The Impact of Low-Earth-Orbit Satellites on GNSS Ambiguity Resolution

In this thesis, the impact of low-earth-orbit (LEO) satellites on carrier phase ambiguity resolution is demonstrated through a global covariance simulation and a hardware in-the-loop simulation. Dedicated LEO constellations for GNSS are expected to become operational within the next few years and bring with them many changes to the GNSS industry. LEO satellites move much faster than MEO satellites and therefore will introduce more geometric variation, resulting in faster ambiguity resolution. The LEO constellation in this study is modelled after Iridium, a telecommunications constellation with 66 satellites orbiting at 780 km altitude. Iridium is not dense enough to operate standalone but was shown to be very effective to support GPS. The simulations were designed to isolate the LEO satellites, specifically their motion and their geometry, as the primary source of ambiguity resolution improvement. The covariance simulation tested 624 locations from the equator to the North pole to find that augmenting GPS with a LEO constellation resulted in reaching a 99.9% probability of correct fix an average of 2.4 times faster than GPS alone. Locations with high and low density are analyzed and the most impressive improvement was found in places with a small number of visible LEO satellites. The hardware in-the-loop simulation used a Spirent GSS7000 simulator, two NovAtel OEM7 receivers, and an open source GNSS processing tool to once again compare the speed of ambiguity resolution between GPS augmented with LEO satellites to GPS only. This simulation found a 22.4% improvement to reach a 99% probability of correct fix and a 29.1% improvement to reach a 99.9999% probability of correct fix. Both simulations were conducted using a single frequency, double differenced position solution with GPS and the LEO constellation. Based on these results, this thesis concluded that LEO GNSS will improve carrier phase ambiguity convergence speed due to the fast-changing geometry and increased observability of the LEO satellites. Additionally, this thesis will discuss some potential applications for LEO GNSS and the significance of this research. The results of both the covariance simulation and the hardware simulation suggest that the 66 simulated LEO satellites are enough to support MEO GNSS. The practicality, applications, and sustainability of LEO mega-constellations for GNSS is contended.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Engineering – Geomatics

Grantor dc:publisher.institution

Graduate Studies

Year dc:date.issued

2025

Author dc:creator

• Mah, Claire

Advisor dc:contributor.advisor

• O'Keefe, Kyle

Committee members dc:contributor.committeemember

• Yang, Hongzhou
• Detchev, Ivan
• O'Keefe, Kyle

• GNSS
• Navigation
• Positioning
• GPS
• Low-earth-orbit
• Ambiguity Resolution
• Simulation
• PNT

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

en

DOI

https://dx.doi.org/10.11575/PRISM/50419

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/122825