Centre de documentation
scientifique

The WAAS L5 signal: an assessment of its behavior and potential end use / H. Rho in GPS world, vol 20 n° 5 (May 2009)

Public [article]  inGPS world > vol 20 n° 5 (May 2009) . - pp 42 - 48 Titre : The WAAS L5 signal: an assessment of its behavior and potential end use Type de document : Article/Communication Auteurs : H. Rho, Auteur ; R.B. Langley, Auteur Année de publication : 2009 Article en page(s) : pp 42 - 48 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] signal GPS [Termes IGN] signal multidimensionnel [Termes IGN] test de performance [Termes IGN] Wide Area Augmentation System Résumé : (Auteur) The recent launch of the GPS Block IIR-20(M) satellite and the commissioning of its L5 demonstration payload herald the beginning of a bright new era in space-based positioning, navigation, and timing. The new satellite signal is anticipated to provide better-quality range measurements and possibly improve the tracking performance of a GPS receiver compared with current civil L1 and L2 signals through use of improved signal structures. The L5 signal will be standard on the future Block IIF and Block III satellites. However, some readers may be surprised to learn that L5 signals have been continuously transmitted by a pair of satellites for the past several years. The geostationary Earth-orbiting (GEO) satellites used by the U.S. Federal Aviation Administration's (FAA's) Wide Area Augmentation System to provide enhanced integrity and accuracy include not only an L1 payload but an L5 payload as well. While the WAAS L5 signals have been broadcast from space for some time, they did not come from a satellite in medium Earth orbit, and so it was necessary to include the demonstration payload on the GPS Block IIR-20(M) satellite to guarantee the L5 frequency filing with the International Telecommunication Union. There are some differences between the WAAS L5 signals and the future fully fledged GPS L5 signals. The WAAS L5 signals only use a single-channel carrier (there is no quadrature or Q channel) and the data rate is 250 bits per second (bps) rather than 50 bps. The WAAS signals are actually generated on the ground and relayed through the GEOs using a "bent pipe" approach. The FAA uses the L5 signals, in conjunction with the L1 signals, to compute ionospheric delays as part of the closed-loop control of the broadcast signals. Although the WAAS L5 signals are not yet intended for end users, can they be used now for positioning and navigation and, if so, are there any caveats? In this month's column, I am joined by one of my graduate students, Hyun-ho Rho, who has looked at the WAAS L5 transmissions, examining their signal strengths, multipath characteristics, and instrumental bias issues. Precise positioning performance of WAAS pseudoranges has also been assessed as an independent check on instrumental bias compensation by the WAAS control segment. The favorable results point to a future of the L5 signal, on both the WAAS satellites and the next-generation GPS satellites, which is bright indeed. Copyright Questex Media Group Numéro de notice : A2009-178 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29808 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
067-09051	SL	Revue	Centre de documentation	Revues en salle	Disponible

The GPS L2C signal: a preliminary analysis of data quality / Rodrigo Figueiredo Leandro in GPS world, vol 19 n° 10 (October 2008)

Public [article]  inGPS world > vol 19 n° 10 (October 2008) . - pp 42 - 47 Titre : The GPS L2C signal: a preliminary analysis of data quality Type de document : Article/Communication Auteurs : Rodrigo Figueiredo Leandro, Auteur ; R.B. Langley, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : pp 42 - 47 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] longueur d'onde [Termes IGN] qualité des données [Termes IGN] signal GPS [Termes IGN] utilisateur civil Résumé : (Auteur) 56 and counting. That's the number of GPS satellites that have been launched over the past thirty years beginning with the first prototype {Block I) satellite, space vehicle number 1, in February 1978. Ten Block I satellites were successfully launched between 1978 and 1985 to demonstrate the feasibility of GPS. The first satellite of the Block II operational constellation was launched in February 1989. The four year hiatus in launches was due, in part, to the Space Shuttle Challenger disaster as it had been planned to launch the operational satellites using the Shuttle. Following the accident, it was decided to continue with expendable rockets for GPS launches but to switch to the newly designed Delta II rocket. The pace of Block II launches was rapid with five launches of the original Block II design in 1989 and four in 1990 a modified, version of the Block II satellite - the IIA - was develloped, and between 1990 and 1997,19 Block IIAs were launched. The Block II and IIA satellites established the operational GPS constellation. Full operational capability was declared on April 27,1995. A new satellite was developed for replenishing the constellation as the earlier satellites were retired. Following an initial launch failure, twelve of the Block lIR satellites were launched between 1997 and 2004. All of the satellites in the Block I, Block II, Block IIA, and Block llR, constellations transmitted what are now called the legacy signals : tne C/A-code on the L1 frequency of 1575.42 MHz and the P-code on L1 and the L2 frequency of 1227.60 MHz.The P-code has been encrypted to yield the Y-code since January 1994, denying its direct access by most civil users. Since the C/A-code was only transmitted on the L1 frequency, civil users have had to rely on suboptimal semicodeless techniques for the dual-frequency operation necessary for direct cancellation of ionospheric biases. In 1998, Vice-President Al Gore announced that a new civil signal on L2 would be transmitted by future GPS satellites. This new signal-L2C-joined the legacy signals beginning with the launch of modernized Block llR satellite. Six of these blockllR-M satellites have been launched to date. In this month's column, we'll overview the characteristics of the new L2C signal and take a look at some of the analyses of received signals carried out by a team of researchers from the University of New Brunswick. Copyright Questex Media Group Inc Numéro de notice : A2008-397 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29390 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
067-08101	RAB	Revue	Centre de documentation	En réserve L003	Disponible

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]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
067-08031	RAB	Revue	Centre de documentation	En réserve L003	Disponible

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]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
067-06091	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Studies in the application of the Global Positioning System to differential positioning / R.B. Langley (1984)

Public Titre : Studies in the application of the Global Positioning System to differential positioning Type de document : Monographie Auteurs : R.B. Langley, Auteur ; Gerhard Beutler, Auteur ; D. Delikaraoglou, Auteur ; et al., Auteur Editeur : Fredericton [Canada] : University of New Brunswick Année de publication : 1984 Collection : Department of Surveying Engineering Technical Report num. 108 Importance : 90 p. Format : 21 x 29 cm Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] GPS en mode différentiel [Termes IGN] macromètre [Termes IGN] positionnement différentiel Index. décimale : 30.61 Systèmes de Positionnement par Satellites du GNSS Numéro de notice : 57026 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Recueil / ouvrage collectif Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=43862

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
57026-01	30.61	Livre	Centre de documentation	Géodésie	Disponible