{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T09:10:37Z","timestamp":1783933837938,"version":"3.55.0"},"reference-count":45,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T00:00:00Z","timestamp":1783900800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Integrating low Earth orbit (LEO) satellites into GNSS (Global Navigation Satellite System) MEO (Medium Earth Orbit) constellations enhances global positioning but faces technical bottlenecks. Through a 1D vehicular scenario simulation using MATLAB-based stochastic modeling of error sources and Least Squares estimation, MEO, LEO and hybrid configurations are evaluated, accounting for ionospheric, atmospheric and multipath errors. Results show that a single LEO satellite fails to improve accuracy due to the absence of onboard atomic clocks and the limitations of using Two-Line Elements (TLEs). However, a threshold of three LEO satellites significantly reduces positioning errors by approximately 35% through effective error averaging. The findings demonstrate that transitioning from TLEs to Precise Orbit Determination (POD) and clock stability are essential for LEO augmentation. These results provide an analytical framework for resilient PNT (Positioning, Navigation and Timing) applications, including autonomous driving and smart cities.<\/jats:p>","DOI":"10.3390\/s26144434","type":"journal-article","created":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T08:53:58Z","timestamp":1783932838000},"page":"4434","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Characterization of Pseudorange Errors in Hybrid LEO\/MEO PNT System"],"prefix":"10.3390","volume":"26","author":[{"given":"Andrea","family":"Bianconi","sequence":"first","affiliation":[{"name":"Department of Information Engineering, University of Florence, 50139 Florence, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2510-395X","authenticated-orcid":false,"given":"Omar","family":"Morandi","sequence":"additional","affiliation":[{"name":"Department of Mathematics and Computer Science, University of Florence, 50139 Florence, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0145-8406","authenticated-orcid":false,"given":"Simone","family":"Morosi","sequence":"additional","affiliation":[{"name":"Department of Information Engineering, University of Florence, 50139 Florence, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5520-7322","authenticated-orcid":false,"given":"Marco","family":"Dolfi","sequence":"additional","affiliation":[{"name":"Department of Information Engineering, University of Florence, 50139 Florence, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Prol, F.S., Kaasalainen, S., Lohan, E.S., Bhuiyan, M.Z.H., Praks, J., and Kuusniemi, H. 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