours in duration. In kinematic mode, only limited improvements were made since the short wavelength of GLONASS ionosphere-free ambiguities requires the solution to be nearly converged before successful ambiguityresolution can be achieved.

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

# metadata.dc.title[].value
GLONASS ionosphere-free ambiguity resolution for precise point positioning