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Determination of precise Galileo orbits using combined GNSS and SLR observations / Grzegorz Bury in GPS solutions, vol 25 n° 1 (January 2021)  

Public [article]  inGPS solutions > vol 25 n° 1 (January 2021) . - n° 11 Titre : Determination of precise Galileo orbits using combined GNSS and SLR observations Type de document : Article/Communication Auteurs : Grzegorz Bury, Auteur ; Krzysztof Sosnica, Auteur ; Radoslaw Zajdel, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 11 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes descripteurs IGN] données TLS (télémétrie) [Termes descripteurs IGN] Galileo [Termes descripteurs IGN] International Terrestrial Reference Frame [Termes descripteurs IGN] orbite précise [Termes descripteurs IGN] orbitographie [Termes descripteurs IGN] pondération [Termes descripteurs IGN] positionnement par GNSS Résumé : (auteur) Galileo satellites are equipped with laser retroreflector arrays for satellite laser ranging (SLR). In this study, we develop a methodology for the GNSS-SLR combination at the normal equation level with three different weighting strategies and evaluate the impact of laser observations on the determined Galileo orbits. We provide the optimum weighting scheme for precise orbit determination employing the co-location onboard Galileo. The combined GNSS-SLR solution diminishes the semimajor axis formal error by up to 62%, as well as reduces the dependency between values of formal errors and the elevation of the Sun above the orbital plane—the β angle. In the combined solution, the standard deviation of the SLR residuals decreases from 36.1 to 29.6 mm for Galileo-IOV satellites and |β|> 60°, when compared to GNSS-only solutions. Moreover, the bias of the Length-of-Day parameter is 20% lower for the combined solution when compared to the microwave one. As a result, the combination of GNSS and SLR observations provides promising results for future co-locations onboard the Galileo satellites for the orbit determination, realization of the terrestrial reference frames, and deriving geodetic parameters. Numéro de notice : A2021-008 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-01045-3 date de publication en ligne : 31/10/2020 En ligne : https://doi.org/10.1007/s10291-020-01045-3 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96298 [article]

GLONASS FDMA data for RTK positioning: a five-system analysis / Andreas Brack in GPS solutions, vol 25 n° 1 (January 2021)  

Public [article]  inGPS solutions > vol 25 n° 1 (January 2021) . - n° 9 Titre : GLONASS FDMA data for RTK positioning: a five-system analysis Type de document : Article/Communication Auteurs : Andreas Brack, Auteur ; Benjamin Männel, Auteur ; Harald Schuh, Auteur Année de publication : 2021 Article en page(s) : n° 9 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] ambiguïté entière [Termes descripteurs IGN] CDMA [Termes descripteurs IGN] fréquence [Termes descripteurs IGN] modèle ionosphérique [Termes descripteurs IGN] positionnement cinématique en temps réel [Termes descripteurs IGN] positionnement par GNSS [Termes descripteurs IGN] résolution d'ambiguïté [Termes descripteurs IGN] satellite GLONASS [Termes descripteurs IGN] signal GLONASS Résumé : (auteur) The use of the GLONASS legacy signals for real-time kinematic positioning is considered. Due to the FDMA multiplexing scheme, the conventional CDMA observation model has to be modified to restore the integer estimability of the ambiguities. This modification has a strong impact on positioning capabilities. In particular, the ambiguity resolution performance of this model is clearly weaker than for CDMA systems, so that fast and reliable full ambiguity resolution is usually not feasible for standalone GLONASS, and adding GLONASS data in a multi-GNSS approach can reduce the ambiguity resolution performance of the combined model. Partial ambiguity resolution was demonstrated to be a suitable tool to overcome this weakness (Teunissen in GPS Solut 23(4):100, 2019). We provide an exhaustive formal analysis of the positioning precision and ambiguity resolution capabilities for short, medium, and long baselines in a multi-GNSS environment with GPS, Galileo, BeiDou, QZSS, and GLONASS. Simulations are used to show that with a difference test-based partial ambiguity resolution method, adding GLONASS data improves the positioning performance in all considered cases. Real data from different baselines are used to verify these findings. When using all five available systems, instantaneous centimeter-level positioning is possible on an 88.5 km baseline with the ionosphere weighted model, and on average, only 3.27 epochs are required for a long baseline with the ionosphere float model, thereby enabling near instantaneous solutions. Numéro de notice : A2021-009 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-01043-5 date de publication en ligne : 24/10/2020 En ligne : https://doi.org/10.1007/s10291-020-01043-5 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96299 [article]

CORS usage for GPS survey in the greater accra region: Advantages, limitation, and suggested remedies / Sebastian Botsyo in Journal of Geovisualization and Spatial Analysis, vol 4 n° 2 (December 2020)  

