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Improving smartphone-based GNSS positioning using state space augmentation techniques / Francesco Darugna (2021)
Titre : Improving smartphone-based GNSS positioning using state space augmentation techniques Type de document : Thèse/HDR Auteurs : Francesco Darugna, Auteur ; Steffen Schön, Directeur de thèse Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2021 Collection : DGK - C, ISSN 0065-5325 num. 864 Importance : 189 p. Note générale : bibliographie
Diese Arbeit ist gleichzeitig veröffentlicht in:Wissenschaftliche Arbeiten der Fachrichtung Geodäsie und Geoinformatik der Universität Hannover - ISSN 0174-1454, Nr. 368, Hannover 2021Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] antenne GNSS
[Termes IGN] étalonnage d'instrument
[Termes IGN] positionnement par GNSS
[Termes IGN] retard troposphérique zénithal
[Termes IGN] téléphone intelligentRésumé : (auteur) Low-cost receivers providing Global Navigation Satellite System (GNSS) pseudorange and carrier phase raw measurements for multiple frequencies and multiple GNSS constellations have become available on the market in the last years. This significantly has increased the number of devices equipped with the necessary sensors to perform precise GNSS positioning. GNSS pseudorange and carrier phase are used to compute user positions. While both observations are affected by different error sources, e.g. the passage through the atmosphere, only the carrier-phase has an ambiguous nature. The resolution of this ambiguity is a crucial factor to reach fast and highly precise GNSS-based positioning. Currently, several smartphones are equipped with a dual-frequency, multi-constellation receiver. The access to Android-based GNSS raw measurements has become a strong motivation to investigate the feasibility of smartphone-based high-accuracy positioning. The quality of smartphone GNSS measurements has been analyzed, suggesting that they often suffer from low signal-to-noise, inhomogeneous antenna gain and high levels of multipath. This workshows how to tackle several of the currently present obstacles and demonstrates centimeter-level positioning with a low-cost GNSS antenna and a low-cost GNSS receiver built into an off-the-shelf smartphone. Since the beginning of the research in smartphone-based positioning, the device’s GNSS antenna has been recognized as one of the main limitations. Besides Multipath (MP), the antenna radiation pattern is the main site-dependent error source of GNSS observations. An absolute antenna calibration has been performed for the dual-frequency smartphone HuaweiMate20X. Antenna Phase Center Offset (PCO), and Variations (PCV ) have been estimated to correct for the antenna impact on the L1 and L5 phase observations. Accordingly, the relevance of considering the individual PCO and PCV for the two frequencies is shown. The PCV patterns indicate absolute values up to 2 cm and 4 cm for L1 and L5, respectively. The impactof antenna corrections has been assessed in different multipath environments using a high-accuracy positioning algorithm employing an uncombined observation model and applying Ambiguity Resolution (AR). Experiments both in zero-baseline and short-baseline configurations have been performed. Instantaneous AR in the zero-baseline setup has been demonstrated, showing the potential for cm-level positioning with low-cost sensors available inside smartphones. In short-baselines configurations, no reliable AR is achieved without antenna corrections. However, after correcting for PCV, successful AR is demonstrated for a smartphone placed in a low multipath environment on the ground of a soccer field. For a rooftop open-skytest case with large multipath, AR was successful in 19 out of 35 data-sets. Overall, the antenna calibration is demonstrated being an asset for smartphone-based positioning with AR,showing cm-level 2D Root Mean Square Error (RMSE). In GNSS-based positioning, a user within a region covered by a network of reference stations can take advantage of the network-estimated augmentation parameters. Among the GNSS error sources, atmospheric delays have a strong impact on the positioning performance and the ability to resolve ambiguities. State Space Representation (SSR) atmospheric corrections, i.e. tropospheric and ionospheric delays, are commonly estimated for the approximate user position by interpolation from values calculated for the reference stations. Widely used interpolation techniques are Inverse Distance Weighted (IDW), Ordinary Kriging (OK)and Weighted Least Squares (WLS). The interpolation quality of such techniques during severe weather events and Traveling Ionospheric Disturbances (TIDs) is analyzed. To improve the interpolation performance during such events, modified WLS methods