{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2024,9,1]],"date-time":"2024-09-01T05:09:47Z","timestamp":1725167387245},"reference-count":44,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2018,7,22]],"date-time":"2018-07-22T00:00:00Z","timestamp":1532217600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41574023, 41622401 and 41731069"],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Scientific and Technological Innovation Plan from Shanghai Science and Technology Committee","award":["17511109501, 17DZ1100802 and 17DZ1100902"]},{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2016YFB0501802"],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"In Global Navigation Satellite System (GNSS) positioning, observation precisions are frequently impacted by the site-specific unmodeled errors, especially for the code observations that are widely used by smart phones and vehicles in urban environments. The site-specific unmodeled errors mainly refer to the multipath and other space loss caused by the signal propagation (e.g., non-line-of-sight reception). As usual, the observation precisions are estimated by the weighting function in a stochastic model. Only once the realistic weighting function is applied can we obtain the precise positioning results. Unfortunately, the existing weighting schemes do not fully take these site-specific unmodeled effects into account. Specifically, the traditional weighting models indirectly and partly reflect, or even simply ignore, these unmodeled effects. In this paper, we propose a real-time adaptive weighting model to mitigate the site-specific unmodeled errors of code observations. This unmodeled-error-weighted model takes full advantages of satellite elevation angle and carrier-to-noise power density ratio (C\/N0). In detail, elevation is taken as a fundamental part of the proposed model, then C\/N0 is applied to estimate the precision of site-specific unmodeled errors. The principle of the second part is that the measured C\/N0 will deviate from the nominal values when the signal distortions are severe. Specifically, the template functions of C\/N0 and its precision, which can estimate the nominal values, are applied to adaptively adjust the precision of site-specific unmodeled errors. The proposed method is tested in single-point positioning (SPP) and code real-time differenced (RTD) positioning by static and kinematic datasets. Results indicate that the adaptive model is superior to the equal-weight, elevation and C\/N0 models. Compared with these traditional approaches, the accuracy of SPP and RTD solutions are improved by 35.1% and 17.6% on average in the dense high-rise building group, as well as 11.4% and 11.9% on average in the urban-forested area. This demonstrates the benefit to code-based positioning brought by a real-time adaptive weighting model as it can mitigate the impacts of site-specific unmodeled errors and improve the positioning accuracy.<\/jats:p>","DOI":"10.3390\/rs10071157","type":"journal-article","created":{"date-parts":[[2018,7,24]],"date-time":"2018-07-24T06:58:56Z","timestamp":1532415536000},"page":"1157","source":"Crossref","is-referenced-by-count":40,"title":["Site-Specific Unmodeled Error Mitigation for GNSS Positioning in Urban Environments Using a Real-Time Adaptive Weighting Model"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"http:\/\/orcid.org\/0000-0002-0565-2038","authenticated-orcid":false,"given":"Zhetao","family":"Zhang","sequence":"first","affiliation":[{"name":"College of Surveying and GeoInformatics, Tongji University, Shanghai 200092, China"},{"name":"Department of Geomatics Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada"}]},{"ORCID":"http:\/\/orcid.org\/0000-0002-9553-4106","authenticated-orcid":false,"given":"Bofeng","family":"Li","sequence":"additional","affiliation":[{"name":"College of Surveying and GeoInformatics, Tongji University, Shanghai 200092, China"}]},{"given":"Yunzhong","family":"Shen","sequence":"additional","affiliation":[{"name":"College of Surveying and GeoInformatics, Tongji University, Shanghai 200092, China"}]},{"ORCID":"http:\/\/orcid.org\/0000-0002-6449-6696","authenticated-orcid":false,"given":"Yang","family":"Gao","sequence":"additional","affiliation":[{"name":"Department of Geomatics Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada"}]},{"given":"Miaomiao","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Surveying and GeoInformatics, Tongji University, Shanghai 200092, China"}]}],"member":"1968","published-online":{"date-parts":[[2018,7,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Li, T., Zhang, H., Gao, Z., Chen, Q., and Niu, X. 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