Public [article]  inJournal of Geovisualization and Spatial Analysis > vol 4 n° 2 (December 2020) . - n° 20 Titre : CORS usage for GPS survey in the greater accra region: Advantages, limitation, and suggested remedies Type de document : Article/Communication Auteurs : Sebastian Botsyo, Auteur ; Bernard Borketey Bortei, Auteur ; John Ayer, Auteur Année de publication : 2020 Article en page(s) : n° 20 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes descripteurs IGN] balise [Termes descripteurs IGN] géopositionnement [Termes descripteurs IGN] Ghana [Termes descripteurs IGN] International Terrestrial Reference Frame [Termes descripteurs IGN] positionnement statique [Termes descripteurs IGN] station de référence [Termes descripteurs IGN] système de référence local Résumé : (auteur) The use of Continuously Operating Reference Stations (CORS) enables surveyors to differentially correct static Global Positioning System (GPS) measurements. CORS are designed to support the broad spectrum of post-processed, relative GPS techniques, and applications. Enhancing geospatial positioning applications of CORS data involves the critical role in defining the nation’s geodetic reference system. With the establishment of a coordinated system of CORS, an Online Positioning User Service can become available for processing in single positioning mode to provide corresponding accurate and homogeneous positional coordinates. The Survey and Mapping Division (SMD), Lands Commission of Ghana, has established four CORS in the Greater Accra, and Ashanti, Western and Brong-Ahafo Regions, respectively, to provide a basic CORS network in accordance with the International Terrestrial Reference Frame (ITRF). However, most surveyors continue to reference their works in these regions to ground survey beacons that have been coordinated and adjusted by variable survey methods. This obviously makes homogeneity of data unpredictable. This study explored the extent of usage of existing CORS network established by SMD with particular focus on the CORS in the Greater Accra Region for GPS surveys and to determine its usefulness in ensuring homogeneity in GPS data collection. The professional participatory (interviews) technique was coupled with differential GPS field observations with the CORS as reference in one case and ground control stations as reference in the other in making relatively conclusive analysis. Test results showed that GPS field survey of an approximate range of 23 km away from the Accra CORS yielded an average positional change in Northings and Eastings of − 0.790 m, − 0.176 m and − 0.681 m, − 0.098 m for single and dual frequency, respectively, in different localities within the study area. Beyond a range of 25 km from the Accra CORS, the average positional change in Northings and Eastings are − 0.536 m, − 0.007 m and − 1.370 m, 0.334 m for single and dual frequency respectively. Of 128 geomatic professionals interviewed, 39% are aware of the availability of COR stations in Greater Accra, 61% are unaware, and 28% are aware and users of the Accra CORS whereas 11% are aware but non-users of the Accra COR station. Of all users sampled, 17.5% are regular and frequent users of the Accra COR station and 10.5% are occasional or seldom users. The results show that the Accra CORS is vital to ensuring a uniform homogenous GPS data. However, very few people are using it due to low public awareness of the usefulness of the CORS among professional surveyors and other users and a cumbersome, bureaucratic nature in CORS data acquisition for post-processing and RTK GPS surveys. Numéro de notice : A2020-723 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s41651-020-00061-8 date de publication en ligne : 11/09/2020 En ligne : https://doi.org/10.1007/s41651-020-00061-8 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96324 [article]

Exploring the heterogeneity of human urban movements using geo-tagged tweets / Ding Ma in International journal of geographical information science IJGIS, vol 34 n° 12 (December 2020)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 34 n° 12 (December 2020) . - pp 2475 -2 496 Titre : Exploring the heterogeneity of human urban movements using geo-tagged tweets Type de document : Article/Communication Auteurs : Ding Ma, Auteur ; Toshihiro Osaragi, Auteur ; Takuya Oki, Auteur ; Bin Jiang, Auteur Année de publication : 2020 Article en page(s) : pp 2475 -2 496 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes descripteurs IGN] analyse spatio-temporelle [Termes descripteurs IGN] données issues des réseaux sociaux [Termes descripteurs IGN] données localisées des bénévoles [Termes descripteurs IGN] espace urbain [Termes descripteurs IGN] flux de données [Termes descripteurs IGN] géoétiquetage [Termes descripteurs IGN] géolocalisation [Termes descripteurs IGN] hétérogénéité [Termes descripteurs IGN] Londres [Termes descripteurs IGN] migration humaine [Termes descripteurs IGN] modèle de simulation [Termes descripteurs IGN] modèle orienté agent [Termes descripteurs IGN] population urbaine [Termes descripteurs IGN] Tokyo (Japon) [Termes descripteurs IGN] Twitter Résumé : (auteur) The availability of vast amounts of location-based data from social media platforms such as Twitter has enabled us to look deeply into the dynamics of human movement. The aim of this paper is to leverage a large collection of geo-tagged tweets and the street networks of two major metropolitan areas—London and Tokyo—to explore the underlying mechanism that determines the heterogeneity of human mobility patterns. For the two target cities, hundreds of thousands of tweet locations and road segments were processed to generate city hotspots and natural streets. User movement trajectories and city hotspots were then used to build a hotspot network capable of quantitatively characterizing the heterogeneous movement patterns of people within the cities. To emulate observed movement patterns, the study conducts a two-level agent-based simulation that includes random walks through the hotspot networks and movements in the street networks using each of three distance types—metric, angular and combined. Comparisons of the simulated and observed movement flows at the segment and street levels show that the heterogeneity of human urban movements at the collective level is mainly shaped by the scaling structure of the urban space. Numéro de notice : A2020-692 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2020.1718153 date de publication en ligne : 24/01/2020 En ligne : https://doi.org/10.1080/13658816.2020.1718153 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96233 [article]

