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Online precise point positioning: a new, timely service from Natural Resources Canada / Y. Mireault in GPS world, vol 19 n° 9 (September 2008)

Public [article]  inGPS world > vol 19 n° 9 (September 2008) . - pp 59 - 64 Titre : Online precise point positioning: a new, timely service from Natural Resources Canada Type de document : Article/Communication Auteurs : Y. Mireault, Auteur ; P. Tetreault, Auteur ; François Lahaye, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : pp 59 - 64 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] Canada [Termes IGN] positionnement ponctuel précis [Termes IGN] serveur web [Termes IGN] temps réel [Termes IGN] traitement de données GNSS Résumé : (Editeur) Meliora sequamur - let us strive to improve. The words that the Roman poet Virgil wrote some 2,000 years ago could well be the watchwords of those scientists and engineers who today work to improve the accuracy, coverage, and timeliness of GPS-based positioning. They are particularly appropriate for those seeking to improve the technique of precise point positioning or PPP. PPP is a single-receiver positioning technique just like conventional pseudorange-based positioning, which takes place inside a receiver. However, the similarity stops there. PPP uses the receiver's very precise undifferenced carrier-phase observations together with very precise (and accurate) satellite orbits and clocks to achieve positioning accuracies at the few centimeter level or better. And unlike differential techniques such as real-time kinematic (RTK) positioning, all of the physical phenomena affecting the measurements must be very accurately modeled. These include solid earth tides, ocean-tide loading, transmitting and receiving antenna phase-center offsets and variations, carrier-phase wind-up, relativistic effects, and so on. With differential techniques, such effects are greatly reduced and typically become insignificant, especially on short baselines. PPP can be used to process data collected at a fixed (static) site or along a trajectory in kinematic mode or a mixture of the two - "stop and go" PPP. Although introduced in the late 1990s, PPP has only become more commonplace in the past few years, thanks, in part, to continued PPP development in government and university research labs. Several PPP processors are even available online. The precise satellite orbits and clocks required are provided by the International GNSS Service (IGS) and its worldwide tracking network and analysis centers. These products are supplied with some latency resulting in PPP normally being used as a post-processing technique with observations being processed some time after they are collected. However, over the past year or so efforts have been made to reduce the latency of some high-precision products. In particular, the ultra-rapid orbit and clock product of the Geodetic Survey Division of Natural Resources Canada (NRCan) is now being produced with a delay of only 90 minutes. Coupled with NRCan's online PPP engine, it provides positioning accuracies almost as good as the IGS final product, which is only available with a delay of about two weeks. In this month's column, we take a look at this new, timely service from the Great White North. Copyright Questex Media Group Inc Numéro de notice : A2008-384 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29377 [article]

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