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Multipath minimization method: mitigation through adaptive filtering for machine automation applications / L. Serrano in GPS world, vol 22 n° 7 (July 2011)

Public [article]  inGPS world > vol 22 n° 7 (July 2011) . - pp 42 - 48 Titre : Multipath minimization method: mitigation through adaptive filtering for machine automation applications Type de document : Article/Communication Auteurs : L. Serrano, Auteur ; D. Kim, Auteur ; R. Langley, Auteur Année de publication : 2011 Article en page(s) : pp 42 - 48 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] antenne GNSS [Termes IGN] appariement de formes [Termes IGN] filtrage du rayonnement [Termes IGN] guidage de véhicules [Termes IGN] phase GPS [Termes IGN] trajet multiple Résumé : (Auteur) [...] The best way to reduce the effects of multipath is to try avoiding it in the first place by siting the receiver's antenna as low as possible and far away from potential reflectors. But that's not always feasible. [...] At a static site, with an unchanging multipath environment, the signal reflection geometry repeats day to day and the effect of multipath can be reduced by sidereal filtering or "stacking" of coordinate or carrier-phase-residual time series. However, this approach is not viable for scenarios where the receiver and antenna are moving such as in machine control applications. Here an alternative approach is needed. In this month's column, I am joined by two of my UNB colleagues as we look at a technique that uses a pair of antennas on a moving vehicle together with a sophisticated mathematical model, to reduce the level of multipath on carrier-phase observations and thereby improve the accuracy of the vehicle's position. Numéro de notice : A2011-326 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31105 [article]

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Improving long-range RTK: getting a better handle on the biases / D. Kim in GPS world, vol 19 n° 3 (March 2008)

Public [article]  inGPS world > vol 19 n° 3 (March 2008) . - pp 50 - 56 Titre : Improving long-range RTK: getting a better handle on the biases Type de document : Article/Communication Auteurs : D. Kim, Auteur ; R.B. Langley, Auteur Année de publication : 2008 Article en page(s) : pp 50 - 56 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] correction atmosphérique [Termes IGN] GPS en mode cinématique [Termes IGN] phase GPS [Termes IGN] positionnement cinématique en temps réel [Termes IGN] propagation ionosphérique [Termes IGN] propagation troposphérique [Termes IGN] résolution d'ambiguïté Résumé : (Editeur) Scientists and engineers continue to improve high-accuracy GPS positioning techniques - techniques pioneered a quarter of a century ago. The first GPS satellite, SVN01/PRN04, was launched from Cape Canaveral on February 22, 1978. And between 1978 and 1985, the U.S. Air Force orbited nine more prototype or Block I satellites to test key technologies before deploying the operational constellation. Surveyors and geodesists were among the earliest users of the Block I satellites. Using the satellite signals, they developed accurate positioning techniques based on the use of carrier-phase observations - about two orders of magnitude more precise than code measurements. To reduce the effect of biases and errors in the measurements, they developed the concepts of between-satellite and between-receiver single differencing of the carrier-phase data as well as double and triple differencing. Raw measurements were recorded by receivers and then post-processed to obtain receiver coordinates. Clever approaches were developed to handle the integer ambiguity of the carrier phases. With the launch of the Block II satellites beginning in 1989, further improvements in positioning accuracy and efficiency became possible, including real-time carrier-phase based positioning with a radio link between a reference receiver and a remote receiver. This technique became known as real-time kinematic or RTK, as it permitted the remote receiver to rove and occupy different points in a single positioning exercise. But carrier-phase ambiguity resolution issues coupled with inaccurately modeled satellite orbit and atmospheric effects has limited consistent single-baseline RTK operation between reference and rover receivers to tens of kilometers. On longer baselines, inaccurate modeling can result in significant positioning errors. Network RTK, using simultaneously operating reference stations to better determine error corrections, can extend the area of coverage of RTK but it, too, has limitations. In this month's column, I am joined by my colleague Don Kim who has developed an innovative approach to long-range RTK. We describe how accurate modeling of atmospheric effects coupled with an ionosphere-free ambiguity resolution process results in successful long-range RTK that can be implemented in either single-baseline or network mode. Has the ultimate RTK approach been developed? Probably not. But we're getting closer. Copyright Questex Media Group Inc Numéro de notice : A2008-162 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29157 [article]

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Phase wind-up analysis: assessing real-time kinematic performance / D. Kim in GPS world, vol 17 n° 9 (September 2006)

Public [article]  inGPS world > vol 17 n° 9 (September 2006) . - pp 58 - 64 Titre : Phase wind-up analysis: assessing real-time kinematic performance Type de document : Article/Communication Auteurs : D. Kim, Auteur ; R.B. Langley, Auteur ; L. Serrano, Auteur Année de publication : 2006 Article en page(s) : pp 58 - 64 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] antenne GPS [Termes IGN] GPS en mode cinématique [Termes IGN] mesurage de phase [Termes IGN] phase GPS [Termes IGN] positionnement cinématique en temps réel Résumé : (Auteur) [...] RTK systems, in common with other techniques, are susceptible to biases and errors such as ionospheric and tropospheric refraction along with line-of-sight-dependent phase-measurement effects including multipath, antenna phase-center variation, and carrier-phase phase wind-up. This latter phenomenon may not be familiar to all readers. It is a bias introduced into carrier-phase measurements by the rotation of a GPS receiver’s antenna. There is also a contribution from the rotation of a GPS satellite’s antenna as it orbits about the Earth. In developing an RTK-based vehicle navigation system at the University of New Brunswick (UNB), we have observed a few instances where the phase wind-up due to rotation of the rover receiving antenna can significantly degrade system performance. In this month’s column, we’ll look at carrier-phase wind-up, introducing three wind-up observables that allowed us to perform qualitative assessments of its effects on the UNB RTK system. One motivation behind such an assessment is to determine whether or not we need to proceed to the next step of implementing algorithms to correct for the effects of phase wind-up. I am joined by Dr. Don Kim, the chief architect and developer of the UNB RTK system, and graduate student Luis Serrano. Copyright Questex Media Group Inc Numéro de notice : A2006-418 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28142 [article]

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