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Rapid re-convergences to ambiguity-fixed solutions in precise point positioning / J. Geng in Journal of geodesy, vol 84 n° 12 (December 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 12 (December 2010) . - 10 p. ; pp 705 - 714 Titre : Rapid re-convergences to ambiguity-fixed solutions in precise point positioning Type de document : Article/Communication Auteurs : J. Geng, Auteur ; X. Meng, Auteur ; A. Dodson, Auteur ; et al., Auteur Année de publication : 2010 Article en page(s) : 10 p. ; pp 705 - 714 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] ambiguïté entière [Termes IGN] convergence [Termes IGN] correction ionosphérique [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] propagation ionosphérique [Termes IGN] résolution d'ambiguïté [Termes IGN] Suisse [Termes IGN] temps réel Résumé : (Auteur) Integer ambiguity resolution at a single receiver can be achieved if the fractional-cycle biases are separated from the ambiguity estimates in precise point positioning (PPP). Despite the improved positioning accuracy by such integer resolution, the convergence to an ambiguity-fixed solution normally requires a few tens of minutes. Even worse, these convergences can repeatedly occur on the occasion of loss of tracking locks for many satellites if an open sky-view is not constantly available, consequently totally destroying the practicability of real-time PPP. In this study, in case of such re-convergences, we develop a method in which ionospheric delays are precisely predicted to significantly accelerate the integer ambiguity resolution. The effectiveness of this method consists in two aspects: first, wide-lane ambiguities can be rapidly resolved using the ionosphere-corrected wide-lane measurements, instead of the noisy Melbourne–Wübbena combination measurements; second, narrow-lane ambiguity resolution can be accelerated under the tight constraints derived from the ionosphere-corrected unambiguous wide-lane measurements. In the test at 90 static stations suffering from simulated total loss of tracking locks, 93.3 and 95.0% of re-convergences to wide-lane and narrow-lane ambiguity resolutions can be achieved within five epochs of 1-Hz measurements, respectively, even though the time latency for the predicted ionospheric delays is up to 180 s. In the test at a mobile van moving in a GPS-adverse environment where satellite number significantly decreases and cycle slips frequently occur, only when the predicted ionospheric delays are applied can the rate of ambiguity-fixed epochs be dramatically improved from 7.7 to 93.6% of all epochs. Therefore, this method can potentially relieve the unrealistic requirement of a continuous open sky-view by most PPP applications and improve the practicability of real-time PPP. Numéro de notice : A2010-558 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0404-4 Date de publication en ligne : 14/08/2010 En ligne : https://doi.org/10.1007/s00190-010-0404-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30750 [article]

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266-2010121	SL	Revue	Centre de documentation	Revues en salle	Disponible

Integer ambiguity resolution in precise point positionning : method comparison / J. Geng in Journal of geodesy, vol 84 n° 9 (September 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 9 (September 2010) . - pp 569 - 581 Titre : Integer ambiguity resolution in precise point positionning : method comparison Type de document : Article/Communication Auteurs : J. Geng, Auteur ; X. Meng, Auteur ; A. Dodson, Auteur ; Felix Norman Teferle, Auteur Année de publication : 2010 Article en page(s) : pp 569 - 581 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] analyse comparative [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] précision millimétrique [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) Integer ambiguity resolution at a single receiver can be implemented by applying improved satellite products where the fractional-cycle biases (FCBs) have been separated from the integer ambiguities in a network solution. One method to achieve these products is to estimate the FCBs by averaging the fractional parts of the float ambiguity estimates, and the other is to estimate the integer-recovery clocks by fixing the undifferenced ambiguities to integers in advance. In this paper, we theoretically prove the equivalence of the ambiguity-fixed position estimates derived from these two methods by assuming that the FCBs are hardware-dependent and only they are assimilated into the clocks and ambiguities. To verify this equivalence, we implement both methods in the Position and Navigation Data Analyst software to process 1 year of GPS data from a global network of about 350 stations. The mean biases between all daily position estimates derived from these two methods are only 0.2, 0.1 and 0.0 mm, whereas the standard deviations of all position differences are only 1.3, 0.8 and 2.0 mm for the East, North and Up components, respectively. Moreover, the differences of the position repeatabilities are below 0.2 mm on average for all three components. The RMS of the position estimates minus those from the International GNSS Service weekly solutions for the former method differs by below 0.1 mm on average for each component from that for the latter method. Therefore, considering the recognized millimeter-level precision of current GPS-derived daily positions, these statistics empirically demonstrate the theoretical equivalence of the ambiguity-fixed position estimates derived from these two methods. In practice, we note that the former method is compatible with current official clock-generation methods, whereas the latter method is not, but can potentially lead to slightly better positioning quality. Numéro de notice : A2010-416 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0399-x Date de publication en ligne : 06/08/2010 En ligne : https://doi.org/10.1007/s00190-010-0399-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30609 [article]

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Ubiquitous positioning: Anyone, anything, anytime, anywhere / X. Meng in GPS world, vol 18 n° 6 (June 2007)

Public [article]  inGPS world > vol 18 n° 6 (June 2007) . - pp 60 - 65 Titre : Ubiquitous positioning: Anyone, anything, anytime, anywhere Type de document : Article/Communication Auteurs : X. Meng, Auteur ; A. Dodson, Auteur ; T. Moore, Auteur ; G. Roberts, Auteur Année de publication : 2007 Article en page(s) : pp 60 - 65 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] caméra numérique [Termes IGN] GPS assisté pour la navigation (technologies) [Termes IGN] GPS-INS [Termes IGN] PDA [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GNSS [Termes IGN] positionnement par GPS [Termes IGN] récepteur GPS [Termes IGN] téléphonie mobile Résumé : (Auteur) Mark Weiser is not exactly a household name. He was a chief technology officer at the Xerox Corporation's famous Palo Alto Research Center. This is the same outfit which brought us laser printing, Ethernet communications, the graphical user interface paradigm (including the mouse), and object-oriented programming. Like many of those who make a significant difference in technical fields, Mark Weiser's contributions are well known but his name is not. Dr. Weiser introduced the concept of "ubiquitous computing." He coined this term in 1988 to describe a new generation of the computer era, where the first two generations, that of the mainframe and the personal computer, would be superseded by one in which computers would disappear into the objects that surround us in our daily life both at the office and at home. He further posited that the best computer is a quiet, invisible servant whose "calm technology" informs us but doesn't demand our focus or attention. His idea, often tagged "UbiComp," has borne fruit and we now have smart coffee pots, smart printers, smart copy machines and the like, all connected via a wired or wireless network. Users of some of the smart devices in our UbiComp world, such as mobile telephones, personal digital assistants, cameras, and camcorders, would benefit by knowing their location wherever they might be - whether it's in an open field, on a street surrounded by skyscrapers, or inside an apartment building. As we all know, conventional GPS receivers don't always work where we would like them to. In order for a UbiComp device to know its position anywhere and anytime, we need "ubiquitous positioning" or UbiPos. And like UbiComp, UbiPos should inform us but not demand our focus or attention. In this month's column, we take a look at the available technologies that might be used to supplement conventional GPS positioning and some initial testing that will eventually lead to a UbiPos world, one in which we can locate anyone, anything, anytime, anywhere. Numéro de notice : A2007-249 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28612 [article]

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