A generic framework for improving the geopositioning accuracy of multi-source optical and SAR imagery / Niangang Jiao in ISPRS Journal of photogrammetry and remote sensing, vol 169 (November 2020)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 169 (November 2020) . - pp 377 - 388 Titre : A generic framework for improving the geopositioning accuracy of multi-source optical and SAR imagery Type de document : Article/Communication Auteurs : Niangang Jiao, Auteur ; Feng Wang, Auteur ; Hongjian You, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : pp 377 - 388 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image mixte [Termes descripteurs IGN] chaîne de traitement [Termes descripteurs IGN] correction géométrique [Termes descripteurs IGN] étalonnage géométrique [Termes descripteurs IGN] géolocalisation [Termes descripteurs IGN] image Gaofen [Termes descripteurs IGN] image Jilin [Termes descripteurs IGN] image optique [Termes descripteurs IGN] image radar moirée [Termes descripteurs IGN] image satellite [Termes descripteurs IGN] point d'appui [Termes descripteurs IGN] précision géométrique (imagerie) Résumé : (auteur) To date, numerous Earth observation datasets from different types of satellites have been widely used in photogrammetric fields, including urban 3D modelling and geographic information systems. The development of small satellites has provided a new way to obtain repeated observations in a short period. However, compared with that of standard satellite imagery, the geometric performance of imagery from small satellites is relatively poor, restricting their photogrammetric applications. Traditional methods can improve the accuracy of optical images with the addition of well-distributed ground control points (GCPs), which require considerable financial and human resources. The collection of multi-view datasets is an alternative method for geometric processing without GCPs, but relies heavily on the stability and revisit period of satellite platforms. Therefore, this paper presents a framework for improving the geopositioning accuracy of multi-source datasets obtained from optical and synthetic aperture radar (SAR) satellites, and a novel heterogeneous weight strategy is proposed based on an analysis of the geometric error sources of SAR and optical images. The geometric performance of multi-source optical imagery from the Jilin-1 (JL-1) small satellite constellation is evaluated and analysed first, and then Gaofen-3 (GF-3) SAR images are calibrated based on statistical analysis for the production of virtual control points (VCPs). Based on our proposed heterogeneous weight strategy, multi-source optical and SAR images are integrated to improve the geopositioning accuracy. Experimental results indicate that our proposed model can achieve the best performance compared with other popular models, producing an accuracy of approximately 3 m in planimetry and 2 m in height, thereby providing a generic way to synergistically use multi-source remote sensing data. Numéro de notice : A2020-642 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2020.09.017 date de publication en ligne : 12/10/2020 En ligne : https://doi.org/10.1016/j.isprsjprs.2020.09.017 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96066 [article]

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Evolution of orbit and clock quality for real-time multi-GNSS solutions / Kamil Kazmierski in GPS solutions, Vol 24 n° 4 (October 2020)  

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Integer-estimable GLONASS FDMA model as applied to Kalman-filter-based short- to long-baseline RTK positioning / Pengyu Hou in GPS solutions, Vol 24 n° 4 (October 2020)  

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A LiDAR aiding ambiguity resolution method using fuzzy one-to-many feature matching / Chuang Qian in Journal of geodesy, vol 94 n° 10 (October 2020)  

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Machine‐learning prediction models for pedestrian traffic flow levels: Towards optimizing walking routes for blind pedestrians / Achituv Cohen in Transactions in GIS, Vol 24 n° 5 (October 2020)  

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A multi-frequency and multi-GNSS method for the retrieval of the ionospheric TEC and intraday variability of receiver DCBs / Min Li in Journal of geodesy, vol 94 n° 10 (October 2020)  

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Prediction of RTK positioning integrity for journey planning / A. El-Mowafy in Journal of applied geodesy, vol 14 n° 4 (October 2020)  

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An offshore real-time precise point positioning technique based on a single set of BeiDou short-message communication devices / Zhixi Nie in Journal of geodesy, vol 94 n° 9 (September 2020)  

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Comparing pedestrians’ gaze behavior in desktop and in real environments / Weihua Dong in Cartography and Geographic Information Science, Vol 47 n° 5 (September 2020)  

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GNSS scale determination using calibrated receiver and Galileo satellite antenna patterns / Arturo Villiger in Journal of geodesy, vol 94 n° 9 (September 2020)  

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