taking advantage of the physical atmospheric behavior are proposed. To support this interpolation approach, external information from Numerical Weather Models (NWM) for tropospheric interpolation and from TID modeling for ionospheric interpolation is introduced to the algorithms. The interpolation is assessed using simulated data (considering artificial and real network geometries), and real SSR parameters generated by network computation of GNSS measurements. As examples, two severe weather events in northern Europe in 2017 and one TID eventover Japan in 2019 have been analyzed. The interpolation of SSR Zenith Tropospheric Delay(ZTD) and ionospheric parameters is evaluated. Considering the reference station positions as rover locations, the modified WLS approach marks a lower RMSE in up to 80% of the cases during sharp weather fluctuations. Also, the average error can be decreased in 64% of the cases during the TID event investigated. Improvements up to factors larger than two are observed. Furthermore, specific cases are isolated, showing particular ZTD variations where significant errors (e.g. larger than 1 cm) can be reduced by up to 20% of the total amount. As a final product of the analysis, tropospheric and ionospheric messages are proposed. The messages contain the information needed to implement the suggested interpolation. Along with the need for accurate atmospheric models, the concept of consistency in the SSR corrections is crucial. A format that can transport all the SSR corrections estimated by a network is the Geo++ SSR format (SSRZ). Exploiting the features of the SSRZ format, the impact of an error in the transported ionospheric parameters is investigated. It is shown that the position estimation strongly depends on the ionospheric modeling and mismodeling can result in cm level errors, especially in the height component. Numéro de notice : 17182 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : Thesis : Geodäsie und Geoinformatik : Hanovre : 2021 En ligne : https://dgk.badw.de/fileadmin/user_upload/Files/DGK/docs/c-864.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98000 RTK and PPP-RTK using smartphones: From short-baseline to long-baseline applications / Francesco Darugna (2019)
Titre : RTK and PPP-RTK using smartphones: From short-baseline to long-baseline applications Type de document : Article/Communication Auteurs : Francesco Darugna, Auteur ; et al., Auteur Editeur : Alexandria : Institute of Navigation Année de publication : 2019 Conférence : ION GNSS+ 2019, 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation 01/09/2019 Miami Floride - Etats-Unis non OA proceedings Importance : pp 3932 - 3945 Format : 21 x 30 cm Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] bruit atmosphérique
[Termes IGN] correction du trajet multiple
[Termes IGN] ligne de base
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] positionnement ponctuel précis
[Termes IGN] précision centimétrique
[Termes IGN] téléphone intelligent
[Termes IGN] trajet multipleRésumé : (auteur) Low cost receivers providing GNSS code and phase raw measurements for multiple frequencies and multiple GNSS constellations have recently become available on the market. This significantly increases the number of devices equipped with the necessary sensors to perform precise GNSS positioning like Network-RTK or PPP. The smartphone GNSS measurements often suffer from low signal-to-noise, inhomogeneous antenna gain and high levels of multipath. Here, we show how to tackle several of currently present obstacles and demonstrate centimeter-level kinematic positioning with a low-cost GNSS antenna and a low-cost GNSS receiver built into an off-the-shelf smartphone. For some devices we found that the phase observations do not have integer characteristic but appear to have random biases. To some extend these observations can still be used in a “float”-type precise algorithm. Low cost GNSS sensors like the ones built into smartphones are generally used with antennas that have a uniform gain pattern and do not reject LHCP signals. Accordingly, strong multipath influence is observed in many applications. Experiments both in a zero-baseline and a short-baseline configuration have been performed, to evaluate the aforementioned biases and discontinuities. We demonstrate instantaneous ambiguity resolution in the zero-baseline setup, showing the potential for RTK-positioning with low-cost sensors available inside smartphones. Positioning with PPP-RTK or Network-RTK is more challenging because additional residual atmospheric noise is present. Experiments with different baseline lengths have been performed in different ionospheric conditions and the achieved accuracies are reported. Numéro de notice : C2019-040 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95376